Chlorine Dioxide

Occupational and Residential Exposure Assessment

Case 4023

Timothy Leighton

Office of Pesticide Programs

Antimicrobials Division

U.S. Environmental Protection Agency

  SEQ CHAPTER \h \r 1 1200 Pennsylvania Avenue, NW

Washington, DC 20460

August 2, 2006

TABLE OF CONTENTS

  TOC \f  1.0	INTRODUCTION	  PAGEREF _Toc121537099 \h  6 

1.1      	Purpose	  PAGEREF _Toc121537100 \h  6 

1.2	Criteria for Conducting Exposure Assessments	  PAGEREF _Toc121537101
\h  6 

1.3	Chemical Identification	  PAGEREF _Toc121537102 \h  6 

1.4	Physical/Chemical Properties	  PAGEREF _Toc121537103 \h  7 

2.0	USE INFORMATION	  PAGEREF _Toc121537104 \h  7 

2.1	Formulation Types and Percent Active Ingredient	  PAGEREF
_Toc121537105 \h  7 

2.2	Summary of Use Pattern and Formulations	  PAGEREF _Toc121537106 \h 
8 

3.0	SUMMARY OF TOXICITY CONCERNS RELATING TO EXPOSURES	  PAGEREF
_Toc121537107 \h  15 

3.1	Acute Toxicology	  PAGEREF _Toc121537108 \h  15 

3.2	Summary of Toxicity Concerns Relating to Exposures	  PAGEREF
_Toc121537109 \h  1 5

3.3	FQPA Considerations	  PAGEREF _Toc121537110 \h  1 6

4.0	RESIDENTIAL AND PUBLIC ACCESS PREMISES	  PAGEREF _Toc121537111 \h 
17 

4.1	Summary of Registered Uses	17

4.2	Residential Exposure/Risk Pathway	  PAGEREF _Toc121537115 \h  1 7

4.2.1	Residential Handler Exposure	  PAGEREF _Toc121537116 \h  1 7

	4.2.1.1	Residential Handler Dermal Exposure and Risk                			
            PAGEREF _Toc121537116 \h  1 7

4.2.1.2	Residential Handler Inhalation Exposure and Risk                
			            PAGEREF _Toc121537116 \h  1 7

4.2.2	Residential Post Application Exposure	  PAGEREF _Toc121537117 \h 
22 

4.2.2.1	Hard Surface/Floor	  PAGEREF _Toc121537118 \h  23 

4.2.2.2	Ventilation Systems	  PAGEREF _Toc121537119 \h  29 

4.2.2.3	Continuous Release (Gas) Deodorizer 	30

4.2.2.4	Swimming Pools & Spas	32

4.2.3	Data Limitations/Uncertainties	  PAGEREF _Toc121537120 \h  32 

5.0	RESIDENTIAL AGGREGATE RISK ASSESSMENTS AND RISK CHARACTERIZATION	 
PAGEREF _Toc121537121 \h  33 

6.0	OCCUPATIONAL EXPOSURE AND RISK	  PAGEREF _Toc121537124 \h  33 

6.1 	Occupational Handlers	  PAGEREF _Toc121537125 \h  33 

	6.1.1   Dermal Handler Exposures	  PAGEREF _Toc121537125 \h  33 

	6.1.2   Inhalation Handler Exposures	43

6.2	Occupational Post Application Exposure	  PAGEREF _Toc121537126 \h 
43 

	6.2.1   Dermal Postapplication/Bystander Exposures	43

	6.2.2   Inhalation Postapplication/Bystander Exposures	43

6.3	Data Limitations/Uncertainties	48

7.0	 REFERENCES	50

APPENDIX A: Summary of CMA data and PHED	52

APPENDIX B: Input/Output from E-FAST/CEM	55

 

EXECUTIVE SUMMARY

		

This document contains the occupational and residential exposure
assessment for industrial, commercial, residential, and agricultural
premises and equipment uses of chlorine dioxide.  Both sodium chlorite
and sodium chlorate are used as a precursor in the generation of
chlorine dioxide.  The handler exposures to sodium chlorite are also
included in this document because the same toxicological endpoints are
used for both chlorine dioxide and sodium chlorite.  The handler
exposures to sodium chlorate itself are assessed in a separate document
(USEPA, 2005b). 

Chlorine dioxide, sodium chlorite, and sodium chlorate are active
ingredients in numerous products used in the control of bacteria, fungi,
and algal slimes.  In addition, they are used as material preservatives
and as disinfectants.  At this time, these products are intended for
agricultural premises and equipment, commercial, industrial, medical and
residential use.  The agricultural uses include the disinfection of hard
surfaces and equipment (such as hatching facilities and mushroom houses)
and water systems (such as chiller water and humidification water in
poultry houses).  Commercial, industrial, and medical uses include
disinfection of heating ventilating and air-conditioning (HVAC) systems,
hard surfaces (e.g., floors, walls, and laboratory equipment), water
systems, pulp/paper mills, and food rinses.  Residential uses include
disinfection of hard surfaces (e.g., floors, bathrooms), and HVAC
systems.  Concentrations of chlorine dioxide and sodium chlorite in
products range from 0.1% to 80%.  Most formulations are in liquid form. 
However, chlorine dioxide and sodium chlorite are also available as
tablets, ready-to-use solutions, dusts, and sachets.  The application
rates used in this assessment were the maximum application rates
recommended on the product labels.

Acute toxicity categories for chlorine dioxide include Category III for
oral and dermal and Category II for inhalation.  The toxicological
endpoints selected to assess chlorine dioxide and sodium chlorite risks
include short- and intermediate-term dermal and ingestion exposure.  The
short- and intermediate-term NOAEL for both the dermal and oral routes
is 3 mg/kg/day.  For the dermal route, 100 percent dermal absorption is
assumed.  The oral NOAEL is based on depression of serum T4 levels in
pups from dosed maternal rats and delays in development of locomotor and
exploratory behavior activities.  For the oral and dermal route of
exposure, an uncertainty factor or “target” margin of exposure (MOE)
of 100 is based on 10x for differences among humans (intraspecies
variability) and 10x for differences between the test animals and humans
(interspecies extrapolation).  Thus, MOEs of greater than 100 are above
the Agency’s target MOE for oral and dermal routes for occupational
and residential uses.

The inhalation route of exposure to chlorine dioxide is assessed for
three distinct subpopulations:  (1) occupational exposures (8 hours/day,
5 days/week), (2) one-time exposures for residential uses (e.g., HVAC
systems, mopping floors, etc), and (3) long-term exposure for continuous
release products in the home (24 hours/day, 7 days/week).  Several
animal studies were used to develop reference concentrations (RfCs). 
The effects seen at various concentrations include rhinorrhea, altered
respiration, respiratory infection, bronchial inflammation, alveolar
congestion and hemorrhage, vascular congestion, and peribronchiolar
edema.  Readers are referred to USEPA (2005a) for a detailed review of
the effects seen at specific concentrations and exposure durations along
with the derivation of the RfC.  In summary, the occupational RfC is
determined to be 0.003 ppm and represents an 8-hour time weighted
average (TWA).  The one-time residential exposure scenario is
represented by the RfC of 0.05 ppm and the RfC for long-term, continuous
exposure is 0.00007 ppm.  The RfC methodology incorporates the
uncertainty factors into the concentration, and therefore, margins of
exposure (MOE) are not used to express the risks.  For inhalation, the
RfC is compared directly to the air concentration of interest. 
Inhalation risks are of concern if the air concentrations people are
exposed to exceed the RfC.

The exposure scenarios selected as representative uses of chlorine
dioxide to be assessed in the risk assessment are presented in the table
at the end of this section.  These scenarios were based on examination
of product labels describing uses for the product. Several different
sources of handler exposure data were used to assess occupational and
residential chlorine dioxide risks.  Data from both the proprietary
Chemical Manufacturers Association (CMA) antimicrobial exposure study
and the Pesticide Handlers Exposure Database (PHED) were used.  In
addition, chemical-specific data were available to assess inhalation
exposures for the following uses:  HVAC, carpet, automobiles, and
OSHA’s Integrated Management Information System (IMIS) for various
industrial uses.

Residential Risks

For residential dermal exposures, the calculated MOEs for handlers are
less then the target MOE of 100 for the swimming pool & spa application
scenarios (i.e., for placing tablets into swimming pools/spas, the
dermal MOE = 46).  Note:  The risk may be over stated because the dermal
absorption was assumed to be 100 percent due to the lack of a dermal
absorption study or dermal route-specific toxicity study.  If the
applicator wears gloves, the dermal risk would be mitigated (i.e. MOE is
500) The inhalation exposures to the handlers are not of concern.  

The calculated dermal and incidental oral MOEs for post application
exposure were not of concern for all scenarios.  The post application
inhalation MOEs were not of concern except for dust applications to
carpets.  Although the inhalation risks were indeterminate for the
carpet use, additional monitoring data are warranted based on the air
concentration measurements available 3 to 4 hours post treatment.   

One product has been identified that is registered as a continuous
release of chlorine dioxide gas in homes.  The product is packaged as a
pouch or sachet.  A bounding estimate of air concentration is presented
based on the application rate and the label-referenced longevity of the
pouches/sachets.  The theoretical constant air concentration would be
0.52 ppm assuming no air exchange and no build up of chlorine dioxide
over time because of the short half-life.  The RfC for long-term
continuous exposure is 0.00007 ppm.  Therefore, the theoretical
concentration from the product’s release is of concern for indoor
uses.  Before any refinements to these air concentration estimates are
attempted, it should be determined if the product’s efficacy can be
maintained at the RfC of ~0.00007 ppm.

Occupational Risks

For occupational dermal exposures, calculated MOEs less than the target
dermal MOE of 100 were found for the following handler scenarios:

Agricultural Premises and Equipment

application to hard surfaces via low-pressure hand wand (MOE = 31)

application to hard surfaces via mopping (MOE = 70)

foam applicator to animal transport vehicles/tractor trailer (MOE = 52)

Food Handling, Commercial/Institutional, and Medical Premises and
Equipment

application to hard surfaces via mopping (MOE = 66 for commercial and 3
for medical)

Inhalation exposures/risks were not assessed separately for the
handlers.  Instead, the occupational inhalation handler exposures are
combined as part of the full work day for handler/bystanders to be
comparable to EPA’s inhalation toxicological endpoint which is based
on an 8-hour TWA.  For the peak, short-term exposures to chlorine
dioxide gas experienced during mixing/loading and/or system
leaks/failures, EPA will rely on the American Conference of Governmental
Industrial Hygienists (ACGIH) Short-term Exposure Limit (STEL) and
Immediately Dangerous to Life or health (IDLH) to mitigate risks.  

For most of the bystander/post application occupational scenarios,
dermal exposures are not expected to occur or are expected to be
negligible based on the relatively low application rates and chemical
properties (e.g., volatility and short ½ life) of chlorine dioxide,
sodium chlorite and sodium chlorate.  However, the inhalation risks for
the bystander/post application occupational exposures are of concern
using the EPA’s selected inhalation toxicological endpoint (RfC).  The
occupational RfC, 0.003 ppm, is below the limit of detection for
chlorine dioxide.  Based on OSHA’s IMIS data available for chlorine
dioxide, all air concentration measurements, even those that were
nondetect, are above the RfC.  Reconciliation of the EPA risk-based RfC
and current OSHA standards will be made during the regulatory decision
phase of the Reregistration Eligibility Decision (RED) for chlorine
dioxide.

There are a number of uncertainties associated with this assessment (see
Sections 4.4.3 and 6.3).  In general, conservative values were used in
cases where data were lacking.  Assessments for these scenarios should
be considered as screening-level.

Use Scenarios Based on Product Labels for Chlorine Dioxide,

Sodium Chlorite and Sodium Chlorate

Use Site	Scenario

Agricultural Premises and Equipment	Low pressure hand wand, fog, mop,
spray, foaming wand for hard surfaces

Fogging (e.g., egg houses)

Food Handling, Commercial/ Institutional, Medical	Mop and spray on hard
surfaces

Fruit & vegetable dip

Residential and Public Access	Trigger-pump sprayer and mop to hard
surfaces

HVAC reentry

Solid tablets for swimming pools and spas

Continuous release deodorizer

Human Drinking Water Systems	Metering pump for potable water and storage
systems

Material Preservatives	Metal working fluids (MWF)

Industrial Processes and Water Systems	Metering pump to pulp and paper
white water systems

Liquid pour to oil systems

Swimming Pools and Aquatic Areas	Liquid pour to non-potable water
systems (e.g., retention ponds and decorative fountains)

Tablets in the circulation systems of swimming pools & spas

HVAC Systems	Spray and fog of ventilation systems (e.g., duct work)



1.0	INTRODUCTION tc "1.0	INTRODUCTION" 

	1.1       Purpose   tc "	1.1       Purpose  " \l 2 

In this document, EPA presents the results of its review of the
potential human health effects of occupational and residential exposure
to chlorine dioxide, including the releases of chlorine dioxide from
sodium chlorite and sodium chlorate applications.  This information is
for use in EPA's development of the chlorine dioxide Reregistration
Eligibility Decision (RED) document. 

	1.2	Criteria for Conducting Exposure Assessments  tc "1.2	Criteria for
Conducting Exposure Assessments " \l 2 

An occupational exposure assessment is required for an active ingredient
if (1) certain toxicological criteria are triggered and (2) there is
potential exposure to handlers (mixers, loaders, applicators, etc.)
during use or to persons entering treated sites after application is
complete.  For chlorine dioxide, both criterions are met.  Note:  The
toxicity of sodium chlorite has been assumed to be equivalent to that of
chlorine dioxide.

	1.3	Chemical Identification  tc "1.3	Chemical Identification " \l 2 

Three chemicals are considered in this document: chlorine dioxide,
sodium chlorite, and sodium chlorate.  Products containing chlorine
dioxide or sodium chlorite have been included in this risk assessment. 
Risks/exposures to sodium chlorate itself have been assessed in a
separate document: “Sodium Chlorate: Occupational and Residential
Exposure Assessment of Antimicrobial Uses for the Reregistration
Eligibility Decision Document” (USEPA, 2005).  However, risks to
chlorine dioxide released from sodium chlorate applications are included
in the scope of this document.  Table 1.1 presents the chemical
identification information for the three chemicals. 

Table 1.1.  Chemical Identification Information for Chlorine Dioxide,
Sodium Chlorite, and Sodium Chlorate

	Chlorine Dioxide	Sodium Chlorite	Sodium Chlorate

OPP Chemical Code	020503	020502	073301

CAS Number	10049-04-4	7758-19-2	7775-09-9

Molecular Formula	ClO2	NaClO2	NaClO3



	1.4	Physical/Chemical Properties  tc "1.4	Physical/Chemical Properties
" \l 2 

Table 1.2 shows physical/chemical characteristics that have been
reported for chlorine dioxide and sodium chlorite.

Table 1.2.  Physical/Chemical Properties of Chlorine Dioxide and Sodium
Chlorite

Property	Chlorine Dioxide	Sodium Chlorite

Molecular Weight	67.45 g/mol	90.45 g/mol

Color	Yellow to Reddish Yellow	White

Melting Point	-59oC	180-200oC (decomposes)

Boiling Point	11oC	n/a

Odor	Strongly pungent, chlorine-like	n/a

Physical State	Gas at room temperature	Solid

Density	1.64 g/ml at 0oC (liquid)

1.614 g/ml at 10o C (liquid)	2.468 g/ml (as a solid)

Vapor Pressure	490 mm Hg (0oC)

>760 mm Hg (25oC)	n/a

Stability	Unstable, estimated half life in water ~ 25 minutes	n/a

Solubility (water)	3.01 g/L at 25oC and 34.5 mmHg	390 g/L at 30oC

References:  ATSDR 2004 and Gates 1998

2.0	USE INFORMATION tc "2.0	USE INFORMATION" 

	2.1	Formulation Types and Percent Active Ingredient  tc "2.2
Formulation Types and Percent Active Ingredient " \l 2 

Concentrations of chlorine dioxide and sodium chlorite in products range
from 0.1% to 80%.  Most formulations are in liquid form.  However,
chlorine dioxide and sodium chlorite are also available as tablets,
wettable powders, and water-soluble packets.  Registered uses include
use as a fruit/vegetable rinse, potable water treatment, hard surface
disinfectant, disinfectant of ventilation systems, foggers, material
preservatives (e.g., water based cutting oils), industrial systems
(e.g., water cooling towers), and non-potable water systems.

	2.2	Summary of Use Pattern and Formulations  tc "2.2	Summary of Use
Pattern and Formulations " \l 2 

Chlorine dioxide and sodium chlorite are active ingredients in numerous
products used in the control of bacteria, fungi, and algal slimes.  In
addition, chlorine dioxide and sodium chlorite are used as material
preservatives and as disinfectants.  At this time, products containing
chlorine dioxide and sodium chlorite are intended for agricultural,
commercial, industrial, medical, and residential use.  The agricultural
uses include the disinfection of hard surfaces and equipment (such as
hatching facilities and mushroom houses) and water systems (such as
chiller water and humidification water in poultry houses).  Commercial,
industrial, and medical uses include disinfection of ventilation
systems, hard surfaces (e.g., floors, walls, and laboratory equipment),
water systems, pulp/paper mills, and food rinses.  Residential uses
include disinfection of hard surfaces (e.g., floors, bathrooms), and
ventilation systems along with a pool/spa water circulation system
treatment.

The Agency determines potential exposures to handlers of the product by
considering exposure scenarios from the various application methods that
are plausible, given the label uses.  Based on review of the product
labels and the various uses identified, several potential exposure
scenarios were chosen for this risk assessment.  Those scenarios, the
methods of application, and the maximum application rates are provided
in Tables 2.1 through 2.3. Tables of use scenarios are provided for
chlorine dioxide, sodium chlorite, and sodium chlorate.  Representative
uses were chosen from all of the uses for all three chemicals, based on
application method, rate and potential exposures.  After review of the
labels, it was determined that sodium chlorite and chlorine dioxide
labels represent the highest application rates that produce chlorine
dioxide.  Application rates were determined in pounds active ingredient
per gallon (lb ai/gal).  It is assumed that rates of sodium chlorite
produce equivalent rates of chlorine dioxide (e.g., 0.08 lb ai/gal of
sodium chlorite solution equals 0.08 lb ai/gal of chlorine dioxide). 
The density of chlorine dioxide in liquid form (1.642 g/cm3 or 13.7
lb/gal) was used to determine the lbs ai/gal.  It was assumed that a
100% active ingredient solution would contain 13.7 lb ai/gal.  This
ratio was then used to determine the lb ai/gal for other products, by
multiplying the % ai provided on the label by a factor of 0.137
(13.7/100).  For some of the sodium chlorite labels, the application
rate was not provided in terms of lbs ai/gal.  Therefore, a ratio of lbs
ai/gal to % ai was used from another label (0.1032; EPA Reg. 1757-96). 
This ratio was multiplied by the % ai to estimate the lbs ai/gal. 

Table 2.1.  Use Scenarios and Methods of Application Based on Product
Labels for Chlorine Dioxide

Uses	Representative Exposure	EPA Reg. # Associated with Maximum Exposure
Application Rate Associated with Maximum Exposure 

(lb a.i./gallon)	Residual Chlorine Dioxide Level (ppm)

Use Site Category I (Agricultural Premises and Equipment)a

Application to hard surfaces (e.g., animal rearing and confinement
facilities; horticulture uses; mushroom facilities)	Low-pressure hand
wand	Liquid concentrate

9150-2	0.014	1000

	fog (1 hour REIb)

0.014	1000

	mop

spray

0.018	1250

	dip (e.g., litter boxes)

0.014	1000

	shampoo	Liquid concentrate

9804-1	0.008	500

	foaming wand  (animal transport vehicles; agricultural storage
facilities; containers, trailers, rail cars, vessels)	Liquid concentrate
9150-11	0.025	not provided

Water systems

	chiller water

liquid pour	Liquid concentrate

9150-2	0.001	40

	humidification water in poultry houses

mist or fog (1 hour REI)	Liquid concentrate

9150-2	0.001	40

Use Site Categories II (Food Handling), III (Commercial/Institutional),
and V (Medical)

Application to hard surfaces with food contact in Food processing
plants; Hospitals (e.g., water bath incubators, autoclaves); Public
places (e.g., restaurants, hotel/motel rooms); Medical/Dental offices
spray 	9150-2 Liquid Concentrate	0.014	1000

Application to hard surfaces without food contact in Food processing
plants; Hospitals (e.g., water bath incubators, autoclaves); Public
places (e.g., restaurants, hotel/motel rooms); Medical/Dental offices
mop or spray	9150-10 active

Liquid concentrate (10589-3 transferred)	0.019	not provided

Water systems	Canner retort and pasteurizer cooling water

liquid pour; chemical feed pump or injector	9804-1

Liquid concentrate	0.00007	5

	Humidification water on stored potatoes

mist or fog (1 hour REI after fogging)	9804-5

Liquid concentrate	0.003	200

	Potable water, ice made from potable water

liquid pour	9804-5

Liquid concentrate	0.017	not provided

Ventilation systems (HVAC)	Ventilation systems (HVAC)

spray or fog  (1hour REI after fogging)	9804-1

Liquid concentrate	0.007	500

Fruit/Vegetable rinses	dip	Liquid concentrate

9150-2	0.002	not provided

Use Site Category IV (Residential & Public Access)

Application to hard surfaces (e.g.,  floors, carpet, bedding, furniture)
Pump-trigger	9804-3

Liquid concentrate	0.002	not provided

Evaporative cooler	liquid pour	9150-11

Liquid concentrate	0.0007	not provided

Ventilation systems (HVAC)	Handler not assessed, only post application 
(1 hour REI after fogging)	9804-1

Liquid concentrate	0.007	500 ppm

Decorative pools, fountains, and water displays	liquid pour	9150-11

Liquid concentrate	0.0001	not provided

Continuous release deodorizer	 Handler not assessed, only post
application inhalation	70060-12

Pouch/Sachet	NA	not provided

Use Site Category VI (Human Drinking Water Systems)

Water Treatment and water storage systems	liquid pour and/or metering
pump	9804-1

Liquid concentrate	0.008 (to treat water storage system of aircraft,
boats, RVs, offshore oil rigs)	500



	0.00007 (to treat stored potable water)	5

Use Site Category VII (Material Preservatives)

Industrial application to water based cutting oils

(MWF)	liquid pour and/or metering pump	9150-2

Liquid concentrate

(5% ai assume density 8 lb/gal)	batch method: 0.0001 (per week)

continuous method: 

8E-7 (per day)

badly contaminated systems:  4E-6 (slug dose)	not provided

Use Site Category VIII (Industrial Processes and Water Systems)

Application to hard surfaces (e.g.,  evaporative cooler)	liquid pour
and/or metering pump	9150-11

Liquid concentrate	0.0007	not provided

Water filtration systems, sand beds, gravel beds, charcoal filters
(e.g., to control mollusks)	liquid pour and/or metering pump	9150-2

Liquid concentrate	0.03	2000

Paper mill systems	liquid pour and/or metering pump	9150-2

Liquid concentrate	3.1 lb ai/100 tons paper produced	not provided



9804-1

Liquid concentrate	0.00007	5

Oil wells	liquid pour and/or metering pump	9150-2

Liquid concentrate	0.069	5000

Use Site Categories XI and XII (Swimming Pools and Aquatic Areas)

Non-potable water systems (e.g., retention basins and ponds, decorative
pools and fountains)	liquid pour and/or metering pump	9150-11

Liquid concentrate 	0.00001

(18 fl oz x 0.72% ai per 100 gallons water)	10

Use Site Category XIII (HVAC)

Ventilation systems	spray or fog (1hour REI after fogging)	9804-1

Liquid concentrate	0.007	500

a	Applications are made in agricultural settings including, but not
limited to, mushroom houses, poultry facilities, animal facilities, and
hatching facilities.

b	REI = Reentry Interval

Table 2.2.  Use Scenarios and Methods of Application Based on Product
Labels for Sodium Chlorite

Uses	Representative Exposure	EPA Reg. # Associated with Maximum Exposure
Application Rate Associated with Maximum Exposure (lb a.i./gallon)
Residual Chlorine Dioxide Level (ppm)

Use Site Category I (Agricultural Premises and Equipment)a

Application to hard surfaces (e.g., Animal rearing and confinement
facilities; Horticulture uses; Mushroom facilities)	low-pressure hand
wand	74602-02 Liquid concentrate

70060-18 tablet	0.015

0.002	1000

100

	high pressure hand wand	74602-02 Liquid concentrate	0.0003	20

	spray or fog (1 hour REI after fogging)	74602-02 Liquid concentrate
0.0083	500

	shampoo	74602-02 Liquid concentrate	0.008	500

Water supply (e.g., drinking water, humidification water in poultry
houses)	liquid pour	74602-02 Liquid concentrate	0.0006	40

Use Site Categories II (Food Handling), III (Commercial/Institutional),

and V (Medical)

Application to hard surfaces with food contact in Food processing
plants; Hospitals (e.g., water bath incubators, autoclaves); Public
places (e.g., restaurants, hotel/motel rooms); Medical/Dental offices
foam	21164-8

Liquid concentrate	0.002	Not provided

	spray or dip	74602-02

Liquid concentrate	0.003	200

Application to hard surfaces without food contact in Food processing
plants; Hospitals (e.g., water bath incubators, autoclaves); Public
places (e.g., restaurants, hotel/motel rooms); Medical/Dental offices
(cont.)	spray

mop

sponge

immersion	70060-19

tablet	0.005	200

	sprayer or dilution device	74986-1

WP

100

	spray

mist

sponge	21164-3

 Liquid concentrate	0.08	Not provided

	fog/mist (15 min REI)	21164-3

Liquid concentrate	0.007	Not provided

	RTU packet	70060-12 

RTU packet	**	Not provided

	RTU packet	70060-13

RTU packet	0.04 lb ai

 (20 lb ai/day)	Not provided

Water systems (e.g., potable water)	liquid pour	9150-7

Liquid concentrate	0.002	150



70060-16

tablet	0.000004	Not provided

Fruit/vegetable rinse	dip	74602-02

 Liquid concentrate	0.011	1200

Air Deodorizer	fog (15 min REI)	74602-3

Liquid concentrate	0.007	Not provided

Carpet deodorizer	duster	70060-4 

Dust	0.0001 lb ai/ft2	Not provided

Use Site Category IV (Residential & Public Access)

Application to hard surfaces (e.g.,  bathrooms, laundry rooms, trash
cans)	RTU packet	70060-12

RTU packet	**	Not provided

Room/Surface deodorizer	spray, sponge	74602-02

Liquid concentrate	0.004	Not provided

Carpet deodorizer	duster	70060-4

Dust	0.0001 lb ai/ft2	Not provided

Residential and Industrial Ion Exchange Resin Beds	tablet	70060-19

tablet	0.003 lb ai/ft3	Not provided

Use Site Category VI (Human Drinking Water Systems)

Water Treatment and water storage systems	sprayer or dilution device
74986-1 (potable water systems)

WP	Not provided	100

	liquid pour and/or metering pump 	5382-46 (potable water systems)

Liquid concentrate	0.00008	5



74602-02 (aircraft, boats, RVs, offshore oil rigs)

Liquid concentrate	0.008	500

	tablet	70060-22 (emergency disinfection of drinking water)

tablet	0.0002	Not provided

Use Site Category VII (Material Preservatives)

Pulp/Paper products

Polymers

Emulsions

Adhesives

Pigment slurries	liquid pour and/or metering pump 	74655-2

Liquid concentrate	Not provided	1000

Use Site Category VIII (Industrial Processes and Water Systems)

Water cooling systems (e.g., commercial and industrial recirculation
cooling water systems, once through cooling water systems)	tablet
70060-16

tablet	0.000004	Not provided

	water soluble packet 	72874-1

WSP (bag)	0.0002	Not provided

Recycle wash water systems	tablet-canister feed or tank addition
70060-16

tablet	0.00009	Not provided

Oil field secondary recovery operations	liquid pour and/or metering pump
21164-3

Liquid concentrate	0.007	Not provided

Paper mills 	liquid pour and/or metering pump 	74602-3

Liquid concentrate	0.0001 lb ai/gal white water (3.44 lb ai/100 ton
paper produced)	Not provided

Use Site Category XI (Swimming Pools)

Swimming pools & Spas 

(place 2 tablets in skimmer and 2 tablets in hair/lint basket to clean
pool circulation system)

	tablet	70060-20

tablet	4 tablet /10,000 gal 

(Pool tablet is 100 g x 4 tablets x 20%ai = 80 g ai/10,000 gal = 1.8E-5
lb ai/gal)	Not provided

Use Site Category  XII (Aquatic Areas)

Water Treatment and water storage systems (e.g., municipal water,
non-potable water used with cut flowers)	liquid pour and/or metering
pump	53345-23

Liquid concentrate	Not provided	2



	sprayer or dilution device	74986-1

WP	Not provided	100

** Label lists various application rates: refrigerator: 0.006 lb ai;
shoes: 0.0006 lb ai; hamper: 0.01 lb ai/ft2; basement: 0.0002 lb ai/ft2;
gym locker: 0.0002 lb ai/ft3; cars: 0.006 lb ai; boats: 0.0002 lb
ai/ft3; athletic bag: 0.0003 lb ai/ft3; trash can: 0.006 lb ai; trash
bag: 0.006 lb ai; diaper pail: 0.002 lb ai; litter box/pet area: 0.0001
lb ai

Table 2.3.  Use Scenarios and Methods of Application Based on Product
Labels for Sodium Chloratea

Uses	Representative Exposure	EPA Reg. # Associated with Maximum Exposure
Application Rate Associated with Maximum Exposure (lb a.i./gallon)
Residual Chlorine Dioxide Level (ppm)

Use Site Categories I (Agricultural), II (Food Handling), III
(Commercial/Institutional), VIII (Industrial Processes and water
systems), XII (Aquatic areas)

Water systems	Agricultural water uses	49620-4	--a	2 

	Pasteurizer./Cannery/Retort	49620-4	--a	0.4

	Cooling towers; wastewater	10707-32	--a	800

	Pulp and Paper	53345-17/-18	--a	4000

	Gas/oil injection	49620-4	--a	3000

	Ultrasonic tank water and photo processing was water	49620-4	--a	5

Aquatic areas (e.g., lakes and reservoirs)

49650-4	--a	5

a Table developed from Table 2 of the Sodium Chlorate ORE Document;
application rates were not provided

3.0	SUMMARY OF TOXICITY CONCERNS RELATING TO EXPOSURES tc "3.0	SUMMARY
OF TOXICITY CONCERNS RELATING TO EXPOSURES" 

3.1	Acute Toxicology  tc "3.1	Acute Toxicology " \l 2 

	Chlorine dioxide (CAS No. 10049-04-4) is used as a disinfectant in a
variety of sites, including drinking water, swimming pools, fruits and
vegetables, and household uses.  Sodium chlorite and sodium chlorate
products release chlorine dioxide and are included in this assessment as
well.  

	Table 3.1 presents the acute toxicity categories as outlined in the
toxicity memorandum dated February 15, 2005 (USEPA, 2005a). 

Table 3.1. Acute Toxicity Categories for Chlorine Dioxide

Study Type	Toxicity Categorya

Acute Oral Toxicity	II

Acute Dermal Toxicity	III

Acute Inhalation Toxicity	II

Primary Eye Irritation	III

Primary Dermal Irritation	II

Dermal Sensitization	No acceptable sensitization study available

	a The available acute studies are all graded as acceptable.  An
acceptable dermal sensitization study is not available in the database. 
 	

	

3.2	Summary of Toxicity Concerns Relating to Exposures  tc "3.2	Summary
of Toxicity Concerns Relating to Exposures " \l 2 

	Chlorine Dioxide/Sodium Chlorite - Report of the Hazard Identification
Assessment Review Committee and the Antimicrobials Division Toxicity
Endpoint Selection Committee (USEPA 2005a) indicates that there are
toxicological endpoints of concern for chlorine dioxide.  The endpoints
and associated uncertainty factors used in assessing the risks for
chlorine dioxide are presented in Table 3.2.  These endpoints have also
been identified for sodium chlorite.  Since the same endpoints have been
identified for both chemicals, this risk assessment examines products
causing the greater exposure if a similar use scenario is found for both
chlorine dioxide and sodium chlorite.  The reader is referred to USEPA
(2005a) for the derivation of the risk-based inhalation RfC values.

Table 3.2. Toxicological Endpoints Selected for Chlorine Dioxide (and
Representative of Sodium Chlorite).  SEQ CHAPTER \h \r 1 

Exposure

Scenario	Dose Used in Risk Assessment

(mg/kg/day) 	UF/ MOE for Risk Assessment	Study  and Toxicological
Effects

Acute Dietary	An acute dietary endpoint was not identified in the data
base for chlorine dioxide.



Chronic Dietary	

NOAEL =3 mg/kg/day

 	 UF = 100 

(10x inter-species extrapolation, 10x intra-species variation)

FPQA = 1

Chronic  PAD = 0.03 mg/kg/day	  SEQ CHAPTER \h \r 1 Developmental
Toxicity - Rat (Orme et al., 1985)- based on depression of serum T4
levels in pups from dosed maternal rats and delays in development of
locomotor and exploratory behavior activity at 14 mg/kg/day

Two-generation reproduction toxicity study (CMA, 1996) - decreases in
absolute brain and liver weight, and lowered auditory startle amplitude
at LOAEL of 6 mg/kg/day  



  SEQ CHAPTER \h \r 1 Incidental Oral

(short- and intermediate-term)	NOAEL =3 mg/kg/day	MOE = 100	See summary
for dietary assessment  



Dermal

(All Durationsa)

	NOAEL= 3 mg/kg/day

	 MOE = 100	See summary for dietary assessment  

[Assume 100% dermal absorption]



Inhalation

	 see ADTC endpoint selection document for explanation of NOAEL/LOAEL
values and effects (USEPA 2005a)	 Occupational ‘RfC’ = 0.009 mg/m3
(0.003 ppm)b

Homeowner short-term ‘RfC’ = 0.14 mg/m3 (0.05 ppm)b 	  SEQ CHAPTER
\h \r 1 Inhalation toxicity studies- Rat:

Homeowner short-term: Dalhamn, 1957 [LOAEL of 28 mg/m3 (10 ppm)]

Occupational exposure: Paulet and Debrousses, 1970, 1972 using  LOAEL of
1.0 ppm (2.8 mg/m3); Dalhamn, 1957 using  NOAEL of  0.1 ppm (0.28
mg/m3).  

	Homeowner long-term:

Agency RfC methodology used to derive a RfC value of 2 x 10-4 mg/m3 or
0.00007 ppm (USEPA, 2000)	(Paulet and Debrousses, 1970, 1972) selected
as co-critical studies (USEPA, 2005a)

aBased on the use of an oral endpoint for dermal risk assessments and
the lack of a dermal absorption study, a dermal absorption value of 100%
as default will be used.  Short-term is 1 to 30 days; Intermediate-term
is 1 to 6 months; and long-term is greater than 6 months.			

bunit conversion:  ppm = (mg/m3 x 24.45) / mw.  For chlorine dioxide 1
ppm = 2.8 mg/m3 

	3.3	FQPA Considerations  tc "3.3	FQPA Considerations " \l 2 

	

	  SEQ CHAPTER \h \r 1 The endpoint selected for both dietary and
non-dietary exposures was based upon adverse effects observed in
offspring from developmental and reproductive toxicity data.  Consistent
with the approach used by the EPA’s Office of Water for use of
chlorine dioxide as a drinking water disinfectant (Federal Register Vol.
63, No. 61, pages 15673-15692, March 31, 1998) and the updated guidance
on selection of a safety factor under FQPA, the endpoint selected for
assessment of risk from dietary and non-dietary exposure to chlorine
dioxide is felt  to be protective of potentially susceptible populations
including children, based upon the selection of an endpoint and effects
observed in offspring and the use of an NOAEL value based on those
effects.   Therefore it can be concluded that an additional safety
factor under FQPA is not necessary in this case for dietary and/or
residential risk assessments, and that the traditional uncertainty
factor (MOE) of 100 for intraspecies and interspecies variation will
support the safety standard of ‘reasonable certainty of no harm’ as
required by the FQPA statute for food-use pesticides (USEPA 2005).  

4.0	RESIDENTIAL AND PUBLIC ACCESS PREMISES tc "4.0	RESIDENTIAL AND
PUBLIC ACCESS PREMISES" 

Summary of Registered Uses  

	Chlorine dioxide and/or sodium chlorite products are used by homeowners
as disinfectants as well as to control mold and mildew.  For this
assessment, household cleaning products have been grouped together to be
represented by the higher application rate from the chlorine dioxide and
sodium chlorite products.  For example, EPA Reg. No. 9804-3 is
representative of products that are used in the home to clean floors,
bathroom surfaces, shower stalls, laundry rooms, and hampers.

	Sodium chlorite is also used for homeowner treatments of circulation
systems in swimming pools and spas.  The pool and spa product, EPA Reg.
No. 70060-20, is formulated as a solid tablet.  In addition, chlorine
dioxide has a registered use for HVAC systems.  Applications to
residential heating, ventilating, air-conditioning (HVAC) systems are
not generally performed by the homeowner, but rather a commercial
applicator (e.g., EPA Reg. No. 9804-1).  Therefore, homeowner-based HVAC
applications are not presented; only potential exposures during post
application activities.  Finally, there is a continuous release product
packaged as a sachet that releases chlorine dioxide as a gas over time
in homes, automobiles, etc.

	4.2	Residential Exposure/Risk Pathway  tc "4.4	Residential
Exposure/Risk Pathway " \l 2 

		4.2.1	Residential Handler Exposure  tc "4.4.1	Residential Handler
Exposure " \l 3 

	EPA has estimated both the potential dermal and inhalation routes of
exposure for residential handlers.  The dermal and inhalation exposures
are presented in separate sections below.

			4.2.1.1	Residential Handler Dermal Exposure and Risk  tc "4.4.1
Residential Handler Exposure " \l 3 

The following equations were used to calculate potential dermal doses
and risks to handlers:

Daily Exposure:	E = UE * AR * AT

Where:  

E	=	amount (mg ai/day) deposited on the surface of the skin that is
available for

		dermal absorption;

UE	 =	unit exposure value (mg ai/lb ai) derived from August 1998 PHED
data or from 

CMA data;

AR	=	normalized application rate based on a logical unit treatment, such
as acres, 

square feet, gallons, or cubic feet. Maximum values are generally used
(lb ai/A, lb 

ai/sq ft, lb ai/gal, lb ai/cu ft); and

AT 	=	normalized application area based on a logical unit treatment such
as acres 

(A/day), square feet (sq ft/day), gallons per day (gal/day), or cubic
feet (cu 

ft/day).

Daily Dose:	ADD = E * (ABS / BW)

Where:

ADD 	= 	absorbed dose received from exposure to a pesticide in a given
scenario; in the 	case of chlorine dioxide, the dermal absorption is
defaulted to 100% because of 	the lack of data. (mg pesticide active
ingredient/kg body weight/day);

E 	=	amount (mg ai/day) deposited on the surface of the skin that is
available for

dermal absorption;

ABS 	= 	a measure of the amount of chemical that crosses a biological
boundary such as

the skin (% of the total available absorbed); and

BW	= 	body weight determined to represent the population of interest in
a risk

assessment (kg).

Margins of Exposure:	MOE = (NOAEL or LOAEL) / ADD

Where:

MOE 			= 	margin of exposure, value used to represent risk;

NOAEL or LOAEL	= 	dose level in a toxicity study, where no observed
adverse effects 

(NOAEL) or where the lowest observed adverse effects (LOAEL)

occurred in the study; and

ADD 			= 	average daily dose or the absorbed dose received from exposure
to

a pesticide in a given scenario (mg pesticide active ingredient/kg

body weight/day).

A series of assumptions and exposure factors served as the basis for
completing the handler risk assessment for each use site category.  Each
general assumption and factor is detailed below. Assumptions specific to
the use site category are listed in each separate section below.  The
general assumptions and factors used in the risk calculations include:

Chlorine dioxide is a widely used disinfectant and has a large number
of use patterns.   As a result, AD has patterned this risk assessment on
a series of likely representative scenarios for each use site that are
believed by AD to represent the vast majority of chlorine dioxide uses.

The toxicological endpoint of concern for dermal risks is from a
reproductive study; therefore the average body weight of an adult female
handler (i.e., 60 kg) was used to complete the dermal risk assessment.

Exposure factors used to calculate daily exposures to handlers are based
on applicable data, if available.  For lack of appropriate data, values
from a scenario deemed similar enough by the assessor might be used. 

The maximum application rates allowed by the representative labels were
used in the development of the risk estimates (see Tables 2.1, 2.2, and
2.3). 

Those assumptions specific to the residential handler assessment are as
follows:

Unit Exposure Values:  Dermal unit exposure values were taken from the
proprietary Chemical Manufacturers Association (CMA) antimicrobial
exposure study (MRID 42587501) or from the Pesticide Handler Exposure
Database (PHED, 1998).  

For mopping, the CMA dermal unit exposure value for ungloved mopping
was used (71.6 mg/lb ai).  This value is based on data collected from
six replicates mopping floors and receiving exposure via contact with
the mop or with the bucket.

For trigger-pump sprays, the PHED dermal unit exposure value for
ungloved, short-pants, and short-sleeved clothing scenario for aerosol
spraying (220 mg/lb ai) was used as a surrogate for the trigger pump. 
This value is based on data collected from 30 dermal and 15 hand
replicates who applied the spray on surfaces (only 15 hand replicates
available because ½ the test subjects wore chemical resistant gloves).

For solid place (tablets), the CMA dermal unit exposure value for
placing solids, such as tablets, is 10.8 mg/lb ai (ungloved).  This
value is based on only one replicate.    The value for the dermal
exposure when wearing gloves is reduced to 0.142 mg/lb a.i.  This value
is also based on only one replicate (metal working fluid).Amount
handled/treated: The amounts handled/treated were estimated based on
information from various sources, including the Standard Operating
Procedures (SOPs) for Residential Exposure Assessments (2000).  In
certain cases, no standard values are available for some scenarios. 
Assumptions for these scenarios are based on AD estimates and could be
further refined from input from affected sectors.  The following
assumptions were made:

Trigger-pump sprayers: 0.5 liters or 0.13 gal/day

Mopping: 1 gal/event

Swimming pools:  20,000 gallons

	Two scenarios (mopping and spraying) were examined for residential
cleaning purposes in this risk assessment and one scenario for the
pool/spa application.  Table 4.1 provides the label information that is
representative of the high-end residential cleaning and pool/spa
treatment scenarios for chlorine dioxide as well as sodium chlorite. 
For use in residential cleaning, sodium chlorite was identified for the
high-end exposure.  Sodium chlorite has the only swimming pool and spa
use on the labels reviewed for this assessment.

Table 4.1. Exposure Scenarios Associated with Residential Exposure
Assessed in this Document

Representative Use	Application Method	EPA Registration Number 
Application Rate 

(lb ai/gal)	Exposure Scenario Assessed

Application to hard surfaces	mop

trigger-pump sprayer	9804-3

(chlorine dioxide)	0.002 lb ai/gal	Short-term Adult Handler (dermal and
inhalation)

Application to swimming pools and spas	place solid (tablets)	70060-20

(Sodium Chlorite)	2 tablets in skimmer and 2 tablets in hair/lint basket
to clean pool circulation system per 10,000 gallons of water. 100 g x 4
tablets x 20%ai = 80 g ai/10,000 gal = 

1.8E-5 lb ai/gallon 	Short-term Adult Handler (dermal and inhalation)



The results of the MOE analysis for these scenarios are presented in
Table 4.2.  Although the dermal endpoint represents short-,
intermediate-, and long-term durations, the exposure duration of most
homeowner applications of cleaning products and pools are believed to be
best represented by the short-term duration.  The toxicological endpoint
is based on an oral study and no dermal absorption value is available. 
Therefore 100% dermal absorption was assumed for chlorine dioxide and/or
chlorite ion residues.  The dermal MOEs for the general use on floors,
etc., are above the target MOE of 100, and therefore, are not of concern
(i.e., the short-term dermal MOEs for applications to hard surfaces are
3,200 for the trigger-pump sprayer and 1,300 for the mopping).  The
short-term dermal MOE for pool and/or spa treatments is 46 without the
use of gloves and the MOE is 500 with the use of gloves.

  

Table 4.2. Calculation of Short-term Dermal MOEs for Residential
Handlers

Exposure Scenario	Application Ratea

(lb ai/gal)	Amount Handled/ Treated Dailyb

(gal)	Baseline Dermal Unit Exposurec (mg/lb ai)	Baseline Dermal Dosed,e 

(mg/kg/day)	Baseline Dermal MOEf 

(Target MOE = 100)

Mopping

(CMA data)	hard surfaces	0.002	1	71.6	0.0024	1300

Trigger-pump sprayer (Aerosol can

PHED data used as surrogate)	hard surfaces	0.002	0.13	220	0.00095	3200

Solid Place 

(Tablets)

	Pools & Spa water circulation systems	1.8E-5

(4 tablets /10,000 gal.  of pool water.  Tablet is 100 g x 4 tablets x
20%ai = 80 g ai/10,000 gal = 1.8E-5 lb ai/gal)	20,000	10.8

(no gloves)	0.065

(no gloves)	46

(no gloves)





0.412

(gloves)	0.006

(gloves)	500

(gloves)



a	Application rates are the maximum application rates determined from
EPA registered labels for chlorine dioxide, sodium chlorite, and sodium
chlorate.

b	Amount handled/treated per day values are based on AD estimates.

c	Dermal unit exposures are from CMA and PHED. 

d	Baseline dermal:  Long-sleeve shirt, long pants, no gloves for mopping
and short-pants, short-sleeved shirt, and no gloves for spraying.

e	Dermal dose (mg/kg/day) = [unit exposure (mg/lb ai) * dermal
absorption (1.0) * appl. rate ( lb ai/gallon) * gallons handled / body
weight (60 kg).

f	MOE = NOAEL (mg/kg/day) / Daily Dose [Where short-and
intermediate-term dermal NOAEL = 3 mg/kg/day].  Target MOE is 100.

			4.2.1.2	Residential Handler Inhalation Exposure and Risk

	The potential inhalation of chlorine dioxide may occur from off gassing
during application of the aqueous solution.  Chlorine dioxide has the
potential to generate a gas during the residential uses of mopping and
spraying.  However, it is unlikely that levels of concern for chlorine
dioxide would be generated outdoors while treating swimming pools & spas
with tablets placed into water. 

	Of the three inhalation toxicological endpoints selected, the
short-term homeowner (i.e., not a continuous exposure) best represents
the inhalation exposure duration of residential handlers.  The
short-term residential RfC is 0.05 ppm.  

	To determine the potential inhalation handler exposure resulting from
the vapor of chlorine dioxide as a general purpose cleaner, the model
EFAST (Exposure and Fate Assessment Screening Tool) was used to estimate
the air concentration. OPPT/EETD has developed the model, EFAST, to
estimate air concentrations.  More information and access to the EFAST
model is available at   HYPERLINK
"http://www.epa.gov/opptintr/exposure/" 
http://www.epa.gov/opptintr/exposure/ .  In summary, EFAST Version 1.1
bases its air concentration estimates on physical/chemical properties. 
The air concentration estimates for the chlorine dioxide are based on
the model’s standard input parameters.  The following information is
presented in the EFAST model:

      “....it is assumed to contact the target surface, and to
subsequently volatilize at a rate that depends upon the chemical's
molecular weight and vapor pressure.”

The molecular weight of chlorine dioxide is 67.45 g/mol and the vapor
pressure is >760 mm Hg at 25 degrees C.  EFAST estimates a peak air
concentration as well as a daily air concentration.  The peak air
concentration estimate “... is the highest instantaneous air
concentration that is modeled during the exposure event.”  This peak
air concentration is instantaneous and at the source of the treatment
solution.  The peak concentration is not a useful measurement for
comparison to the inhalation RfC selected.

EFAST was used to model the air concentration from general purpose
cleaners using an application rate of 0.002 lb ai/gal (i.e., weight
fraction = 0.00024).  The peak instantaneous air concentration is 0.265
mg/m3  (0.09 ppm) and the average daily TWA air concentration is
determined to be 0.00794 mg/m3 (0.003 ppm).

	The inhalation endpoint (RfC) for one-time applications is 0.05 ppm. 
Based on the average daily air concentration (representing both
application and post application), the handler inhalation exposures of
chlorine dioxide are not of concern (i.e., the average air concentration
estimated by EFAST of 0.003 ppm is below the RfC of 0.05 ppm and the
peak concentration of 0.09 ppm is below the ACGIH STEL of 0.3 ppm).  

	

		4.2.2	Residential Post Application Exposure  tc "		4.4.2	Residential
Postapplication Exposure " \l 3 

	Typically, most products used in a residential setting result in
exposures occurring over short-term time duration (1 – 30 days).  If
the products are used on a routine basis (i.e., once a week) and the
active ingredient has a long indoor half-life, exposures may occur over
an intermediate-term time duration (30 days – 6 months).  However, AD
does not have residue dissipation data or reliable use pattern data
including the frequency and duration of use of antimicrobial products
used in the residential setting.  Therefore, even though AD does not
believe that the use patterns of many residential products result in
intermediate-term exposure, they are assessed to provide an upper bound
estimate of exposure (e.g., day care centers).  Note:  For chlorine
dioxide the dermal and oral endpoints and durations are identical. 

	For the purposes of this screening-level assessment, post application
scenarios have been developed that encompass multiple products, but
still represent a high-end scenario for all products represented.  Four
scenarios have been considered: (1) exposure to residue from hard floors
that have been cleaned with a solution containing chlorine dioxide, (2)
exposure to chlorine dioxide used to clean residential HVAC systems, (3)
exposure to a continuous release (gas) deodorizer, and (4) swimming. 

		4.2.2.1	Hard Surface/Floor  tc "4.4.2.1	Hard Surface/Floor " \l 4 

Dermal Exposure to Children from Treated Floors

Exposure Calculations

	There is the potential for dermal exposure to toddlers crawling on hard
floors after mopping with chlorine dioxide products and to carpets after
application with a formulated dust product.  The hard floor scenario was
selected because it represents the higher amount of residue transferred
(i.e., 5% residue transfer assumed for carpets and 10% for hard
surfaces).  Exposures and MOEs were calculated for children contacting
treated hard surface floors in residential homes (short-term exposure)
and in commercial daycare centers (intermediate-term exposure). To
determine toddler exposure to floor residues (mopping), the following
equation was used: 

PDD =  AR x DTF x DRF x CF1 x CF2 x SA

			BW			

where,

 	PDD	=	Potential daily dose;

AR	=	Application rate (lb/ft2);

DTF	=	Dermal transfer factor (fraction, unitless);

DRF	=	Disinfectant fraction remaining on floor (unitless);

CF1	=	Conversion factor (4.54x105 mg/lb);

CF2	=	Conversion factor (10.8 ft2/m2);

SA	=	Surface area of the body which is in contact with floor (m2); and

BW	=	Body weight (kg)

Assumptions

Toddlers (3 years old) were used to represent the 1 to 6 year old age
group.  A body surface area of 0.657 m2 and a body weight of 15 kg was
been assumed, which are the median values for 3 year olds (USEPA, 1997).

Generic household cleaners are commercially available in a large range
of concentrations.  It is assumed that one gallon of diluted treatment
solution is used to treat 1000 ft2 of floor.  The maximum application
rate on the chlorine dioxide and/or sodium chlorite product labels for
application to hard surfaces which are believed to encompass floors
where children may play was 0.002 lb ai/gal.  Therefore, the application
rate used in the post application scenarios was 0.000002 lb ai/ft2.  

No transferable residue data were available that could be used to
estimate the transfer of chlorine dioxide or chlorite ion from the floor
to skin.  Therefore, it is assumed that 10% of the deposition rate is
available for dermal transfer (USEPA, 2000, and 2001).  This is a very
conservative estimate for chlorine dioxide as it has a very high vapor
pressure and volatility will affect the amount of residue deposited.

No data could be found regarding the quantity of dilute treatment
solution left on the floor after treatment.  It has been assumed that
25% of the treatment solution remains on the floor after the final
mopping (i.e., some solution remains in the mop itself and some in the
bucket).

It was assumed that the exposed toddler plays regularly on the treated
floor.  In a residential home, short-term exposure duration is most
likely since homeowners are expected to clean the floor only
intermittently.  In a commercial daycare center, intermediate-term
exposure duration is likely since it is expected that the floors are
cleaned on a routine basis. 

Results

	The calculations of the short- and intermediate-term dermal doses and
MOEs are shown in Table 4.3.  The dermal MOEs for the residential
settings (short-term MOE) and institutional settings (intermediate-term
MOE) are identical because the endpoints and uncertainty factors are the
same for both durations.  The estimated dermal MOE of 280 is not of
concern (i.e., above the target MOE of 100).

 

Table 4.3.  Short- and Intermediate-term Post Application Dermal
Exposures and MOEs for Children Contacting Treated Floors



Exposure scenario	

Application rate 

(lb ai/sq ft)	

Product remaining after mopping	

Percent trans. residue	

Body area in contact with floor (m2)	

Potential daily dosea (mg/kg/day)	

Dermal MOEb



Hard surfaces - residential and daycare settings 	

2x10-6	

25%	

10%	

0.657	

0.017	

280



a 	Potential daily dose (mg/kg/day) = [(Application rate, lb
ai/ft2)*(conversion factor, 454 g/lb)*(conversion factor, 1,000 mg/g) *
(conversion factor, 1 ft2/0.093 m2) * (product remaining after mopping,
25%) * (dermal transfer factor, 10%) * (body surface area in contact
with floor, 0.657 m2)] / (body weight, 15 kg)

b	Dermal MOE = NOAEL (mg/kg/day) / Potential daily dose (mg/kg/day)
[Where short- and intermediate-term dermal NOAEL (derived from an oral
study and 100% dermal absorption is assumed) is 3 mg/kg/day.  Target MOE
= 100.

Child Incidental Ingestion Exposure to Treated Floors

Exposure Calculations

	In addition to dermal exposure, toddlers crawling on treated hard
floors will also be exposed to chlorine dioxide or chlorite ion residues
via incidental oral exposure through hand-to-mouth activity.  To
calculate incidental ingestion exposure to these chemicals due to
hand-to-mouth transfer, the methodologies established in the Standard
Operating Procedures (SOPs) for Residential Exposure Assessments (USEPA
2000 and 2001) were used.  These use assumptions are similar to those
used in calculating dermal exposures for toddlers crawling on treated
hard floors.  Because the incidental oral endpoints and uncertainty
factors are identical for short- and intermediate-term durations,
scenarios for children at day care centers are not listed separately. 
Exposures were calculated for children contacting treated floors in
residential homes using the following equations for hand-to-mouth
transfer of pesticide residues to toddlers:

PDD = SR x DTF x SA x EF x ET x SE x CF1				        

                                         BW

where:

PDD		=		Potential daily dose (mg/kg/day);

SR		=		Indoor surface residue (μg/cm2);

DTF		=		Dermal transfer factor (unitless fraction);

SA		=		Surface area of the hands that contact both the treated area, and
the individuals mouth (cm2/event);

EF		=		Frequency of hand-to-mouth events (events/hr); 

SE		=		Saliva extraction efficiency (unitless fraction); 

ET		=		Exposure time (4 hrs/day);

CF1		=		Unit conversion factor (0.001 mg/µg); and

BW		=		Body weight (15 kg)

And

SR=AR x DRF x CF2 x CF3								

where:

SR		=		Surface residue (µg/cm2);

AR		=		Application rate (lb ai/ft2);

DRF		=		Disinfection fraction remaining on floor (unitless);

CF2		=		Unit conversion factor (4.54x108 µg/lb); and

CF3		=		Unit conversion factor (1.08x10-3 ft2/cm2)

Assumptions 

Toddlers (3 years old) were used to represent the 1 to 6 year old age
group and are assumed to weigh 15 kg, the median for male and female
toddlers (USEPA, 2000 and 2001). 

Based on HED’s Residential SOP, it was assumed that the surface area
used for each hand-to-mouth event is 20 cm2.  For short-term exposures,
it is assumed that the frequency of hand-to-mouth events is 20 events
per hour (90th percentile) (USEPA 2001).  A separate assessment at the
intermediate-term duration is not necessary, as the short-term
assessment is more conservative because the frequency of hand-to-mouth
events for the intermediate-term exposure duration is less than the
short-term and because the toxicological endpoints and uncertainty
factors are the same for both durations.

The exposure time was 4 hours a day (USEPA, 2000 and 2001).

The saliva extraction efficiency was 50% (USEPA, 2000 and 2001).

The labels did not provide information on the volume of disinfectant to
be used for cleaning surfaces such as floors.  It was assumed that the
diluted treatment solution was applied at a rate of 1 gallon per 1,000
sq. ft. The maximum application rate on the product labels for
application to hard surfaces is 0.002 lb ai/gal (EPA Reg. No. 9804-3). 
Therefore, the application rate used in the post application scenario
was 0.000002 lb ai/ft2.  

No data could be found regarding the quantity of dilute treatment
solution left on the floor after treatment.  It has been assumed that
25% of the treatment solution remains on the floor after the final
mopping (i.e., some solution remains in the mop itself and some in the
bucket).

No transferable residue data were available that could be used to
estimate the transfer of chlorine dioxide and chlorite ion from the
floor to skin.  Therefore, it was assumed that 10% of the deposition
rate is available for dermal transfer (USEPA, 2000 and 2001).

Results

	The calculation of the short-term oral doses and the oral MOEs are
shown in Table 4.4.  The oral MOE is 2,300 and is above the target MOE
of 100.

	For the short-term exposures, it was necessary to determine the total
MOE since the toxicity effects are the same for the dermal and oral
routes.  The short-term total MOE for children contacting treated floors
(dermal + oral routes) is 250 which is greater than the target MOE of
100, and therefore is not of concern.  The total MOE was estimated using
the following equation: Total MOE = 1 / ((1/MOEdermal) + (1/MOEoral))
where, MOEdermal = 280 and MOEoral = 2,300.

Table 4.4.  ST Incidental Oral Post Application Exposures and MOEs for
Children Contacting Treated Floors

Exposure Scenario	

Appl. Rate

 (lb ai/

sq ft)	

Product Remaining after Mopping	

Surface Residuea (µg/cm2)	

Percent transferable residue	

Surface area mouthed (cm2/event) 	

Exposure Frequency (events/hr)	

Saliva Extraction Factor	

Exp. Time (hrs/day)	

Potential Daily Doseb (mg/kg/day)	

Oral MOEc 



Hard surfaces - residential setting	2x10-6	

25%	

0.245	

10%	

20	

20	

50%	

4	0.0013	

2,300 



a 	Surface residue (µg/cm2) = (application rate, lb
ai/ft2)*(disinfectant fraction remaining on floor, 0.25)*(conversion
factor to convert lb to µg, 4.54E+08 µg/lb)*(conversion factor to
convert ft2 to cm2, 1.08E-03 ft2/cm2)

b 	Potential daily dose (mg/kg/day) = [(surface residue,
µg/cm2)*(transferable residue, 0.10)*(exposure time, 4
hrs/day)*(surface area of hands, 20 cm2/event)*(frequency of
hand-to-mouth activity, 20 events/hr)*(extraction by saliva, 50
%)*(conversion factor to convert µg to mg, 0.001 mg/µg)]/ (body
weight, 15 kg)

c 	MOE = NOAEL (mg/kg/day) / potential daily dose (mg/kg/day) [Where
short-term oral NOAEL = 3 mg/kg/day].  Target MOE = 100.

Child Inhalation Exposure after the Treatment of Floors

	Chlorine dioxide can potentially be released into the air as a
gas/vapor after it is applied as an aqueous solution to hard surfaces
such as floors.  At this time there are no air concentration data
available to assess the release of chlorine dioxide during or after
mopping floors.  There are, however, air concentration measurements
available after the application of chlorine dioxide as a dust treatment
on carpets (Speronello 2005).  Although there are limitations to this
study (e.g., not conducted under Good Laboratory Practices (GLPs),
minimal information is available in the study report, and the study did
not monitor aqueous applications), it is the only data source available
at this time.  In addition, the results are directly applicable to the
carpet dust application of chlorine dioxide (e.g., EPA Reg. No.
58300-16).  Finally, a theoretical approach to estimating chlorine
dioxide air concentration is also presented below based on dilution and
ventilation equations.

Monitoring Data:

	Speronello (2005) measured chlorine dioxide air concentrations in a
10ft x 10ft x 8ft room.  Chlorine dioxide, formulated as Sanitizer 71
powder, was applied to a carpet at application rates of 0.5 gram/ft2,
1.5 gram/ft2, and 2.5 gram/ft2.  The limit of detection for the sampling
was 0.01 ppm.  Samples were collected at 1, 36, and 60 inches above the
carpet.  The room was reportedly ventilated at 35 and 135 cfm, however,
the study indicates that the configuration of the inlet/outlet exhaust
was such that minimal ventilation actually occurred.  One experiment per
application rate was monitored at the 135 cfm ventilation rate and it
appears that a similar sampling schedule was used for the experiments at
the 35 cfm ventilation rate.  Raw data tables were not provided but the
data were presented graphically.  It is unclear for what durations
samples were collected and time weighted averages (TWAs) were not
reported.  The results indicate that at the lower ventilation rate
(i.e., 35 cfm) the peak concentration of chlorine dioxide was measured
at 0.3 ppm for all application rates.  For the 135 cfm ventilation
experiment, peak air concentrations were measured as 0.1 ppm, 0.3 ppm,
and 0.5 ppm for the 0.5, 1.5, and 2.5 gram/ft2 rates, respectively.  Air
samples were nondetect (i.e., less then 0.01 ppm) after 3 to 4 hours.

To determine the inhalation risks associated with chlorine dioxide
vapors as a result of the carpet dust applications, the appropriate
exposure duration and frequency need to be compared to an inhalation
toxicity endpoint of similar duration and frequency.  Carpet and/or
mopping hard surface floor treatments are believed to be intermittent in
frequency.  Therefore, the short-term, single exposure inhalation
endpoint for residents, RfC of 0.05 ppm, is the appropriate endpoint to
use in this exposure scenario.  

The air concentration data available in this study are peak measurements
with the sampling time not reported.  The peak concentrations measured
in the first 3 or 4 hours after application (up to 0.5 ppm) exceed the
level of concern (i.e., RfC of 0.05 ppm) by an order of magnitude (and
also exceeds the ACGIH STEL of 0.3 ppm).  However, the peak air
concentrations for chlorine dioxide decrease below the level of concern
after 3 or 4 hours, most likely earlier.  Actual inhalation risk
concerns are indeterminate because the air concentrations in the room
available for children to breathe are only measured in the study as peak
concentrations which are not directly comparable to the time weighted
average (TWA) toxicity value.  These data do, however, indicate that
additional study information and/or a new study are warranted to provide
a reasonable certainty of no harm for children (or adults) in rooms
treated with chlorine dioxide.

Dilution Ventilation Approach:

	In the dilution and ventilation approach to determining air
concentrations in a room, the application rate from EPA Reg. No. 9804-3
is used (USEPA 2005c).  As a bounding estimate, it is conservatively
assumed that the concentration in the dilute cleaning solution is
immediately released as the initial air concentration in the room.  From
this initial air concentration, the ventilation rate of the room and the
half-life of chlorine dioxide in an aqueous solution are used to
estimate the air concentration in the room every 30 minutes.  The
results are a bounding estimate of the maximum air concentration in the
room.  Actual results will be lower as the initial concentration of
chlorine dioxide in the air would not be equal to that of what is in the
treatment solution.  Furthermore, the half-life of chlorine dioxide in
an aqueous solution was used (i.e., 30 minutes).  The half-life of
chlorine dioxide in air is expected to be much lower.  The half-life in
the aqueous solution was used because the gas would be released over
time in the room rather then immediately as assumed.  

	The initial concentration of chlorine dioxide in the aqueous solution
is 0.6 ppm derived from the application rate of EPA Reg. No. 9804.3. 
This product is mixed as a 0.1% ai solution of 24 oz of product per
gallon of water and it is assumed that 1 gallon of a treatment solution
is used to mop the floor which is equivalent to 681 mg chorine dioxide
(i.e., [8 lb/gal density x 0.001 ClO2 x 1 ga/128 fl oz] x 24 fl oz
product/gal x 1 gallon mopping solution = 0.0015 lb ai of treatment
solution or 681 mg ai.).  Assuming all of the 681 mg of chlorine dioxide
is released into a 1,800 ft2 house (volume = 1,800 ft2 x 8 ft ceiling =
14,400 ft3 or 408 m3) the air concentration would be 0.6 ppm (i.e., 681
mg ai/408 m3 = 1.7 mg/m3 or 0.6 ppm).  Note:  The area of a house was
used to estimate the volume of the house, not the total surface area of
the house mopped.

The dilution ventilation equation is as follows:

t = Vr/Q ln [Ci/C]  	

Where: t	= time required in minutes

	C	= concentration at time t

	Ci	= initial concentration of the disinfectant

	Vr	= volume of area/room in ft3

	Q 	= air flow into room, in ft3/min.

The above equation does not incorporate the chlorine dioxide half life
in air.  To account for the ½ life of chlorine dioxide (t0.50 ), the
assumption of first order decay (ln2/t0.5), and the air exchange
parameter (ACH) the following equation was used to estimate C:

				C =   Ci  x e (-t  x (ACH + (ln2/t0.5))	

Where:  ACH = Vr/Q 

ACH 	= number of air exchanges per hour

Vr	= volume of area/room in ft3

		Q 	= air flow into room, in ft3/hr

It is assumed that it takes longer for chlorine dioxide to breakdown
from aqueous solution than when it is in gaseous state. The most cited
literature for the half-life of chlorine dioxide from an aqueous
solution states it to be 30 minutes (Note:  half-life in air not
available). 

Table 4.5 summarizes the concentrations for chlorine dioxide for every
30 minutes.  The results indicate that for an assumed room ventilation
rate of 43.2 ft3/minute, the bounding estimate of chlorine dioxide in
the air is below the inhalation level of concern of 0.05 ppm at 1.5
hours after treatment.  Based on this conservative bounding estimate,
the inhalation of chlorine dioxide during off gassing from the treatment
solution used to mop floors does not appear to be a risk of concern if
there is no reentry into a treated area during the first hour after
treatment (i.e., 1-hr REI).  To accurately determine the initial
concentration of chlorine dioxide in the air after mopping, air
monitoring data would be needed.

Table 4.5  Bounding Estimate of Chlorine Dioxide over Time (Mopping).

Time (minutes)	Time (hours)	Chlorine Dioxide (ppm)

0	0	0.6

30	0.5	0.27

60	1	0.13

90	1.5	0.057

120	2	0.026

180	3	0.0055

240	4	0.0011

300	5	0.0002

360	6	0.00005

420	7	0.00001

480	8	0.000002

540	9	0.0000005

8-hour TWA starting 0-hrs after treatment	0.08

8-hour TWA starting 1-hr after treatment	0.02



			4.2.2.2	Heating Ventilating and Air-Conditioning (HVAC) Systems  tc
"4.4.2.2	Ventilation Systems " \l 4 

There is one product registered for use in cleaning HVAC systems.  This
product, OXINE (EPA Reg. No. 9804-1), is a registered sanitizer for
residential/commercial/institutional HVAC systems.  It is formulated at
2 percent chlorine dioxide.  Label use directions indicate that the
product is mixed at a rate of 3.24 fluid ounces product per gallon of
water with an activator to activate the chlorine dioxide (500 ppm ClO2).
 The aqueous chlorine dioxide solution is then sprayed or fogged into
closed and sealed duct work.  After application, the label directions
indicate that the “…area should be opened and aired for one (1) hour
before repopulating.”   It is assumed that dermal post application
exposures are negligible for applications to HVAC systems.  This
assumption is supported by the deposition samples discussed below (BCI
2002).  However, it is assumed that post application inhalation exposure
can occur when people reenter a building after application.  

BCI (2002) monitored a chlorine dioxide treatment of a HVAC system in a
2250 ft2 residence.  The application was performed at the maximum
labeled rate (i.e., aqueous solution of 500 ppm).  The ambient air in
the house was monitored for chlorine dioxide gas during and after the
application.  Deposition of the chlorite ion was measured using 1 ft2
glass plates on the floor of each room.  Results of the study indicated
that the deposition samples were all nondetect (LOD not reported).  The
air concentrations monitored indicated a maximum instantaneous reading
of 0.02 ppm and the average of the readings was below the detection
limit of 0.01 ppm.

The short-term inhalation RfC for chlorine dioxide is 0.05 ppm. 
According to the label, the frequency of HVAC system treatments is to
“treat as required”.  The frequency of residential (and/or
commercial/intuitional) HVAC treatments is expected to be minimal (one
treatment per year may be an overestimate).  In addition, the half-life
of chlorine dioxide is rapid.  Therefore, inhalation exposure is
expected to be limited to short-term durations.  The maximum value
monitored by BCI (2002) during application and/or reentry was 0.02 ppm,
below the RfC value of 0.05 ppm.  Therefore, there are no inhalation
risks of concern.

			4.2.2.3	Continuous Release (Gas) Deodorizer tc "4.4.2.2	Ventilation
Systems " \l 4 

Product Use in Homes:

One product has been identified that is registered as a continuous
release of chlorine dioxide gas in homes (EPA Reg. No. 70060-12).  The
product is packaged as a pouch or sachet.  The product states that it
“…controls odor-causing bacteria, mold and mildew and chemical odors
in confined spaces…” and is for use in households, hospitals, and
institutions.  The product is packaged in 5, 10, 20, 50, 100, and 200
gram pouches/sachets.  Household uses include refrigerators, shoes,
closets, laundry hampers, cupboards, cabinets, drawers, diaper pails,
pet areas, and basements.  Other use sites of this product outside the
home include gym lockers, automobiles, boat cabins, and trash cans.

No monitoring data are available to determine the air concentrations in
the home.  Therefore, a bounding estimate of air concentration is
presented based on the application rate and the label-referenced
longevity of the pouches/sachets.  According to the label, the basement
rate is 200 grams of product per 500 ft2 of basement area for up to 2
months of treatment.  A 500 ft2 basement area is assumed to be
equivalent to a volume of 4,000 ft3 or 113 m3 (i.e., 500 ft2 x 8 ft
ceiling).  A linear release of the chlorine dioxide gas is assumed. 
Based on the rapid half-life of chlorine dioxide (~30 minutes for
aqueous solution and reportedly shorter in air), it is assumed that a
gas build up will not occur.  The theoretical constant air concentration
would be 0.52 ppm assuming no air exchange and no build up of chlorine
dioxide over time because of the short half-life (i.e., label rate of
200 grams of 5% ai product/500ft2 for 2 months, assuming an 8 ft
ceiling).  The RfC for long-term continuous exposure is 0.00007 ppm. 
Therefore, the theoretical concentration from the product’s release is
of concern.  This bounding estimate of exposure can be refined by
determining residential ventilation rates, identifying sensitive
analytical detection methods (current sampling techniques do not have
the capability of monitoring to a level of 0.00007 ppm), collecting
monitoring data, and determining the number of hours an individual is
exposed in treatment areas.  However, before any refinements to these
air concentration estimates are attempted, it should be determined if
the product’s efficacy can be maintained at the RfC of ~0.00007 ppm.

Product Use in Automobiles:

There are data available to assess the use of the continuous release
deodorizer product in automobiles (e.g., EPA Reg. No. 70060-12).  Two
studies were submitted that measured chlorine dioxide air concentrations
in automobiles (Wood and Gallo 1997, and Speronello 1998).  

Wood and Gallo (1997) measured chlorine dioxide in a total of 16
automobiles (8 cars parked outside and 8 cars parked inside a garage). 
Cars were parked in inside and outside parking lots to account for
sunlight degradation of chlorine dioxide.  The study author indicated
that “…approximately half the chlorine dioxide released was consumed
by sunlight”.  Cars parked outside were treated with 5, 15, 25, and 50
gram sachets while cars parked inside were treated with 5 and 25 gram
sachets.   An Interscan Digital Chlorine Dioxide Analyzer was used to
measure chlorine dioxide inside the cars (LOD appears to be 0.01 ppm). 
To sample chlorine dioxide in the cars, tubes were inserted through the
weather stripping of the doors to preclude dilution by opening the
doors.  Each car was sampled from 1 to 4 days.  Samples were taken for
some cars at 2, 4, 8, and 24 hours after placement of sachets and other
cars at 24, 27, 29, 33, and 50 hours after placement of sachets and
finally, some at 1, 2, 4, 8, 48, and 96 hours after placement of
sachets.  Duplicate and triplicate readings were recorded at each
sampling interval at various locations in the cars (i.e., floor, bench,
or face for a total of 2 or 3 samples per interval).  It appears that
reported air concentrations represent instantaneous measurements.  

The maximum reported single reading for outdoor cars was 0.19 ppm for
the 50 gram sachet and also 0.19 ppm for the indoor car with a 25 gram
sachet.  The maximum and average readings for all sampling intervals are
reported in Table 4.6.  Although some of the maximum single reading
values of chlorine dioxide exceed the short-term residential inhalation
toxicity of concern (i.e., level of concern is a RfC of 0.05 ppm), these
maximum single readings are not meaningful to determine risk concerns
when compared to the short-term inhalation RfC selected in this
document.  It is more appropriate to compare the peak measurements to
the ACGIH STEL which is based on a 15-minute average.  The highest
maximum single reading of 0.19 ppm from this study does not exceed the
STEL of 0.3 ppm.  The average of all of the instantaneous readings is
below the RfC and the STEL.  In conclusion, the data presented by Wood
and Gallo (1997) indicate that the concentration of chlorine dioxide
remains below the STEL and the average of the single measurements does
not exceed the RfC of 0.05 ppm. However, a more appropriate measurement
would have been to sample over a period of time that is representative
of the duration people spend in cars to obtain a time weighted average
(TWA). 

Table 4.6.  Maximum and Average Chlorine Dioxide Measurements in
Automobiles.

Chlorine Dioxide Reading (ppm)	Weight of Chlorine Dioxide Sachets

	5 grams	15 grams	25 grams	50 grams

Cars Parked Outdoors

Maximum single reading	0.01	0.06	0.1	0.19

Average of all readings	0.0005	0.009	0.011	0.029

Cars Parked Indoors

Maximum single reading	0.008	Not Sampled	0.19	Not Sampled

Average of all readings	0.002

0.008

	LOD = 0.01 ppm.

“Average of all readings” represents the average where nondetects
are counted as zero.

Speronello (1998) provided limited additional information on chlorine
dioxide measurements inside of automobiles.  Two cars using different
application rates were monitored in this study (problems were
encountered with the 3rd car and this experiment was discontinued).  One
car was treated with a 20 gram sachet and the other car was treated with
three 20 gram sachets.  Air concentrations in this study were measured
with an INTERSCAN Digital Compact Portable Analyzer (model 4335DG). 
This device recorded chlorine dioxide measurements at 10 second
intervals for 5 minutes.  Sampling intervals were 0, 1, 2, 4, 6, 8, 24,
101, 149, and 192 hours after initial placement of the sachet.  All of
the 5 minute samples in the car treated with 20 grams of chlorine
dioxide are below the detection limit of 0.05 ppm.  The results from the
car with the exaggerated application rate indicated a maximum chlorine
dioxide concentration of 0.091 ppm.  However, the text did not indicate
if this was a 5 minute sample or peak 10 second interval within the 5
minute measurement.  It also appears that some of the data tables in
Speronello (1998) are missing from the experiment identified as “Run
3”.  The data table for “Run 3” only includes the 10 second
measurements for the 0 hours after treatment interval.  The results of
this second study do not raise any additional concerns for peak
measurements, however, the data are of limited use to determine a TWA
concentration over the time period people spend in cars.

			4.2.2.4	 Swimming Pools & Spas

Sodium chlorite is used to treat circulation systems in swimming pools &
spas (EPA Reg. No. 70060-20).  The use directions for treating the
circulation systems include the following types of statements:

Do not add this product through any automatic dispensing device;

Apply product when no persons are in the pool;

For pools leave pump off for 6 to 12 hours before resuming pumping and
then wait at least 8 hours before allowing swimmers to enter pool;

Frequency of application is once every 3 – 4 weeks for pools and once
every 4 – 6 weeks for spas; and

For spas wait approximately 30 minutes before reusing spa.

Based on the intended use of the product, swimming in pools or spas
treated with chlorine dioxide is not assessed quantitatively.  When use
directions are properly followed, dermal, incidental oral, and
inhalation exposures to chlorine dioxide residual levels after the
cleaning of the circulation systems are expected to be minimal.

		4.2.3	Data Limitations/Uncertainties  tc "4.4.3	Data
Limitations/Uncertainties " \l 3 

	There are several data limitations and uncertainties associated with
the residential handler and post application exposure assessments. 
These include:

The exposure factors used to calculate daily exposures to handlers are
based on applicable data, if available.  For lack of appropriate data,
values from a scenario deemed similar enough by the assessor were used. 

Surrogate dermal unit exposure values were taken from the proprietary
Chemical Manufacturers Association (CMA) antimicrobial exposure study
(MRID 42587501) or from the Pesticide Handler Exposure Database (PHED,
1998).  See Appendix A for summaries of these data sources. 

The amounts handled/treated were estimated based on information from
various sources, including the Draft Standard Operating Procedures
(SOPs) for Residential Exposure Assessments (2000) and the Draft SOPs
for Occupational Exposure Assessments (2003).  In certain cases, no
standard values were available for some scenarios.  Assumptions for
these scenarios were based on AD estimates and could be further refined
from input from affected sectors. 

The full study report for the HVAC monitoring (BCI 2002) needs to be
submitted.

The two studies submitted to support the use in automobiles appear to
provide instantaneous readings of chlorine dioxide levels rather than
TWA. 

5.0	RESIDENTIAL AGGREGATE RISK ASSESSMENTS AND RISK CHARACTERIZATION tc
"5.0	RESIDENTIAL AGGREGATE RISK ASSESSMENTS AND RISK CHARACTERIZATION" 

	The aggregate risk assessment will be conducted in the overall risk
assessment for chlorine dioxide.  The non-dietary uses that may co-occur
for consideration in the aggregate assessment include the dermal and
incidental oral post application exposures to children playing on
treated floors and handler dermal exposures for adults.  

6.0	OCCUPATIONAL EXPOSURE AND RISK tc "6.0	OCCUPATIONAL EXPOSURE AND
RISK" 

	6.1	Occupational Handlers  tc "6.1 Occupational Handlers " \l 2 

		6.1.1	Dermal Handler Exposures

	

	Potential occupational handler exposure can occur in various use sites,
including agricultural premises, food handling, commercial and
institutional premises, medical premises, human drinking water systems,
industrial processes and water systems, application to material
preservatives, and swimming pools and other aquatic areas.  Table 6.1
provides the representative use scenarios that were assessed in this
risk assessment.

Table 6.1. Exposure Scenarios Associated with Occupational Exposure
Assessed in this Document

Representative Use	Application Method	EPA Registration Number (chemical
associated with use)	Application Rate (lb ai/gal)	Exposure Scenario
Assessed

Use Site Category I (Agricultural Premises and Equipment)a

Application to hard surfaces and equipment	low-pressure hand wand
74602-2 

(Sodium Chlorite)	(Application rate from label, 2.5 fl oz/gal)*(1
gal/128 oz)*(0.75 lb ai/gal) = 0.015	Short- and Intermediate-term (ST
and IT) Adult Handler (dermal and inhalation) and Adult Bystander and
Post Application (dermal and inhalation)



	trigger-pump sprayer

fogger (1 hour REI after fogging)	74602-2 

(Sodium Chlorite)	(Application rate from label, 2.5 fl oz/gal)*(1
gal/128 oz)*(0.75 lb ai/gal) = 0.015



mop	9150-2

(Chlorine Dioxide)	(Application rate from label, 3.25 fl oz/gal)*(1
gal/128 oz)*(0.69 lb ai/gal) = 0.018



foaming wand	9150-11

(Chlorine Dioxide)	0.72% ai product x 8.4 lb product density = 0.06 lb
ai/gal.  Label rate of 0.5 gal treatment solution (interior/exterior)
per truck sprayed using a foam wand capable of foaming 4 to 6 gallons of
foam per minute.



ULV fogger (e.g., Dramm fogger)	74602-2

(Sodium Chlorite)	( Egg house label rate, 1 gal product x 5% ClO2) per
50 gal = 0.0083)

	Use Site Categories II (Food Handling), III (Commercial/Institutional),
and V (Medical)

Application to hard surfaces and equipment without food contact

	mop 	9150-10 active

(10589-3 transferred)

(Chlorine Dioxide)	(Application rate from label, 5 oz/gal)*(1 gal/128
oz)*(0.49 lb ai/gal) = 0.019	ST/IT Adult Handler (dermal and inhalation)
and Adult Post Application/Bystander (dermal and inhalation)

	trigger-pump sprayer	21164-3

(Sodium Chlorite)

	(Application rate from label, 12 fl oz/gal)*(1 gal/128 oz)*(0.86 lb
ai/gal) = 0.08

	Application to foods (Fruit/vegetable rinse) 	dip	74602-2

(Sodium Chlorite)	(Application rate from label, 1.9 oz/gal)*(1 gal/128
oz)*(0.75 lb ai/gal) = 0.011

	Use Site Category VI (Human Drinking Water Systems)

Application to water systems (Water Treatment and water storage systems)
metering pump	9804-1

(Chlorine Dioxide)

	(Application rate from label, 3.25 fl oz/gal)*(1 gal/128 oz)*(0.27 lb
ai/gal) = 0.007	ST/IT Adult Handler; Potential for inhalation exposure
unknown at this time.

Use Site Category VII (Material Preservatives)

Applications to MWFs	liquid pour	9150-2

(Chlorine Dioxide)	batch method: 0.0001 

(per week)

continuous method: 

8E-7 (per day)

badly contaminated systems:  4E-6 (slug dose)	ST/IT Adult Handler
(dermal and inhalation) and Long-term Dermal and Inhalation for
Machinists.

Use Site Category VIII (Industrial Processes and Water Systems)

Application to pulp and paper white water systems	metering pump	74602-3

(Sodium Chlorite)

	(Application rate from label, 15 gal/100,000 gal white water to be
treated or 4 gal/100 tons paper produced)*(0.86 lb ai/gal) = 0.0001 lb
ai/gal white water or 3.44 lb ai/100 ton paper produced	ST/IT Adult
Handler (dermal and inhalation) and Adult Bystander (inhalation)

Application to oil systems (oil wells during secondary recovery
operations)	liquid pour	9150-2

(Chlorine Dioxide)

	(Application rate from label, 1 gal/10 gal)*(0.69 lb ai/gal) = 0.069.

Label indicates to portion 1 part of this solution to 150 parts
reinjection water.	ST/IT Adult Handler (dermal and inhalation) and Adult
Bystander (inhalation)

Use Site Category XI (Swimming Pools)

Application to public swimming pool circulation water systems (Swimming
pools)	solid place (tablets)	70060-20

(Sodium chlorite)

	4 tablet /10,000 gal 

(Pool tablet is 100 g x 4 tablets x 20%ai = 80 g ai/10,000 gal = 1.8E-5
lb ai/gal)	Short-term Adult Handler (dermal and inhalation)

Use Site Category XII ( Aquatic Areas)

Non-potable water systems (e.g., retention basins and ponds, decorative
pools and fountains)	liquid pour	9150-11

(Chlorine Dioxide)	0.00001

(18 fl oz x 0.72% ai per 100 gallons water)	ST/IT Adult Handler (dermal
and inhalation)

Use Site Category XIII (HVAC)

Application to ventilation systems

(HVAC)	airless sprayer

fogger  (1hour REI after fogging)	9804-1

(Chlorine Dioxide)	(Application rate from label, 3.25 fl oz/gal)*(1
gal/128 oz)*(0.27 lb ai/gal) = 0.007	ST/IT Adult Handler (dermal and
inhalation) and Short-term Child and Adult Post Application (inhalation)



	The following assumptions and unit exposure values were used in the
risk assessment:

Unit Exposure Values:  Dermal unit exposure values were taken from the
proprietary Chemical Manufacturers Association (CMA) antimicrobial
exposure study (MRID 42587501) or from the Pesticide Handler Exposure
Database (PHED, 1998).  

For low pressure hand wand, the CMA dermal unit exposure value for
ungloved use of a low pressure spray was used (191 mg/lb ai).  This
value is based on data collected from eight replicates that hand sprayed
carpet using 200 psi, and then used a push broom rake to raise the
carpet nap.  The time required to perform this activity took between 33
to 141 minutes.

For fogging, it is assumed that most of the exposure to the handler will
be due to preparing the fogger and that the handler leaves the room
immediately after fogging commences.  Therefore, the CMA dermal unit
exposure value for ungloved pouring was used (50.3 mg/lb ai).  This
value is based on data collected from one replicate that transferred the
pesticide from a large container to a smaller measuring or pouring
container.  The time required to perform this activity took between 5 to
78 minutes.

For mopping, the CMA dermal unit exposure value for ungloved mopping was
used (71.6 mg/lb ai).  This value is based on data collected from six
replicates mopping floors and receiving exposure via contact with the
mop or with the bucket.

For airless sprayer, PHED dermal unit exposure values for ungloved (38
mg/lb ai) and gloved (14.3 mg/lb ai) were used.  These values are based
on data collected from 15 replicates who applied a house stain to the
outside of a house.  The airless sprayer was used to represent the
spraying of HVAC duct work.  In addition to airless sprayers, duct work
applications would include ULV foggers, robotic spraying systems, and
various electric sprayers. 

For foam applicator, no data are available for foam applications.  PHED
dermal unit exposure values for an airless sprayer ungloved (38 mg/lb
ai) and gloved (14.3 mg/lb ai) were used.  These values are based on
data collected from 15 replicates who applied a house stain to the
outside of a house.  The airless sprayer was used to represent the
spraying of foam with a handwand treating trucks.  

For metering pump into human drinking water systems and industrial
processes and water systems, the unit exposure value from the CMA dermal
unit exposure value for gloved metering pump of a preservative is used
(0.00629 mg/lb ai).  This value is based on data collected from two
replicates.

For liquid pour, the CMA preservative dermal unit exposure value for a
gloved worker was used.  The dermal unit exposure is 0.135 mg/lb a.i.
and is based on 2 replicates.   SEQ CHAPTER \h \r 1 Although this unit
exposure is based on minimal replicates, the exposure value is similar
to the one found in PHED for a similar scenarios

For place solid (tablets) into public swimming pool water circulation
systems, the unit exposure value from the CMA dermal unit exposure for
ungloved use is 10.8 mg/lb ai and 0.412 mg/lb ai for gloved use, only
one replicate of each.   

For trigger-pump sprays, the PHED dermal unit exposure value for the
aerosol sprays were also used as a surrogate for the trigger pump.  The
PHED dermal unit exposure values for ungloved (190 mg/lb ai) and gloved
(81 mg/lb ai) were used.  These values are based on data collected from
15 replicates in which the aerosol spray was applied on surfaces.

Amount handled/treated:  The amounts handled/treated were calculated
based on AD estimates and could be further refined with input from
affected sectors.  The following assumptions were made:

Low-pressure hand wand: 2 gal/day

Trigger-pump sprayers: 1 liter/day (0.26 gal/day)

Airless sprayer for the HVAC use is assumed to be 5 gallons for one
worker.  This value is assumed to be representative of either a
commercial applicator treating multiple residential homes or a work day
treating a commercial building (5 gal)

Mopping:  it was assumed that two gallons of solution are used in the
food handling and commercial/institutional/industrial setting and 45
gallons are used in the medical setting.  The reason for this assumption
specific to medical premises is because in hospitals, a janitor cleans
approximately 28 rooms a day and must change the cleaning water every
three rooms (Helwig 2003)

Fogger (e.g., HVAC): 1 quart assumed for a single work day (0.25 gal)

Foam:	for application to animal transport vehicles, assume 1 truck
treated per hour x 8 hours per day.

Water storage systems: 34,000 gal/day (estimated storage capacity of 
water system for 100 people; based on Occupational SOPs, 	assumption of
170,000 gal/day for population of <500 people)

Pulp and Paper process water: 500 tons/day

Oil systems (oil wells): The following use was used to estimate the
amount of ai handled per day during oil-well activities.  Biocide is
typically added directly to drilling rig mud tanks via open pouring.
Over a 3 to 6 week period, while a 13,000 ft well is being drilled, 1 to
2 drums (1 drum = 42 gallons) of biocide may be used if microbiological
problems are encountered.  Therefore, the short-term exposure assessment
used 5.6 gallons for the amount of biocide handled per day by the
drilling rig worker [i.e., (2 drums x 42 gal/drum) / (5 days/week x 3
weeks) = 5.6 gal/day].  The intermediate-term exposure assessment used
2.8 gallons for the amount of biocide handled per day by the drilling
rig worker [i.e., (2 drums x 42 gal/drum) / (5 days/week x 6 weeks) =
2.8 gal/day].   SEQ CHAPTER \h \r 1  However, since the volume of water
being treated in secondary recovery operations is so large (i.e., 1,000
barrels per day, 42 gal/barrel, closed metering system), the available
CMA data can not be reliably extrapolated because they are based on
activities that handle much lower volumes and possibly different
techniques.  Therefore, it was assumed that if the open pour handling
activities for the other oil well operations resulted in MOEs that are
not of concern, then the MOEs for the closed system chemical metering
into secondary recovery operations would also be not of concern.  AD
requests that confirmatory data be conducted to show that this is
accurate.

Retention ponds/fountains: 10,000 gallons

Public swimming pool: 200,000 gallons



To calculate the dermal exposure for a worker treating fruits and
vegetables, the Consumer Exposure Pathway of the Exposure and Fate
Assessment Tool (CEM/E-FAST) was used.  CEM calculates conservative
estimates of inhalation and dermal exposures to consumer products.
Because CEM does not include a scenario similar to treating fruits and
vegetables via dip/rinse, a new user-defined scenario was created (using
the category “products that contact skin directly (dermal), potential
dose”). Surrogate exposure factor values have been extracted from
E-FAST defaults provided in the CEM help manual.  Assumptions and input
values for the model are listed in Table 6.3. 

	The calculated dermal MOEs are shown in Table 6.2.  Table 6.3 provides
the CEM model inputs and results for the fruit and vegetable rinse
scenario.  Calculated dermal MOEs less than the target MOE of 100 were
found for the following scenarios:

Agricultural Premises and Equipment

application to hard surfaces via low pressure hand wand (MOE = 31)

application to hard surfaces via mopping (MOE = 70)

foam applicator to animal transport vehicles/tractor trailer (MOE = 52)

Food Handling, Commercial/Institutional, and Medical Premises and
Equipment

application to hard surfaces via mopping (MOE = 66 for commercial and 3
for medical)

	In addition to the above handler assessments, the dermal exposure to
machinists contacting chlorine dioxide when used as a material
preservative in metal working fluid (MWF) is presented below.  There is
a potential for dermal and inhalation exposure when a worker handles
treated metalworking fluids.  Because of the high vapor pressure of
chlorine dioxide, the inhalation route of exposure is not assessed in
the typical manner (i.e., using the OSHA PEL for oil mist x percent
concentration in solution).  See Sections 6.1.2 and 6.2 for discussion
of the inhalation route.  

	The dermal route of exposure to machinists occurs after the chemical
has been incorporated into the metalworking fluid and a machinist is
using/handling this treated end-product.  Short-, intermediate-, and
long-term exposure estimates were derived using the 2-hand immersion
model from ChemSTEER.  The model is available at   HYPERLINK
"http://www.epa.gov/opptintr/exposure/docs/chemsteer.htm" 
www.epa.gov/opptintr/exposure/docs/chemsteer.htm .  The 2-hand immersion
equation is as follows: 

PDR = SA x % a.i. x FT x FQ

	       BW			

where: 

PDR	=	Potential dose rate (mg/kg/day);

SA		=	Surface area of both hands (cm2);

% a.i.	=	Fraction active ingredient in treated metalworking fluid
(unitless)

FT		=	Film thickness of metal fluid on hands (mg/cm2)

FQ		=	Frequency of events (event/day); 

BW	=	Body weight (kg)

Assumptions

The surface of area of both hands is 840 cm2 (US EPA 1997)

The body weight of an adult female is 60 kg (US EPA 1997)

The percent active ingredient in treated metalworking fluid for
continuous operations (label specified “continuous” rate selected
because this is a long-term duration) is 8E-7 lb ai/gallon or 0.00001 %
(EPA Registration No. 9150-2).  Three rates are listed on the
product’s label which contains 5% chlorine dioxide:  (1) Batch Method
is 32 fl oz product/1,000 gallons water-based cutting oils; (2)
Continuous Method is 2 gallons product/1,000,000 gallons water-based
cutting oils (2 gal x 8 lb/gal x 0.05 ai / 1,000,000 gallons cutting oil
= 8E-7 lb ai/gal); and (3) Badly Contaminated Systems is 10 gallons
product/1,000,000 gallons water-based cutting oils.  [To convert to % ai
= 8E-7 lbai/gal x 454 g/ 1 L x 1000 mg / 1 g x 1 gal/ 3.79 L = 0.1 mg/L
/ 10,000 = 0.00001% ai]

For short-, intermediate- and long-term durations, the film thickness on
the hands is 1.75 mg/cm2, which was extracted from the document
entitled, “A Laboratory Method to Determine the Retention of Liquids
on the Surface of Hands.” The film thickness is based on a machinist
immersing both hands in metalworking fluid and then partially cleaning
hands with a rag. The film thickness was chosen because the dermal
endpoint for short-, intermediate- and long-term durations is based on
systemic effects (USEPA, 1991).

	The results of the dermal exposure/risk to machinists working with
fluids treated with chlorine dioxide and/or sodium chlorite are
presented in Table 6.4.  The short-, intermediate-, and long-term dermal
MOE is 14,000, and therefore, not of concern.Table 6.2.  Short- and
Intermediate-Term Dermal and Inhalation Exposures/Risks to Occupational
Handlers from the Use of Chlorine Dioxide

Exposure Scenario	Application Ratea 

(lb ai/gal)	Area Treated Dailyb 

(gal)	Dermal Unit Exposuresc (mg/lb ai)	Baseline Attired	PPE (with
gloves)e



	Baseline	PPE-with gloves	Dermal Dosef (mg/kg/

day)	Dermal MOEg	Dermal Dosef (mg/kg/

day)	Dermal MOEg

Agricultural Premises and Equipment

Low Pressure Hand Wand (CMA-disinfectant)	hard surfaces	0.015	2	191	NA
0.096	31	No Data	No Data

Liquid Pour (CMA Data for cooling tower) -- fogger scenario	hard
surfaces	0.015	0.188	50.3	10.1	0.0024	1,300	0.00047	6,300

Trigger-pump Sprayer (PHED data for aerosol can used as surrogate)	hard
surfaces	0.015	0.26	190	81	0.012	240	0.0053	570

Mopping (CMA data)	hard surfaces	0.018	2	71.6	NA	0.043	70	No Data	No
Data

Foam Wand Applicator (using PHED airless sprayer)	animal transport
vehicles	0.06	0.5 ga/truck x 8 trucks/day = 4 gallons	38	14.3	0.15	20
0.057	52

Food Handling, Commercial/Institutional, and Medical Premises and
Equipment

Mopping (CMA data)	hard surfaces	0.019	2	71.6	NA	0.045	66	No Data	No
Data



	45

	1.0	3



Trigger-pump Sprayer (PHED data for aerosol can is used as surrogate)
hard surfaces	0.08	0.26	190	81	0.066	46	0.028	110

Human Drinking Water Systems

Metering Pump

(CMA)	water and storage systems	0.007	34000	NA	0.00629	No Data	No Data
0.025	120

Material Preservatives

Liquid Pour

(CMA)	MWF	0.0001 (Batch Method)	300	NA	0.184	No Data	No Data	0.000092
33,000

Industrial Processes and Water Systems

Metering Pump

(CMA data for pulp & paper)	paper and pulp white water systems	0.0344 lb
ai/ton paper	500 tons paper	NA	0.00454	No Data	No Data	0.0013	2,300

Liquid Pour

(CMA data for preservative)	oil systems	0.069	2.8	NA	0.135	No Data	No
Data	0.00043	6,900



	5.6



	0.00087	3,500

Swimming Pools and Aquatic Areas

Liquid Pour 

(CMA data)	retention ponds/fountain	0.00001	10,000	NA	0.135	No Data	No
Data	0.0045	670

Solid Place

 (CMA)	public pools	1.8E-5	200,000	10.8	0.412	0.65	5	0.025	120

HVAC Systems

Airless Sprayer 

(PHED data)	HVAC	0.007	5	38	14.3	0.022	140	0.0083	360

Liquid Pour 

(CMA data) -- fogger scenario	HVAC	0.007	0.25	50.3	10.1	0.0015	2,000
0.00029	10,000

a	Application rates are the maximum application rates determined from
EPA registered labels for chlorine dioxide, sodium chlorite, and sodium
chlorate.

b	Amount handled per day values are based on Residential SOPs, industry
sources, and AD estimates.	

c	Dermal unit exposures are from CMA and PHED studies. 

d	Baseline dermal:  Long-sleeve shirt, long pants, and no gloves.

e	PPE dermal with gloves: baseline dermal plus chemical-resistant
gloves.

f	Dermal dose (mg/kg/day) = [unit exposure (mg/lb ai) * dermal
absorption (1.0) * Appl. rate * amount handled / Body  weight (60 kg).

g	MOE = NOAEL  (mg/kg/day) / daily dose [Where short-and
intermediate-term dermal NOAEL = 3 mg/kg/day].  Target MOE is 100.

	

Table 6.3.  E-FAST/CEM Model Inputs and Results for the Fruit/Vegetable
Rinse Scenario

Parameter	Value	Rationale

Inputs

Weight Fraction of Chemical in Product	0.073	Based on maximum use rate
listed on product label

Hand Surface Area/Body Weight Ratio	15.6 cm2/kg	Derived from both hands
being immersed in the dip solution (E-FAST default value for general
purpose cleaner scenario,Versar, 1988)

Film Thickness	0.00214 cm	Assumed to be the initial thickness of water
uptake on hands from handling a rag (E-FAST default value for general
purpose cleaner scenario,Versar, 1988)

Density of Formulation	0.032 g/cm3	Based on information from label (0.27
lb ai/gal = 0.032 g/cm3)

Dilution Fraction	0.015	Derived from information on product label (1.9
oz/gal = 0.015 gal/gal)

Frequency of Events per Year	130 event/yr	Assumed 5 days/week for 50
weeks/yr

Number of Years of Use	57 yrs	Assumed to be total number of years
between the ages of 18 and 75

Amount Retained on Skin	0.000001 g/cm2	Derived from product of the film
thickness on the skin’s surface and the density of the formulation and
the dilution factor

Calculated Results

Potential Dermal Dose Rate	1.14e-03 mg/kg-day	ADRpot output from model

(see Appendix B)

Calculated MOE	2600	MOE = NOAEL / Daily Dose [Where dermal NOAEL = 3
mg/kg/day].



Table 6.4.  Short-, Intermediate-, and Long-Term Risks Associated with
Post Application Exposure to Metalworking Fluids treated with Chlorine
Dioxide (Machinist)

Continuous Feed Method % a.i.

(EPA Reg. No. 9150-2)	Dermal Inputs	Daily Dermal Dose (mg/kg/day) (a)
ST/IT/LT Dermal MOE 

(Target MOE = 100) (b)

	Hand Surface Area (cm2)	Film thickness (mg/cm2)	Frequency (event/day)



0.00001	840	1.75	1	0.00025	12,000



a	Dermal daily dose (mg/kg/day) = [(% active ingredient * hand surface
area* dermal absorption factor (100% for all durations)* film thickness
(mg/cm2)* frequency (event/day)] / body weight (60 kg).

b  	Dermal MOE = NOAEL (mg/kg/day) /  daily dose (mg/kg/day) [Where:
ST/IT/LT NOAEL = 3 mg/kg/day from an oral study 	assuming 100% dermal
absorption].

		6.1.2	Inhalation Handler Exposures

	Inhalation exposure to the release of chlorine dioxide gas during the
mixing/loading/application of products producing chlorine dioxide may
occur.  Because the inhalation toxicological endpoint is based on an
8-hour TWA, the assessment of handler inhalation exposures is assessed
as a combination of activities throughout a work day.  The assessment of
inhalation exposure is presented in the post application/bystander
section (Section 6.2).  

	As indicated above, EPA has selected an 8-hour TWA inhalation endpoint.
 EPA does not provide a separate endpoint for short-term exposures to
handlers.  Short-term releases of chlorine dioxide are of concern for
accidental releases/leaks and/or when applicators are in close proximity
to open solutions of chlorine dioxide.  EPA assumes that the ACGIH 15
minute short term exposure limit (STEL) of 0.3 ppm as well as the
immediately dangerous to life or health (IDLH) limit of 5 ppm will be
adhered to in the industries using chlorine dioxide.

	6.2 	Occupational Post Application/Bystander Exposure  tc "6.2
Occupational Postapplication Exposure " \l 2 

		6.2.1	Dermal Post Application/Bystander Exposures

	No information is available to assess post application/bystander dermal
exposure to uses in agricultural premises as well as food handling,
commercial/institutional and medical premises; human drinking water
facilities; industrial processes; and retention ponds.  However, dermal
post application exposure to chlorine dioxide is expected to be less
than that of the dermal contact of children playing on treated floor
surfaces.  Therefore, the dermal exposure route is not believed to be of
concern in these industries.  

		6.2.2	Inhalation Post Application/Bystander Exposures

Non-Fogging Uses

	There is the potential for the off gassing of chlorine dioxide during
some applications that are not totally enclosed (e.g., spray aqueous
solution, mopping, pouring, etc).  	Although no occupational air
monitoring data have been submitted to assess the inhalation route, EPA
has obtained air concentration measurements from OSHA.   OSHA maintains
a data base known as the Integrated Management Information System
(IMIS).  The IMIS entries for chlorine dioxide are available for 7
industry Standard Industrial Classification (SIC) codes.  Specific uses
such as applicators, bystanders and the activities involved are not
available.  The SIC codes representing the chlorine dioxide data in IMIS
used in this assessment include:  

SIC 0723  Crop preparation services for market;

SIC 1629  Heavy construction;

SIC 2611  Pulp mills;

SIC 2621  Paper mills;

SIC 2819  Industrial inorganic chemicals;

SIC 2836  Biological products; and

SIC 3999 Manufacturing industries.  

	The data selected for this analysis include only those samples that are
reported as 8-hour TWA measurements from personal air samplers.  Other
samples, such as peaks concentrations and/or area monitors, have been
omitted.  The chlorine dioxide sampling and analytical procedures used
in the collection of the data in IMIS are available at   HYPERLINK
"http://www.osha.gov/dts/sltc/methods/inorganic/id202/id202.html" 
http://www.osha.gov/dts/sltc/methods/inorganic/id202/id202.html .  The
quantitative LOD from this method is 0.004 ppm for a 4-hour sample (the
recommended sampling time).  The reported full 8-hour work shift
samples are based on two 4-hour samples collected in sequence.  The
inhalation endpoint selected by EPA is 0.003 ppm, just below the OSHA
LOD for an 8-hour TWA air sample [i.e., (0.5 x 0.004 ppm per 4 hrs) +
(0.5 x 0.004 ppm per 4 hrs)=0.004 ppm per 8 hours].

	The summary results of the 33 observations taken from 8-hour TWA
personal air samplers for chlorine dioxide are provided below in Table
6.5.  All values, including ½ LOD are above the EPA selected inhalation
reference concentration (RfC) of 0.003 ppm, and therefore, are of
concern.  Of the 33 TWA measurements available, 21 of those measurements
were below the LOD of 0.004 ppm.  In addition, of the 33 TWA
measurements, only 3 were at or above the OSHA PEL of 0.1 ppm.  For
nondetected samples, 1/2 the detection limit for an 8-hour sample was
used to determine the summary.

Table 6.5.  Chlorine Dioxide 8-hour TWA for Personal Air Samplers from
OSHA’s IMIS Data Base.

Statistic	Chlorine Dioxide 8-hr TWA (ppm)	MOE

Arithmetic mean ± std	0.034 ± 0.096	Note:  The inhalation endpoint is
expressed as the RfC.  Because the uncertainty factors are included in
the RfC a separate MOE is not needed.  The occupational RfC of 0.003 ppm
is compared directly to the air concentration monitored for the worker. 
Air concentrations above the RfC are of concern.  All values, including
the LOD, are above the RfC.

50th%tile	0.004 (1/2 8-hr LOD)

	75th%tile	0.008

	90th%tile	0.032

	Maximum	0.42

	Number of Observations	33

	Number of Nondetects	21

	

Fogging Uses

	The fogging use of chlorine dioxide is unique such that no persons are
present during the actual application/fogging.  There is also a greater
potential for chlorine dioxide gas formation from fogging then an
aqueous-based application such as mopping.  Therefore, a separate
assessment is presented for foggers that indicate potential inhalation
exposure and reentry recommendations.  The air concentration in a fogged
area should be below the occupational RfC of 0.003 ppm before the room
is entered by persons not wearing respiratory protection.  In the
fogging assessment below, EPA Reg. No. 74602-2 is used to illustrate
potential air concentrations.  

	Concentrations of chlorine dioxide were estimated for buildings after
fogging applications.  Air concentrations were calculated using the
Multi-Chamber Concentration and Exposure Model (MCCEM v1.2).   MCCEM
estimates average and peak indoor air concentrations of chemicals
released from products or materials in houses, apartments, townhouses,
or other residences. Although the data libraries contained in MCCEM are
limited to residential settings, the model can be used to assess other
indoor environments.  MCCEM has the capability to estimate inhalation
exposures to chemicals, calculated as single day doses, chronic average
daily doses, or lifetime average daily doses.

	The product, EPA Reg # 74602-2 (sodium chlorite with a 5% chlorine
dioxide equivalent) has a maximum application rate for egg houses of
0.0083 lb ai/gal (1000 ppm chlorine dioxide treatment solution).  This
particular product specifically lists a Dramm fogger for the application
(i.e., ultra low volume (ULV)).  According to the registrant, the Dramm
fogger for chlorine dioxide applications uses 2.5 ounces of the diluted
product per 225,000 cubic feet (USEPA 2006), and the label states to run
the fogger for five minutes.  Note:  This labeled rate should be added
to all chlorine dioxide fogger uses.  If other registrants require a
higher application rate, these rates need to be brought to EPA’s
attention during the development of the chlorine dioxide RED.  

	Model input assumptions for MCCEM and the calculated exposures are
presented in Tables 6.6 and 6.7 for 0.18 ACH and 4 ACH, respectively. 
The following assumptions were made:

The area being fogged is a one-chamber barn with dimensions of 300 ft x
50 ft x10 ft (AD standard assumption).

Two different air exchange rates (kACH) were used in the calculations: 
0.18 air exchange per hour (ACH) (MCCEM default based on a poorly vented
residential home) and 4 ACH based on the rate for a poultry barn
(Jacobson, 2005).

 , and substituting 0.5 hours for “t”, the rate of decay is
calculated to be 1.386/hr.

 .  This value was used for the “Air Exchange Rate” in the MCCEM
model to account not only for the air exchange, but also the decay.  

Fogging occurs instantaneously, so that the entire mass of product is
mixed homogeneously with the indoor air as soon as fogging commences. 

	The initial concentrations of chlorine dioxide, as indicated in Tables
6.6 and 6.7, is 0.0116 mg/m3 or 0.004 ppm.  Using an ACH of 0.18, an
8-hr TWA of less than 0.003 ppm (0.0084 mg/m3) is expected with no REI. 
Using an ACH of 4/hr, an 8-hr TWA of less than 0.003 ppm (0.0084 mg/m3)
is expected without an REI.  A detailed report is presented in Appendix
C, including hourly air concentrations.  Although there appears to be no
inhalation risks of concern, a 1-hour REI would be prudent.  Moreover,
potential label language to assure proper ventilation if rates above
that used in this assessment are identified for existing products
include:

	--ten air exchanges, or

--2 hours of mechanical ventilation (i.e., fans), or

--4 hours of passive ventilation (i.e., windows, vents), or

--11 hours of no ventilation followed by 1 hour of mechanical
ventilation, or

--11 hours of no ventilation followed by 2 hours of passive ventilation,
or 

	--24 hours of no ventilation

Table 6.6.  Short and Intermediate Term Inhalation Risks Associated with
Post Application Exposure to Chlorine Dioxide After Fogging   

0.18 ACH

Parametera	Value	Rationale

Dimensions	300x50x10 ft,

15,000 ft2 floor area,

150,000 ft3 (4,248 m3)

volume	EPA assumption

Air Changes per Hour (ACH)*	1.566/hr	Value used in MCCEM is actually the
ACH rate (0.18/hr) plus the decay rate (1.386/hr)a

Activity Pattern*	8-hour Time Weighted Average (TWA) starting
immediately, 1 hour, and 12 hours after fogging	Based on product(s
re-entry interval 

(EPA Reg# 74602-2)

Application Rate	0.0083 lb ai/gal	Product label

Use Rate	2.5 oz/225,000 ft3	Manufacturer’s specifications

Amount Applied to Room	1.16x10-5 g/m3	(Use rate) x (Application rate)

Concentration in Room after Fogging (initial concentration rate at time
0)*	0.0116 mg/m3	Amount applied to room

MCCEM Output

Average Concentration over 8-hrs (mg/m3)	0-hr re-entry: 	0.00109	Average
of MCCEM-calculated air concentrations from Hour 0 to Hour 8

Average Concentration over 8-hrs (mg/m3)	1-hr re-entry: 	0.000227
Average of MCCEM-calculated air concentrations from Hour 1 to Hour 9

Occupational RfC

(i.e., level-of-concern)	8-hour TWA	0.0084(mg/m3) 	Level-of-concern not
exceeded

*Used as MCCEM input.  Default values from MCCEM were used for all
inputs not listed in the table above

  and substituting 0.5 hours for “t”, the rate of decay is
calculated to be 1.386/hr.

Table 6.7.  Short and Intermediate Term Inhalation Risks Associated with
Post application Exposure to Chlorine Dioxide After Fogging 

4 ACH

Parametera	Value	Rationale

Dimensions	300x50x10 ft,

15,000 ft2 floor area,

150,000 ft3 (4,248 m3)

volume	EPA assumption

Air Changes per Hour (ACH)*	5.386/hr	Value used in MCCEM is actually the
ACH rate (4.0/hr) plus the decay rate (1.386/hr)a

Activity Pattern*	8 hour Time Weight Average (TWA) starting immediately,
30 minutes, and 1 hour after fogging	Based on product(s re-entry
interval 

(EPA Reg# 74602-2)

Application Rate	0.0083 lb ai/gal	Product label

Use Rate	2.5 oz/225,000 ft3	Manufacturer’s specifications

Amount Applied to Room	1.16x10-5 g/m3	(Use rate) x (Application rate)

Concentration in Room after Fogging (initial concentration rate at time
0)*	0.0116 mg/m3	Amount applied to room

MCCEM Output

Average Concentration over 8-hrs (mg/m3)	0-hr re-entry: 	0.000475
Average of MCCEM-calculated air concentrations from Hour 0 to Hour 8

Average Concentration over 8-hrs (mg/m3)	1-hr re-entry: 	2.18x10-6
Average of MCCEM-calculated air concentrations from Hour 1 to Hour 9

Occupational RfC

(i.e., level-of-concern)	8-hour TWA	0.0084(mg/m3)	Level-of-concern not
exceeded

*Used as MCCEM input.  Default values from MCCEM were used for all
inputs not listed in the table above

  and substituting 0.5 hours for “t”, the rate of decay is
calculated to be 1.386/hr.

	In a second fogging example, EPA Reg. No. 21164-3 allows chlorine
dioxide fogging and misting applications while workers are in the room
if the level of chlorine dioxide does not exceed the TLV-TWA of 0.1 ppm.
 The use directions are as follows:

“…may be added to the plant misting or fogging systems to deodorize
and to control odor causing bacteria, mold and mildew in food processing
plants, dairies, bottling plants, poultry, meat and fish plants and
animal facilities such as poultry houses, swine pens, calf barns and
kennels.  If the TLV-TWA is to be exceeded, turn off air handlers and
vacate people and livestock from the rooms to be fogged or misted. 
Ventilate for 15 minutes prior to reentry.  Note – Be careful not to
add concentrated acid solutions to undiluted DURA KLOR as high
concentrations of chlorine dioxide gas may evolve.  The concentration of
chlorine dioxide in the diluted DURA KLOR solution should not be allowed
to exceed 0.5 ppm…”

	The occupational RfC of 0.003 ppm could be exceeded based on these use
directions (i.e., workers do not need to leave treatment area unless the
TLV-TWA of 0.1 ppm is exceeded).

EPA’s Risk-based RfC versus OSHA PEL

	It is also important to note that the OSHA PEL for chlorine dioxide is
0.1 ppm.  Air concentrations above the PEL are assumed to be mitigated
at each facility.  Facilities using chlorine dioxide are not required to
mitigate inhalation exposures until the air concentration reaches 0.1
ppm.  Based on the occupational inhalation toxicological endpoint
selected for chlorine dioxide (i.e., RfC of 0.003 ppm), levels at or
near the PEL are of concern.  In fact, the capability (i.e., LOD) of the
OSHA sampling method is insufficient for the occupational RfC presented
in this document.  Reconciliation of the EPA risk-based RfC and the
current OSHA standards will be made during the regulatory decision phase
of the Reregistration Eligibility Decision (RED) for chlorine dioxide. 
The various cited chlorine dioxide levels from other organizations are
reported in Table 6.8 for review by regulatory managers.

Table 6.8  Chlorine Dioxide Regulatory Levels.

Organization	Time/Duration	Description	Air Concentration (ppm)

OSHA	8-hour TWA	PEL	0.1

ACGIH	8-hour TWA	TLV	0.1

	15-minutes	STEL	0.3

NIOSH	10-hour TWA	REL	0.1

	30-minutes (escape)	IDLH	5

EPA	8-hour TWA	RfC - Occupational	0.003

	“Short-term”	RfC – Residential for single exposures	0.05

	Continuous (24/7)	RfC – Residential 	0.00007

   

	6.3	Data Limitations/Uncertainties  tc "6.3	Data
Limitations/Uncertainties " \l 2 

	There are several data limitations and uncertainties associated with
the occupational handler and post application exposure assessments. 
These include:

The exposure factors used to calculate daily exposures to handlers are
based on applicable data, if available.  For lack of appropriate data,
values from a scenario deemed similar enough by the assessor were used. 

The inhalation toxicological endpoints of concern for the occupational
and long-term residential scenarios/durations are below the limit of
detection for chlorine dioxide.

Specific application techniques and/or worker activities are not
available in OSHA’s IMIS data base.  

Surrogate dermal unit exposure values were taken from the proprietary
Chemical Manufacturers Association (CMA) antimicrobial exposure study
(MRID 42587501) or from the Pesticide Handler Exposure Database (PHED,
1998).  See Appendix A for summaries of these data sources. 

The amounts handled/treated were estimated based on information from
various sources, including the Draft Standard Operating Procedures
(SOPs) for Residential Exposure Assessments (2000) and the Draft SOPs
for Occupational Exposure Assessments (2003).  In certain cases, no
standard values are available for some scenarios.  Assumptions for these
scenarios are based on AD estimates and could be further refined from
input from affected sectors.

7.0	REFERENCES tc "7.0		REFERENCES" 

42587501	Popendorf, W.; Selim, M.; Kross, B. (1992) Chemical
Manufacturers Association Antimicrobial Exposure Assessment Study:
Second Replacement to MRID 41761201: Lab Project Number: Q626.
Unpublished study prepared by The University of Iowa. 316 p.

ATSDR.  2004.  Agency for Toxic Substances and Disease Registry (ATSDR)
Toxicological Profile For Chlorine Dioxide and Sodium Chlorite, US
Department of Health and Human Services.  September 2004.

BCI, 2002.  HVAC air monitoring study.

Gates, Don.  1998.  The Chlorine Dioxide HANDBOOK.   AWWA Publishers.

Helwig, D. (2003) Personal Communication between D. Helwig (Johnson
Diversy, Inc) and K. Riley (Versar, Inc.), November 11, 2003.

Oak Ridge National Laboratory.  2005.  Risk Assessment Information
System.  http://risk.lsd.ornl.gov/tox/tox_values.shtml

PHED Surrogate Exposure Guide.  1998.   Estimates of Worker Exposure
from the Pesticide Handler Exposure Database Version 1.1. August, 1998.

Speronello, Barry.  1998.  Worst-Case Release Study for Automotive
Deodorizing Products.  Engelhard Corporation, Iselin, NJ.  Completed
date March 12, 1998.

Speronello, Barry.  2005.  Chlorine Dioxide Concentration Over a Carpet
Treated with Sanitizer 71 Powder.  Engelhard Corporation, Iselin, NJ. 
Completed date January 18, 2005.

U.S. EPA. 1991.  Chemical Engineering Branch Manual for the Preparation
of Engineering Assessments.  Prepared for the OPPT by IT Environmental
Programs, Inc.

USEPA.  1992.  Dermal Exposure Assessment:  Principles and Applications.
 Interim Report.  Office of Research and Development, Washington, D.C. 
January 1992.  EPA/600/8-91/011B.

USEPA.  1997.  Exposure Factors Handbook. Volume I-II.  Office of
Research and Development.  Washington, D.C.  EPA/600/P-95/002Fa.

USEPA.  2000.  Residential SOPs.  EPA Office of Pesticide
Programs–Human Health Division. Dated April 5, 2000.

USEPA.  2001.  HED Science Advisory Council for Exposure. Policy Update,
November 12.  Recommended Revisions to the Standard Operating Procedures
(SOPs) for Residential Exposure Assessment, February 22, 2001.

USEPA.  2005a.  Chlorine Dioxide/Sodium Chlorite -   SEQ CHAPTER \h \r 1
Report of the Hazard Identification Assessment Review Committee (HIARC)
and the Antimicrobials Division Toxicity Endpoint Selection Committee
(ADTC).   Dated March 29, 2005. 

USEPA. 2005b.  Sodium Chlorate: Occupational and Residential Exposure
Assessment of Antimicrobial Uses for the Reregistration Eligibility
Decision Document.  PC Code 073301, RED Case No. 4049, DP Barcode
D3112200.

USEPA.  2005c.  Exposure Determination from a Indoor Disinfectant
(One-Time) Use of Chlorine Dioxide.  Dated July 20, 2005.

USEPA.  2006.  Personal communication between Tim Leighton (EPA) and Ken
Howlett (Verox).  January 27, 2006.

Versar, Inc. 1988. Standard Scenarios for Estimating Exposure to
Chemical Substances During Use of Consumer Products.

Wood, Richard and Gallo, Vanessa.  1997.  Aseptrol Automotive Field
Testing:  Chlorine Dioxide Air Levels Inside Vehicle.  Engelhard
Corporation, Iselin, NJ.  Completed date November 14, 1997.

APPENDIX A: Summary of CMA data and PHED tc "APPENDIX A\: Summary of
CMA data and PHED" 

Chemical Manufacturers Association (CMA) Data:

In response to an EPA Data Call-In Notice, a study was undertaken by the
Institute of Agricultural Medicine and Occupational Health of The
University of Iowa under contract to the Chemical Manufacturers
Association.  In order to meet the requirements of Subdivision U of the
Pesticide Assessment Guidelines (superseded by  Series 875.1000-875.1600
of the Pesticide Assessment Guidelines), handler exposure data are
required from the chemical manufacturer specifically registering the
antimicrobial pesticide.   The applicator exposure study must comply
with the assessment guidelines for “Applicator Exposure Monitoring”
in Subdivision U and the “Occupational and Residential Exposure Test
Guidelines” in Series 875.  For this purpose, CMA submitted a study on
28 February, 1990, entitled "Antimicrobial Exposure Assessment Study
(amended on December 8, 1992)" which was conducted by William Popendorf,
et al.  It was evaluated and accepted by Occupational and Residential
Exposure Branch (OREB) of Health Effect Division (HED), Office of
Pesticides Program (OPP) of EPA in 1990.  The purpose of this CMA study
was to characterize exposure to antimicrobial chemicals in order to
support pesticide reregistrations (CMA, 1992).  The unit exposures
presented in the most recent EPA evaluation of the CMA database (U.S.
EPA, 1999) were used in this assessment.

The Agency determined that the CMA study had fulfilled the basic
requirements of Subdivision U - Applicator Exposure Monitoring.  The
advantages of CMA data over other “surrogate data sets” is that the
chemicals and the job functions of mixer/loader/applicator were defined
based on common application methods used for antimicrobial pesticides. 
A few of the deficiencies in the CMA data are noted below:

	The inhalation concentrations were typically below the detection
limits, so the unit exposures for the inhalation exposure route could
not be accurately calculated. 

	QA/QC problems including lack of either/or field fortification,
laboratory recoveries, and storage stability information.

	Data have an insufficient amount of replicates.

The Pesticide Handlers Exposure Database (PHED):

The Pesticide Handlers Exposure Database (PHED) has been developed by a
Task Force consisting of representatives from Health Canada, the U.S.
Environmental Protection Agency (EPA), and the American Crop Protection
Association (ACPA).  PHED provides generic pesticide worker (i.e.,
mixer/loader and applicator) exposure estimates.  The dermal and
inhalation exposure estimates generated by PHED are based on actual
field monitoring data, which are reported generically (i.e.,
chemical-specific names not reported) in PHED.  It has been the
Agency’s policy to use “surrogate” or “generic” exposure data
for pesticide applicators in certain circumstances because it is
believed that the physical parameters (e.g., packaging type) or
application technique (e.g., aerosol can), not the chemical properties
of the pesticide, attribute to exposure levels. [Note: Vapor pressures
for the chemicals in PHED are in the range of E-5 to E-7 mm Hg.] 
Chemical specific properties are accounted for by correcting the
exposure data for study specific field and laboratory recovery values as
specified by the PHED grading criteria.

PHED handler exposure data are generally provided on a normalized basis
for use in exposure assessments.  The most common method for normalizing
exposure is by pounds of active ingredient (ai) handled per replicate
(i.e., exposure in mg per replicate is divided by the amount of ai
handled in that particular replicate).  These unit exposures are
expressed as mg/lb ai handled.  This normalization method presumes that
dermal and inhalation exposures are linear based on the amount of active
ingredient handled.



APPENDIX B: Input/Output from E-FAST/CEM tc "APPENDIX B\: Input/Output
from E-FAST/CEM" 



   CEM Inputs	ID Number: Unknown

Product: Fruit/vegetable rinse	Chemical Name: Sodium Chlorite

Scenario: User Defined	Population: Adult

Weight Fraction - Median (unitless):	0.073



Weight Fraction - 90% (unitless):	0.073



Dermal Inputs

Frequency of Use - Body (events/yr): 	130	SA/BW - Body (cm2/kg):	15.6

Assume 5 days/week for 50 weeks/yr     	Derived from both hands being
immersed in the dip solution (E-FAST default value for general purpose
cleaner scenario) 

Amount Retained/Absorbed to Skin (g/cm2-event):  	1e-06

	Derived from product of the film thickness on the skin’s surface
(assumed to be the initial thickness of water uptake on hands from
handling a rag: 0.00214 cm; E-FAST default value for general purpose
cleaner scenario) and the density of the formulation (0.27 lb ai/gal =
0.032 g/cm3) and the dilution factor (1.9 oz/gal = 0.015 gal/gal)       

       

     	 



   Avg. Time, LADD (days):	2.74e+04	Avg. Time, ADD (days):	2.08e+04

   Avg. Time, ADR (days):	1.00e+00





CEM Dermal Exposure Estimates

ID Number: Unknown

	Scenario: User Defined	Population: Adult

Years of Use (years): 57

	SA/BW Body (cm2/kg): 15.6	 

Frequency of Use (events/year): 130	 





Exposure Units	Result	AT (days)



Chronic Cancer





  LADDpot (mg/kg-day)	3.08e-04	2.74e+04



Chronic Non-Cancer





  ADDpot (mg/kg-day)	4.06e-04	2.08e+04



Acute





  ADRpot (mg/kg-day)	1.14e-03	1.00e+00









LADD - Lifetime Average Daily Dose (mg/kg-day)



ADD - Average Daily Dose (mg/kg-day)



ADR - Acute Potential Dose Rate (mg/kg-day)





	

Note: 75 years = 2.738e+04 days				pot - potential dose

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1998

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