  SEQ CHAPTER \h \r 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

 OFFICE OF                  

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES        

November 20, 2006			

					

MEMORANDUM			

SUBJECT:	Revised Occupational and Residential/Bystander Assessment of
the Antimicrobial Use (Remedial Wood Treatment) of Chloropicrin for the
Reregistration Eligibility Decision (RED) Document (Phase 3 Comment
Period).  PC Code 081501, DP Barcode D314388.

FROM:		Tim Leighton, Environmental Scientist

				Antimicrobials Division

TO:			Nathan Mottl  SEQ CHAPTER \h \r 1 , Chemical Review Manager

Special Review and Reregistration Division

	This memorandum provides a revised  SEQ CHAPTER \h \r 1  review of the
occupational applicator and residential bystander assessment for the
antimicrobial remedial wood treatment use of chloropicrin to support the
Reregistration Eligibility Decision (RED) document.  Revisions are based
on the Phase I registrant “error only” correction review comments. 
This assessment utilized the toxicological endpoints reviewed by the
Human Studies Research Board (HSRB) and selected by the Health Effects
Division (HED).  Readers are referred to USEPA (2006a) for a compete
discussion of the HSRB ethical and scientific review.

  SEQ CHAPTER \h \r 1 EXECUTIVE SUMMARY

	

	The Antimicrobials Division (AD) assessed the occupational and
potential bystander risks to the remedial wood treatment uses of
chloropicrin (e.g., poles, timbers, etc.).  This risk assessment is
based on a qualitative assessment of the uses.  Although the exposures
are expected to be minimal, the inhalation toxicological endpoints
selected for chloropicrin are in parts per billion (ppb).  To mitigate
potential dermal and inhalation exposure as well as eye irritation, PPE
has been recommended.  Use direction recommendations for the label are
also provided to mitigate the potential for residential bystander
exposure.  Revisions to the original review (USEPA 2006b) include
characterization of the chloropicrin-specific uses based on the Phase I
“error only” correction comments.  No changes have been made by AD
to the toxicological endpoints or uncertainty factors as suggested in
the Phase I comments.  HED will review these comments as appropriate
(the Phase I comments have been forwarded to HED).

1.0		Introduction

	

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 The Special Review and
Registration Division (SRRD) requested that the Antimicrobials Division
(AD) conduct a human health risk assessment for the remedial wood
treatment use of chloropicrin.  The Health Effects Division (HED) has
the lead to develop the risk assessment for chloropicrin RED document
(i.e., trichloronitromethane, CAS # 76-06-2), including the selection of
the toxicological endpoint for use in the risk assessment.

2.0		  SEQ CHAPTER \h \r 1 Toxicological Endpoints of Concern

	Table 1 presents the acute toxicity categories as outlined in the HED
risk assessment (USEPA 2006a). 

Table 1. Acute Toxicity Categories for Chloropicrin

Study Type	Toxicity Categorya

Acute Oral Toxicity	I

Acute Dermal Toxicity	I

Acute Inhalation Toxicity	II

Primary Eye Irritation	I

Primary Dermal Irritation	I

Dermal Sensitization	Not tested (corrosive)

	

Table 2 presents the inhalation endpoints selected by HED for the risk
assessment of chloropicrin (USEPA 2006a).	

Table 2. Summary of Toxicological Dose and Endpoints for Use in
Chloropicrin Human Health Inhalation Risk Assessment

Risk Assessment	Study	NOAEL/LOAEL	Endpoint	HED HC or HEC

Acute Inhalation	Non-occupational	Human Irritation Study	BMCL10= 0.073
ppm	Eye irritation, ↑ nasal nitric oxide & change in air flow 	HC =
0.073 ppm

UF = 10

	Occupational	Human Irritation Study	BMCL10= 0.073 ppm	Eye irritation,
↑ nasal nitric oxide & change in air flow	HC = 0.073 ppm

UF = 10

Short- and Intermediate-  Inhalation Term (1-6 months exposure)

	Non-occupational	13-Week Inhalation Study in Mice	NOAEL = 0.3 ppm

LOAEL = 1.0 ppm	Nasal and lung damage, increased lung weights	HEC =
0.008 ppm

UF = 30

	Occupational	13-Week Inhalation Study in Mice	NOAEL = 0.3 ppm

LOAEL = 1.0 ppm	Nasal and lung damage, increased lung weights	HEC =
0.035 ppm

UF = 30

Long-term Inhalation(> 6 months)	Non-occupational	78-Week Cancer Study
in Mice	NOAEL = 0.1 ppm

LOAEL = 0.5 ppm	Nasal discharge, nasal and lung damage, increased lung
weights, body weight loss	HEC = 0.004 ppm

UF = 30

	Occupational	78-Week Cancer Study in Mice	NOAEL = 0.1 ppm

LOAEL = 0.5 ppm	Nasal discharge, nasal and lung damage, increased lung
weights, body weight loss	HEC = 0.015 ppm

UF = 30

Cancer	Chloropicrin is currently not considered a carcinogen.



3.0		Remedial Wood Treatment (Occupational)

	Chloropicrin is used to control internal wood decay caused by fungi and
insects in wood timbers, poles, pilings, and glue-laminated beams (e.g.,
bridge timbers).  There are currently 7 registered labels for remedial
wood treatment by several different companies, each product containing
approximately 99 percent chloropicrin as a liquid.  Although packaged as
a liquid, chloropicrin has a high vapor pressure of 23.8 mmHG at 25C,
and therefore, there is the potential exposure to the vapor phase.  

	Specific label use directions indicate that chloropicrin is a
restricted use pesticide that is either poured or injected into
pre-drilled holes.  One label describes the application technique as
“using special Osmose equipment and prescribed techniques”. 
However, no other information is provided on this specialized equipment.
 Label directions also indicate that the amount of chloropicrin used per
pole is based on the size of the pole (or cubic foot of laminated
beams).  Pole applications range from 3 ounces of product for small
poles (e.g., distribution poles) up to 2 pints of product for large
poles (e.g., transmission poles).  Chloropicrin is poured or injected
into pre-drilled holes which are drilled at 45 degrees downward.  The
holes are placed approximately 6 to 8 inches apart at 90 degrees.  After
application, each hole is capped with a plastic or treated wooden plug. 
Some labels (e.g., EPA Reg. No. 66330-47) indicate that “a vapor
barrier wrap may be needed to confine chemical vapor”.   Some labels
have more specific application instructions then others.  Only a brief
application description is provided here.  More details on applications
techniques are available (Wilhelm 2006) and it is suggested that all of
the 7 registered products provide a complete description of product
application.  

The personal protective equipment (PPE) listed on the labels include
long pants, long sleeved shirts, chemical resistant footwear, and
chemical resistant gloves.  Most of the labels include a statement “Do
NOT wear goggles” in the general description of PPE.  However, some of
the labels with this statement also indicate under the heading of the
wood preservative use that the applicator needs to wear safety goggles
when capping the hole to avoid splashing.  These contradictory
requirements need to be rectified on some of the labels.  The label
warning statements not to wear goggles is because chloropicrin is a
lachrymator (i.e., tear producing eye irritant) and experience may have
shown goggles to be problematic.  According to Wilhelm (2006),
“utilities require the use of full-face respirators…”.  Therefore,
in lieu of goggles listed on some labels, face shields should be the
preferable option.  Finally, respiratory protection is also listed on
labels.  Respiratory requirements are indicated if chloropicrin air
concentrations exceed 0.1 ppm (Note:  EPA Reg. Nos. 75340-1 and 75341-3
list an air concentration of 0.3 ppm as the cutoff for respiratory
protection).  The 0.1 ppm label criterion is not listed as a time
weighted average (TWA) but rather “not to exceed”.  To determine the
air concentration of chloropicrin, various detectors are listed on the
labels such as Bendix Gastec Precision Gas Detector and
Matheson-Kitagawa detector.  The 0.1 ppm concentration referenced on
some of the labels is the OSHA Permissible Exposure Limit (PEL).  The
PEL is based on a TWA, not a ceiling.  A Short Term Exposure Limit
(STEL) has not been set for chloropicrin.  The revised Immediately
Dangerous to Life or Health Concentration (IDLH) is 2 ppm.

There is the potential for occupational dermal and inhalation exposure
to the applicator during open pouring or injection of chloropicrin into
pre-drilled holes prior to plugging.  To determine the appropriate
exposure duration (i.e., short-, intermediate-, or long-term) for
endpoint selection, the frequency of chloropicrin-specific applications
to poles has been revised based on Phase I comments (Wilhelm 2006). 
Wilhelm (2006) indicates the following use information for chloropicrin
treatments:

Distribution Poles - the smaller diameter wooden distribution poles
(~140 million distribution poles in service) are treated at a high end
rate of 42 per day with an annual average daily treatment range from 0
to 30 poles per day.  Workers treat these types of poles as their main
work function, treating 4 days per week, on a yearly basis (i.e., 175
days/year). 

Transmission Poles - the larger wooden transmission poles are treated at
a high end rate of 32 per day with an annual average daily treatment
range from 0 to 22 poles per day.  Workers treat these types of poles as
their main work function, treating 4 days per week, on a yearly basis
(i.e., 175 days/year). 

Based on these estimates, applicator exposure duration for both
distribution and transmission poles are both considered long-term.

Dermal Exposure and Risks:

	The potential for dermal exposure from application of chloropicrin may
occur during the injection or pouring up to 2 pints per pole of the
undiluted product directly into the pre-drilled holes or by filling
vials to be placed into holes in timber.  Potential dermal exposure may
also occur during the process of pouring chloropicrin from original
packaging containers into smaller containers prior to injecting or
pouring into the pre-drilled holes.  No postapplication dermal exposure
is expected (i.e., treated holes are capped/plugged and contact with
treated poles occurs infrequently).

	The risks associated with dermal applicator exposure are not
quantified.  PPE such as long pants, long sleeved shirts, and chemical
resistant gloves are recommended to mitigate skin irritation effects
resulting from potential dermal exposure to chloropicrin.  The following
discussion of dermal exposure/risk, excerpted from the HED’s
toxicological endpoint selection, also applies to the remedial wood
treatment applications:

“Chloropicrin is classified as category I (corrosive) for skin
irritation potential (rabbit) and acute dermal toxicity (rat).  Based on
the effects shown in the acute dermal toxicity and corrosivity studies,
HED is not currently requiring a subchronic dermal toxicity study. 
Dermal exposure to chloropicrin of any significance is not expected
based on the delivery systems used (e.g., soil injection or drip
irrigation) and emission reduction technologies (e.g., tarping).  The
physiochemical properties of chloropicrin also make significant dermal
exposure unlikely and quantifying any potential low level exposures very
difficult.  Therefore, a quantitative dermal exposure assessment has not
been completed.  Since HED does not have adequate data to quantify
dermal risk, PPE for dermal protection should be based on the acute
toxicity of the end- use product as described in the Worker Protection
Standard and mitigation measures for dermal exposure described in PR
Notice 93-7.”

Note:  PR Notice 93-7 was issued for chloropicrin and
chloropicrin/methyl bromide products when the WPS was implemented in
1993.  Products containing chloropicrin alone (Supplement 4A to PR
Notice 93-7) required long sleeve shirt, long pants, chemical-resistant
gloves (when handling the liquid), chemical-resistant apron (when
handling the liquid), chemical-resistant footwear plus socks, and
protective eyewear.

Inhalation Exposure and Risks:

	As with the dermal exposure above, the potential for inhalation
exposure to chloropicrin vapor may occur during the transfer from
original packaging into smaller application containers or vials and
during the injection or pouring of up to 2 pints per pole of the
undiluted product directly into the pre-drilled holes.  Exposure during
the placement of prefilled vials into drilled holes should not occur
unless the vials are accidentally damaged.  Negligible postapplication
occupational inhalation exposure is expected (i.e., workers remaining in
the vicinity of treated poles would occur infrequently).

	Inhalation toxicological endpoints selected include acute, short-,
intermediate-, and long-term exposure durations.  Workers applying
chloropicrin as a remedial wood treatment are expected to be exposed up
to a long-term duration.  Workers are expected to be exposed to various
concentrations of chloropicrin throughout the work day with peak
concentrations occurring during open pouring of the products. 
Applications are performed outdoors and the product is capped into
pre-drilled holes, thereby reducing the potential for off gassing
immediately after the application.  No air concentration measurements
are available for these types of applications.  

Based on the use pattern (i.e., intermittent exposures throughout the
work shift), the acute inhalation endpoint selected for chloropicrin is
a good indicator of the need for respiratory and eye protection.  The
acute inhalation toxicological endpoint for chloropicrin, based on an
increase in nasal nitric oxide and change in air flow derived from a
human irritation study, is 0.073 ppm with a 10x uncertainty factor (UF).
 This endpoint also represents the eye irritation level-of-concern (LOC)
for chloropicrin (i.e., LOC = 0.073 ppm/10x UF = 0.0073 ppm).  In this
human study, irritation to the eyes, nose, and/or throat were observed
after 1 hour exposures repeated over 4 consecutive days.  This LOC,
0.0073 ppm, is lower then the current level listed on the product labels
(i.e., OSHA PEL of 0.1 ppm) used to determine if respiratory protection
is needed.

In addition to the acute assessment, a long-term exposure duration is
also of relevance.  Although the intermittent nature of the chloropicrin
inhalation exposure throughout the work day in ambient conditions would
presumably result in a minimal concentration as a time weighted average
(TWA), the long-term inhalation endpoint is very sensitive (i.e., level
of concern (LOC) = 0.015 ppm / 30x uncertainty factor = 0.0005 ppm), and
therefore, may be of concern.  Moreover, the long-term LOC selected for
chloropicrin would most likely be below the limits of detection for
detector tubes that could reasonably be used in the field.  Therefore, a
quantified risk assessment is not possible at this time.

4.0		Bystander/Residential Exposure and Risks

	In general, remedial wood treatment for poles and beams on bridges do
not occur in high traffic areas for bystanders.  However, distribution
poles are numerous and often located in people’s front yards. 
Therefore, any potential bystander exposure would be best represented by
the acute duration.  There is no air monitoring data available to
determine if chloropicrin vapor is released in the vicinity of treated
poles.  To minimize the escape of the chloropicrin gas from treated
poles, specific use directions should be listed on all of the labels
(some labels already list these directions, but not all).  The types of
use directions that will minimize the potential for vapors to be
released to be available for bystander exposure include:

plug the pre-drilled holes immediately after chloropicrin applications;

use a barrier wrap on treated wood, where needed, to confine the vapor;

do not treat drilled holes if they intersect internal rot pockets or
splits; and

do not treat structures/beams indoors.

Note:  USEPA (2004b) indicated a poisoning incident (incident #5358-1)
resulting from a pole treatment near an uncapped riser/open conduit
allowing chloropicrin fumes to enter a post office located 75 to 80 feet
away.  According to Wilhelm (2006), application procedures have been
modified to avoid these circumstances in the future.

5.0		Conclusions

	To mitigate the potential applicator dermal exposure to the irritant
effects of chloropicrin, PPE such as long pants, long sleeved-shirts,
and chemical resistant gloves are required.  In addition, some type of
eye protection is also required but the label requirement for goggles
listed on some of the products should be modified to face shields (see
discussion above).  To mitigate the potential inhalation risks to
applicators, respiratory protection is recommended that during the
actual pouring of chloropicrin between containers and/or vials and
during pouring/injecting into the pre-drilled holes.  This
recommendation is based on the need to protect applicators when air
concentrations are above the acute level-of-concern of 0.0073 ppm and
the TWA of 0.0005 ppm.  The minimum type of respiratory protection to
require is difficult to determine because the actual air concentration
in the vicinity of the applicator is unknown.  Therefore, the specific
type of respirator (e.g., SCBA) is a decision for the regulatory manager
and should be made in consultation with the registrants to determine
what is feasible for applicators to wear while climbing poles. 

	To minimize the potential for bystander exposure from the off gassing
of chloropicrin treatments, specific label use directions are proposed. 
These directions currently exist on some of the labels but should be
recommended for all of the labels.

References

USEPA.  2004a.  Metam Sodium:  Occupational and Residential Exposure
Assessment of Antimicrobial Uses for the Reregistration Eligibility
Decision Document.  PC Code 039003 (Metam Sodium) and 068103 (MITC). 
Memorandum Dated August 19, 2004.

USEPA.  2004b.  Review of Chloropicrin Incident Reports. DP Barcode
D306838.  Memorandum Dated August 24, 2004.

USEPA.  2006a.  Chloropicrin: Revised HED Human Health Risk Assessment
for Phase 3; DP Barcode: D314380, PC Code: 081501.

USEPA.  2006b.  Occupational and Residential/Bystander Assessment of the
Antimicrobial Use (Remedial Wood Treatment) of Chloropicrin for the
Reregistration Eligibility Decision (RED) Document.  PC Code 081501, DP
Barcode D314388.  Memorandum from Tim Leighton (USEPA) to Nathan Mottl
(USEPA) dated September, 28, 2006.

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