UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

September 10, 2008

MEMORANDUM

SUBJECT:	Naphthalene:  Phase 4 Amendment:  Response to Comments In
Reference to “Naphthalene: Occupational and Residential Exposure
Assessment and Recommendations for the Reregistration Eligibility
Decision Document”

	

PC Code:  055801	DP Barcode:  355720

MRID No.:  43716501	Registration No.:  N/A

Petition No.:  N/A	Regulatory Action:  Phase 4

Risk Assessment Type:  Response to Comments	Case No.:  0022

TXR No.:  N/A	CAS No.:  91-20-3

MRID No.:  43716501	40 CFR:  N/A (Non-Food/ Non-Feed)



			

FROM:	Wade Britton, MPH, Industrial Hygienist

		Reregistration Branch 3

		Health Effects Division (7509P)					

THROUGH:	Catherine Eiden, Branch Chief

		Reregistration Branch 3

		Health Effects Division (7509P)

TO:		Molly Clayton

		Reregistration Branch 3

		Special Review and Reregistration Division (SRRD) (7508P)

This document serves a response to incorporate public and internal
comments received during the Phase 3 comment period.  This memorandum
supersedes the document, Naphthalene:  Phase 4 Amendment:  Response to
Comments in Reference to “Naphthalene: Occupational and Residential
Exposure Assessment and Recommendations for the Reregistration
Eligibility Decision Document” (W. Britton, D355008).

 Table of Contents

  TOC \o "1-3" \h \z \u    HYPERLINK \l "_Toc192045115"  Executive
Summary	  PAGEREF _Toc192045115 \h  3  

  HYPERLINK \l "_Toc192045116"  1.0	Background Information	  PAGEREF
_Toc192045116 \h  7  

  HYPERLINK \l "_Toc192045117"  1.1	Purpose and Criteria for Conducting
Exposure Assessments	  PAGEREF _Toc192045117 \h  7  

  HYPERLINK \l "_Toc192045118"  1.2 Toxicological Endpoints	  PAGEREF
_Toc192045118 \h  7  

  HYPERLINK \l "_Toc192045119"  1.3 Incident Report	  PAGEREF
_Toc192045119 \h  10  

  HYPERLINK \l "_Toc192045120"  1.4	Summary of Use Patterns,
Formulations, and Application Methods	  PAGEREF _Toc192045120 \h  10  

  HYPERLINK \l "_Toc192045121"  2.0	Residential Exposure and Risk	 
PAGEREF _Toc192045121 \h  13  

  HYPERLINK \l "_Toc192045122"  2.1 Residential Handler Noncancer
Exposure and Risk	  PAGEREF _Toc192045122 \h  13  

  HYPERLINK \l "_Toc192045123"  2.1.1 Residential Handler Noncancer
Exposure and Risk Estimates	  PAGEREF _Toc192045123 \h  14  

  HYPERLINK \l "_Toc192045124"  2.1.2	Residential Handler Cancer
Exposure and Risk	  PAGEREF _Toc192045124 \h  18  

  HYPERLINK \l "_Toc192045125"  2.2	Residential Postapplication Exposure
and Risks	  PAGEREF _Toc192045125 \h  18  

  HYPERLINK \l "_Toc192045126"  2.2.1 Residential Postapplication
Inhalation Exposure and Risk	  PAGEREF _Toc192045126 \h  19  

  HYPERLINK \l "_Toc192045127"  2.2.2 Residential Postapplication
Inhalation Exposure and Risk Estimates	  PAGEREF _Toc192045127 \h  19  

  HYPERLINK \l "_Toc192045128"  2.2.3 Residential Postapplication Cancer
Exposure and Risk	  PAGEREF _Toc192045128 \h  23  

  HYPERLINK \l "_Toc192045129"  2.2.4 Residential Postapplication
Episodic Ingestion Exposure and Risk	  PAGEREF _Toc192045129 \h  23  

  HYPERLINK \l "_Toc192045130"  2.2.5 Residential Postapplication
Episodic Ingestion Exposure and Risk
Estimates………………………………………………………
……………………  PAGEREF _Toc192045130 \h  23  

  HYPERLINK \l "_Toc192045131"  References	  PAGEREF _Toc192045131 \h 
25  

  HYPERLINK \l "_Toc192045132"  APPENDIX A	  PAGEREF _Toc192045132 \h 
26  

  HYPERLINK \l "_Toc192045133"  A.  Introduction	  PAGEREF _Toc192045133
\h  27  

  HYPERLINK \l "_Toc192045134"  B.  Residential Applicator Exposure and
Risk	  PAGEREF _Toc192045134 \h  27  

  HYPERLINK \l "_Toc192045135"  C.  Residential Postapplication Episodic
Ingestion Exposure and Risk	  PAGEREF _Toc192045135 \h  28  

 

	

Executive Summary

Background and Purpose

  SEQ CHAPTER \h \r 1 This occupational and residential exposure and
risk assessment is being conducted as part of EPA’s human health risk
assessment for the naphthalene Reregistration Eligibility Decision
(RED).  This document addresses the exposures and risks associated with
occupational and residential exposure to naphthalene based upon
prescribed label uses.  

Naphthalene Use Summary

According to the 3/28/2007 SMART meeting and EPA databases, registrants
are supporting two pesticide uses of naphthalene registered in the U.S. 
These are a moth treatment for the protection of woolen clothing
(indoor) and an animal repellant against nuisance vertebrate pests
(indoor and outdoor).  All registered products of naphthalene are
intended for residential uses only.  Residential products for use within
the home are formulated as mothballs or flakes, while outdoor products
are formulated as dusts, flakes, and granules.

Occupational Exposure and Risk Estimates

Naphthalene products are not registered for occupational use and,
therefore, occupational exposure to and risk from the pesticidal uses of
naphthalene is not anticipated and has not been assessed.  

Residential Applicator Exposure and Risk Estimates

HED has determined that there is potential for short-term (1-30 days)
exposure in residential settings during the application process for
homeowners who purchase and use naphthalene-containing products.  HED
anticipates handler dermal and inhalation exposure during the
application process; however, appropriate inhalation handler exposure
data are not available to assess this scenario, therefore, only dermal
exposure was assessed.  Applications of naphthalene can be made indoors
and outdoors and are expected to be short-term in duration due to the
intermittent nature of use associated with these products.  

Margins of Exposure (MOEs) for residential handlers were calculated
using standard assumptions and the results of an exposure study,
“Estimation of Homeowner Exposure to LX1298-01 (Naphthalene) Resulting
from Simulated Residential Use as an Insect Repellent (MRID
43716501),” in which dermal handler exposure data was derived from the
monitoring of a person weighing out and placing mothballs in a closet
and dresser at three different locations. 

Residential handler MOEs (indoor and outdoor) are > 100 and, therefore,
not of concern to HED.  Overall dermal exposure to handling naphthalene
products, indoors and outdoors, is expected to be insignificant.

Residential Indoor Postapplication Noncancer Exposure and Risk Estimates


HED has determined that there is potential for adult and toddler
exposure from naphthalene applications made indoors for moth treatments
and indoors/outdoors for animal repellency.  While labels specify that
treated indoor areas should be airtight to be effective, HED anticipates
that naphthalene will volatilize and be inhaled by adults accessing
treated areas (i.e., containers, dresser drawers, closets, etc.) and by
adults and toddlers that inhabit treated areas exposed to ambient
concentrations of naphthalene. Exposures from accessing treated areas
are expected to be acute in duration and exposures from inhabiting
treated areas are short-, intermediate- (1-6 months), and long-term (>6
months) in duration.  

Because of uncertainties associated with species differences between
humans and rodents in metabolism and respiratory toxicity studies,
rather than quantifying inhalation risks to humans, the levels of
ambient naphthalene measured in the human exposure study were compared
directly to the levels resulting in 1) no adverse effects in the rodent
studies (NOAELs) and 2) a toxic effect in rodents (LOAELs).  This
comparison provides a sense of the difference between actual naphthalene
concentrations that a human may encounter and the doses which elicit
either no adverse response or a toxic response in rodents. 

Anticipated acute and short-term exposures were calculated using
standard assumptions and the results of the aforementioned exposure
study (MRID 43716501).  Inhalation exposure data from the study apply to
exposure durations ranging from 15 minutes (person accessing treated
closets and dresser drawers) to 24 hours (average air concentration
surrounding treated closets, dresser drawers, and beds).  Anticipated
acute and short-term inhalation exposures to naphthalene in residences
are 20X and 30X below the animal dose (NOAEL), respectively. 
Anticipated acute and short-term inhalation exposures to naphthalene in
residences are 60X and 80X, respectively, below the animal dose (LOAEL)
resulting in respiratory toxicity (olfactory epithelium lesions),
respectively. 

Anticipated intermediate- and long-term exposure durations were also
calculated using standard assumptions; however, because of the lack of a
naphthalene-specific study of an appropriate duration, a different
exposure study was used to assess these durations of exposure
(Polycyclic Aromatic Hydrocarbon Exposure of Children in Low-Income
Families, Chuang et al., 1999).  This study was conducted to observe
exposures to polycyclic aromatic hydrocarbons (PAHs) inside of 24 homes
from air, dust, soil, and food.  This study is not specific to
intermediate- or long-term exposure durations, nor does naphthalene
necessarily originate from a mothball source; however, it has been
identified as the best data source to account for naphthalene
volatilization and dissipation over time in the home.  Due to the
uncertainty associated with the use of an exposure study which is not
specific to the duration assessed, HED selected the most conservative
exposure value (i.e., maximum concentration observed) to represent
intermediate- and long- term exposure levels.  Based on the highest
measured naphthalene levels from this study, intermediate-term exposures
to naphthalene in residences are 540X below the rodent dose (NOAEL)
resulting in no adverse health effects.  [Note: a NOAEL was not
identified in the chronic inhalation studies (rodents) for long-term
exposure so that comparison has not been done].  Intermediate- and
long-term exposures to naphthalene in residences are 1000X and 5400X
below the rodent dose (LOAEL) resulting in respiratory toxicity
(olfactory epithelium lesions), respectively.

Generally, in the absence of information on kinetics/dynamics, it is
assumed that humans may be 10 times more sensitive than animals (10X
interspecies factor).  The current research indicates that humans are
less sensitive than rodents because of differences in rate of
bioactivation of naphthalene as well as anatomical and physiological
differences in the nose and respiratory tract.  These critical
differences between primates and rodents have not been accounted for in
this assessment.  Thus, with consideration of differences in dosimetry
and species metabolism of naphthalene, the margins of exposure for human
inhalation risk assessment are likely larger than the differences
calculated here between the rodent NOAELs and LOAELs and the ambient
naphthalene levels. 

Studies determining the differences in nasal metabolism of naphthalene
between rodents and primates are part of ongoing research.  There are no
data to indicate that humans have a slower rate of clearance, but if
they did, then there would be a longer time for humans to produce the
active metabolite.  These issues are being addressed in current
pharmacokinetic model research.

Residential Indoor Postapplication Cancer Risk Estimates 

A quantification of cancer risk for exposures via inhalation, or
derivation of an inhalation reference concentration (RfC) for the
nonfood-pesticidal uses of naphthalene was not performed in this
assessment.  This is because there is support from published studies and
ongoing research on naphthalene that indicate that risk estimates,
factoring in known species differences between rodents and humans
(including humans) in metabolism and respiratory toxicity, would be
considerably less than those using default procedures.

Residential Episodic Ingestion Postapplication Exposure and Risk
Estimates

HED has determined there is potential that a toddler may ingest
formulations used for indoor or outdoor treatments of naphthalene.  In
order to assess this exposure route, HED estimated the risk of a toddler
ingesting a single mothball.  In addition, HED estimated the amount of a
single mothball that a toddler could ingest to result in an MOE = 100. 

While labels specify that indoor moth treatments be made in airtight
containers, it is assumed that a toddler could potentially access these
areas and ingest naphthalene products.  Incident data indicate that
ingestion of naphthalene by children primarily occurs by accessing
products labeled for indoor use.

Toddler episodic ingestion of one naphthalene mothball results in an MOE
< 100 and, therefore, is of potential concern to HED.  An oral dose of
0.5 mg/kg/day would be required to result in an MOE = 100.  This dose is
equivalent to toddler episodic (incidental) ingestion of 0.32% of one
mothball (7.5 of 2350 total mg).  While it is not expected that a
toddler would intentionally ingest an entire mothball, that scenario
cannot be completely discounted.

It is important to note that the resulting episodic ingestion MOE is
calculated from an endpoint derived from a developmental oral rat study
in which dams were treated with a high oral bolus dose and the resulting
clinical signs (lethargy and slow breathing) and body weight decrement
were transient.  The effects were attributed to the administration of a
high bolus and were not permanent; the animals displayed quick recovery.
 There were no persistent effects or treatment-related deaths.

The study results are consistent with what might be inferred from the
incident reports.  Reported incidents of naphthalene ingestion among
children account for the majority of reported exposures, and occur with
much greater frequency than for most other pesticides.  This may be
attributed to the widespread use of naphthalene products in homes and
the ease of accessing the product as it is applied as loose mothballs. 
The frequency and severity of the reported incidents are much lower than
for other pesticides as a whole.  From a 13-year period of Poison
Control Center data, only about 7% of naphthalene incidents in children
resulted in any symptoms at all and less than 1% had moderate or major
symptoms.  Symptoms that did occur (both adults and children; all routes
of exposure) were not life-threatening and included nausea, vomiting,
headache, dizziness, drowsiness/lethargy, eye irritation, and dermal
edema and erythema.

So while the episodic ingestion of naphthalene by a toddler may result
in an MOE less than the target MOE, and does present an exposure
concern, the effects of this type of exposure, if any, are not expected
to be severe.  Of greater concern is the accessibility of the product to
young children.  Limiting this accessibility will have a significant
impact on the number of incidents, including those which may result in
symptoms.

Recommendations and DCI Rationale

HED recommends that the registrant conduct an exposure study to
determine levels of naphthalene in indoor air resulting from simulated
residential mothball use over intermediate- and long-term durations. 
Intermediate- and long-term residential indoor postapplication exposure
and risk was estimated using surrogate data from an exposure study which
was conducted to determine indoor ambient levels of naphthalene.  Since
the surrogate exposure study was not duration- or use-specific, it may
potentially underestimate naphthalene exposure and risk.  An appropriate
study is required to confirm that the estimation of residential
postapplication inhalation exposure is protective of human health.  

Review of Human Research

This risk assessment relies in part on data from studies in which adult
human subjects were intentionally exposed to a pesticide or other
chemicals.  It was determined that the study, “Estimation of Homeowner
Exposure to LX1298-01 (Naphthalene) Resulting from Simulated Residential
Use as an Insect Repellent (MRID 43716501),” required review of its
ethical conduct, and has received that review.  It was concluded that
“there are no regulatory barriers to EPA’s reliance on this study in
its actions under FIFRA” (memorandum, J. Carley to Molly Clayton,
4/24/07).  The study, “Polycyclic Aromatic Hydrocarbon Exposure of
Children in Low-Income Families, Chuang et al., 1999,” was also
reviewed for its ethical conduct.  It was concluded that it “does not
meet the regulatory definition of research involving intentional human
exposure and is therefore not required to undergo ethical review” and
that “there are no regulatory, ethical, or policy barriers” to using
this study in the risk assessment (electronic communication, J. Carley
to Catherine Eiden, 2/20/08).

Background Information

Purpose and Criteria for Conducting Exposure Assessments

A residential exposure assessment is required for an active ingredient
if (1) certain toxicological criteria are triggered and (2) there is a
potential for exposure to handlers during use or to persons entering
treated sites after application is complete.  Naphthalene meets both
criteria.  There is potential for residential exposure to naphthalene
from application, inhabiting previously treated homes, and the episodic
(incidental) ingestion of the product. 

	1.2 Toxicological Endpoints

A summary of the acute toxicity data is included in Table 1. 
Naphthalene is acutely toxic in the rat via the oral (Category III) and
inhalation (Category II) routes of exposure.  In the rabbit, it is a
moderate acute dermal toxicant (Category III).   It is a moderate
(Category III) skin and eye irritant in the rabbit.  Naphthalene is not
a dermal sensitizer.

Table 1.  Acute Toxicity of Naphthalene



GDLN	

Study Type	

MRID	

Results	Tox

 mg/kg (♂+♀)	III

870.12	Acute Dermal	257229	LD50 >2000  mg/kg (♂+♀)	III

870.13	Acute Inhalation	257902	LC50 > 0.4 mg/L (77.7 ppm) (♂+♀)	II

870.24	Primary Eye Irritation	257228	Slight-moderate irritation	III

870.25	Primary Skin Irritation	257227	Moderate irritation	III

870.26	Dermal Sensitization	00148173	Nonsensitizer – guinea pig	N/A



The toxicological endpoints used to complete the residential exposure
assessment are summarized in Table 2.  The rationale for endpoints
selected for the assessment of residential risk can be referenced in the
document, Naphthalene:  Phase 4 Amendment: Response to Comments in
Reference to “Naphthalene:  HED Chapter of the Reregistration
Eligibility Decision Document (RED),” (D. Drew, D355719).

Table 2.  Toxicological Doses and Endpoints for Naphthalene for Use in
Human Health Risk Assessments

Exposure/

Scenario	Point of Departure	Uncertainty/ Safety Factors	Level of Concern
for Risk Assessment	Study and Toxicological Effects

Incidental Oral Exposures (Postapplication)

Incidental Oral (Short-term)	NOAEL= 50

mg/kg/day	UFA= 10x

UFH= 10x

	MOE= 100

	NTP Developmental Rat Study 

NOAEL = 50 mg/kg/day

LOAEL= 150  mg/kg/day based on maternal effects – transient clinical
signs of lethargy, slow breathing, rooting behavior, and significant
decreases in body weights/body weight gains and decreased food and water
consumption.

Dermal Exposures

Dermal (Short-Term)

	Dermal NOAEL= 300 mg/kg/day

	UFA= 10x

UFH= 10x

	MOE=  100

	90-Day Dermal Toxicity Study –Rat 

NOAEL = 300 mg/kg/day

LOAEL = 1000 mg/kg/day based on atrophy of seminiferous tubules in
males, and nonneoplastic lesions in the cervical lymph node
(hyperplasia), liver (hemosiderosis), thyroid thyroglossal duct cysts),
kidneys (pyelonephritis), urinary bladder (hyperplasia) and skin
(acanthosis, hyperkeratosis) in females.

Inhalation Exposures

*Inhalation (Short-term; 1-30 days)

	Inhalation 

LOAEL

= 10 ppm or 52 mg/m3

NOAEL 

= 3 ppm or

16 mg/m3	N/A

	N/A

	4-Week (Nose-Only) Inhalation – Rat

NOAEL = 3 ppm

LOAEL = 10 ppm based increased incidence and severity of nasal lesions
(slight disorganization, rosette formation, basal cell hyperplasia,
erosion, atrophy, and degenerate cells in the olfactory epithelium; loss
of bowman’s glands; respiratory epithelium hypertrophy; rosette
formation in the septal organ of Masera and fusion of the turbinates).  

*Inhalation (Intermediate-term; 1-6 months)

	Inhalation

LOAEL

= 2 ppm or 10 mg/m3

NOAEL

= 1 ppm or

5.2 mg/m3	N/A

	N/A	13-Week (nose-only) Inhalation Rat Study;   Subchronic (nose-only)
Neurotoxicity Rat Study 

NOAEL = 1 ppm (Subchronic neurotoxicity study)

NOAEL (13 week inhalation study) – not identified.

LOAEL = 2 ppm  (13 week inhalation study) based on increased incidence
and severity of nasal lesions (degeneration, atrophy and hyperplasia of
basal cells of the olfactory epithelium; rosette formation of olfactory
epithelium; loss of Bowman’s glands; hypertrophy of respiratory
epithelium).  

LOAEL = 10 ppm (subchronic neurotoxicity study) based on
atrophy/disorganization of the olfactory epithelium and hyperplasia of
the respiratory and transitional epithelium.  

*Inhalation (Long-term)

	Inhalation LOAEL

= 10 ppm or 52 mg/m3

	N/A

	N/A	NTP ChronicToxicity and Carcinogenicity Studies in the Rat and
Mouse

NOAEL – not identified.

LOAEL (rat study) = 10 ppm based on  increased incidence and severity of
atypical (basal cell) hyperplasia, atrophy, chronic inflammation, and
hyaline degeneration of the olfactory epithelium; hyperplasia, squamous
metaplasia, hyaline degeneration, and goblet cell hyperplasia of the
respiratory epithelium; and glandular hyperplasia and squamous
metaplasia.

Point of Departure (POD) = A data point or an estimated point that is
derived from observed dose-response data and  used to mark the beginning
of extrapolation to determine risk associated with lower environmentally
relevant human exposures.  NOAEL = no observed adverse effect level. 
LOAEL = lowest observed adverse effect level.  UF = uncertainty factor. 
UFA = extrapolation from animal to human (interspecies).  UFH =
potential variation in sensitivity among members of the human population
(intraspecies).  MOE = margin of exposure.  LOC = level of concern.  N/A
= not applicable.   

1.3 Incident Report

In order to complete the incident report for naphthalene (M. Hawkins and
H. Allender, D336085), four databases were consulted for poisoning
incident data.  These include: OPP Incident Data System (IDS), Poison
Control Centers (PCC), California Department of Pesticide Regulation,
and National Institute of Occupational Safety and Health’s Sentinel
Event Notification System for Occupational Risks (NIOSH SENSOR).  The
summary findings from the incident report for the period 1993 to 2005
for naphthalene are:

Naphthalene produces a higher proportion of acutely toxic incidents
requiring medical attention when compared to the composite average of
all other pesticides. There is a pattern of statistically significant
results in cases seen in a health care facility.  This pattern observed
in the combined population (occupational, non-occupational, children) is
largely due to the frequency and severity of pesticide poisoning among
children less than 6 years;

Exposure to children is much higher than a typical pesticide;

Naphthalene PCC data show average results of about 11,647
exposures/year, 133 symptomatic cases/year, and 310 cases/year seen in a
heath care facility; 

No apparent annual trend is evident in the 13 year-span of data
collected; and

NIOSH/SENSOR data indicate that indoor uses of naphthalene are
responsible for a large number of cases. 

Recommendations from the incident report for residential naphthalene use
are as follows:

In order to prevent exposures to children, actions restricting the
access to the active ingredient should be taken. This could include
packaging changes and other limitations to block children from coming
into contact with the active ingredient.

	Note: This will not address inhalation concerns.  

The reported symptoms resulting from naphthalene exposure include:
neurological (headache, dizziness, and drowsiness/lethargy),
gastrointestinal (nausea and vomiting), ocular (eye pain, irritation,
and inflammation, and lacrimation), respiratory (upper respiratory pain,
shortness of breath, coughing and choking).

 Summary of Use Patterns, Formulations, and Application Methods

Uses

Naphthalene is used as a moth treatment for the protection of woolen
clothing and as an animal repellant against nuisance vertebrate pests. 
All registered products of naphthalene are intended for residential uses
only.  The moth treatment use is registered for indoor only and is
labeled for treatment of indoor storage areas (containers, drawers, and
storage closets). The animal repellant use is labeled for indoor (attics
and wall voids) and outdoor (around the perimeter of domestic dwellings,
ornamental gardens, flower beds, lawns, or any area to be protected such
as wood piles, utility houses, barns, and trash cans) use.  

Mode of Action and Targets Controlled

Naphthalene is a white, crystalline solid which volatilizes to create a
characteristic odor.  In a sealed container, naphthalene vapors build up
to levels toxic to both the adult and larval forms of many moths
destructive to wool clothing.  In addition, naphthalene’s odor can be
used to repel vertebrate animals.  

Application Rates, Formulation Types, and Percent Active Ingredient

Naphthalene products for use within the home are formulated as mothballs
or flakes, while outdoor products are formulated as dusts, flakes, and
granules.  The percent of active ingredient of indoor-use products range
from 99.7 to 100%, and from 7 to 99.9% for outdoor-use products.  

Table 3 summarizes registered naphthalene products by formulation, use
site, formulation, percent active ingredient, and application rate.  

Table 3.  Summary of Registered Naphthalene Uses

Indoor Use

Product	Use Site	Formulation	% A.I.	App. Rate for the Area to be Treated

ENOZ® Old Fashioned Mothballs 

(1475-74)	Indoor storage areas (containers and storage closets)	Mothball
99.95	1 ounce per 3 ft3 - 

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

ENOZ® Old Fashioned Moth Flakes 

(1475-75)	Indoor storage areas (containers and storage closets)	Flake
99.95	1 ounce per 3 ft3 - 

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

ENOZ® Cedar Pine Mothballs

(1475-120)	Indoor storage areas (containers and storage closets)
Mothball	99.85	1 ounce per 3 ft3 -

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

Chaperone Squirrel and Bat Repellant 

(2724-685)	Attics and wall voids and indoor storage areas (containers
and storage closets)	Flake	100	1 pound per 400 ft3 

1 ounce per 3 ft3 - 

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

Dr. T’s Rabbit, Squirrel, Bat & Bird Repellant

(58630-2)

	Attics and wall voids	Flake	99.95	1 pound per 400 ft3



I-Ching Naphthalene Moth Balls 

(80305-1)	Indoor storage areas (containers and storage closets)	Mothball
99.9	1 ounce per 3 ft3 - 

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

IMS Old Fashioned Moth Balls 

(81433-6)	Indoor storage areas (containers and storage closets)	Mothball
99.95	1.5 ounces per 3 ft3 -

0.37 lb ai / Average Garment Bag (12 ft3)

0.36 lb ai / Large Trunk (15 ft3)

1.1 lb ai / Small Closet (50 ft3)

Moth Avoid Brand Traditional Moth Balls

(83424-2)	Indoor storage areas (containers and storage closets)	Mothball
99.7	1 ounce per 3 ft3 - 

0.25 lb ai  /  Average Garment Bag (12 ft3)

0.33 lb ai  /  Large Trunk (15 ft3)

1 lb ai       /  Small Closet (50 ft3)

Outdoor Use

F&B Rabbit and Dog Chaser

(4-465)	Soil treatment on ornamental plants, paved areas	Dust	 15	0.45
lb ai/ treated area (3 lb container)

(assuming entire contents used to treat area)

ENOZ® Skat!

(1475-146)	Around the perimeter of ornamental plants	Flake	99.45	2.5 lb
ai/ treated area (2.5 lb container)

(assuming entire contents used to treat area)

Dr. T’s Snake-A-Way Snake Repellant

(58630-1)	Around the perimeter of domestic dwellings (outdoors), wood
piles, utility houses, barns, trash cans, flower beds, and gardens
Granule	7	0.28 lb ai/treated area (4 lb container) 

2 lb ai/ treated area  (28 lb container)

(assuming entire contents used to treat area)

Dr. T’s Rabbit, Squirrel, Bat & Bird Repellant

(58630-2)	Around the perimeter of ornamental plants	Flake	99.95	4 lb ai/
treated area (4 lb container)

24 lb ai/ treated area (24 lb container)

(assuming entire contents used to treat area)



Timing of Applications

Registered labels for indoor, moth treatment use recommend keeping the
product in an airtight space for a minimum of seven days.  Re-treatment
is recommended when the mothballs have dissipated.  Since moths are
active all year, there is the potential for continual treatment indoors.
 One moth control label recommends re-treatment twice per year. 
Re-treatment for indoor/outdoor repellant uses are recommended as needed
to maintain odor intensity.  Hot weather, wind, and rain may diminish
the effectiveness of the product and necessitate re-treatment.   

Application Methods

Naphthalene treatments for indoor moth treatment use and indoor/outdoor
repellant use are labeled for application by hand. 

Residential Exposure and Risk

HED has determined that there is a potential for exposure in residential
settings during the application process for homeowners who purchase and
use products containing naphthalene.  There is also a potential for
postapplication exposure from inhabiting indoor areas previously treated
with naphthalene (inhalation), as well as, incidental toddler ingestion
of formulations used for indoor/outdoor treatments.  The exposure and
risk for homeowners applying naphthalene in the residential environment
is discussed in section 2.1.  

A quantitative exposure assessment was performed for homeowners applying
naphthalene in the residential environment and for toddler incidental
ingestion of naphthalene used for indoor/outdoor treatments.  Human
health risk estimates were not calculated for postapplication inhalation
scenarios because of the uncertainties associated with extrapolating
animal (rodent) data to humans as discussed previously in this document.
 Rather than quantifying inhalation risks to humans, the levels of
ambient naphthalene measured in the human exposure study were compared
directly to the levels resulting in a 1) no adverse effects in the
rodent studies (NOAELs) and 2) a toxic effect in rodents (LOAELs).  This
comparison provides a sense of the difference between actual naphthalene
concentrations that a human may encounter and the doses which elicit
either no adverse response or a toxic response in rodents.  

The residential indoor postapplication inhalation exposure comparisons
(human exposure study results and points of departure (LOAEL/NOAEL) from
animal studies) are discussed in Section 2.2.  Exposure and risk from
toddler incidental ingestion of naphthalene formulations used for
indoor/outdoor treatments is discussed in section 2.3.

2.1 Residential Handler Noncancer Exposure and Risk 

The Agency uses the term “handlers” to describe those individuals
who are involved in the pesticide application process.  The Agency
believes that there are distinct tasks related to applications and that
exposures can vary depending on the specifics of each task.    SEQ
CHAPTER \h \r 1 Job requirements (e.g., the amount of chemical to be
used in an application), the method of application, and the target being
treated can cause exposure levels to differ in a manner specific to each
application event.	

HED has determined that there is potential for exposure in residential
settings during the application process for homeowners who purchase and
use naphthalene-containing products.  According to label instructions,
homeowners must physically place naphthalene formulations into indoor
storage areas (containers and storage closets) and around the perimeter
of outdoor areas to be protected.  HED anticipates handler dermal
exposure during the application process; however, appropriate inhalation
handler exposure data are not available to assess this scenario and,
therefore, only dermal exposure was assessed.  

Data for acute (15 minute) exposure were used in conjunction with animal
studies to derive a direct comparison for postapplication inhalation
exposure to areas treated with naphthalene.  HED assumes that the acute
postapplication inhalation assessment is protective for handler
inhalation exposure since measured concentrations of naphthalene would
likely be greater due to the time allotted in the exposure study (4-6
days) for the product to accumulate in the enclosed areas that were
accessed. 

 

Applications of naphthalene are expected to be short-term in nature due
to the intermittent uses associated with the residential products.  As a
result, no intermediate-term or long-term assessments were assessed for
handlers.  

2.1.1 Residential Handler Noncancer Exposure and Risk Estimates

The residential handler exposure and noncancer risk calculations are
presented in this section. Noncancer risks were calculated using the MOE
as described in Appendix A, Section B.  The following scenarios were
assessed for handlers of naphthalene:

Hand application of naphthalene formulations for indoor moth treatments

Hand application of naphthalene formulations for indoor/outdoor animal
repellent treatments

Data Sources

Exposure data for acute and short-term residential handler exposure
durations were taken from the study, “Estimation of Homeowner Exposure
to LX1298-01 (Naphthalene) Resulting from Simulated Residential Use as
an Insect Repellent (MRID 43716501).” Dermal handler exposure data was
derived from the result of monitoring a person weighing out and placing
mothballs in a closet and dresser at three different locations. 

A summary of the exposure study is provided below with dermal handler
results presented in Table 4.  The following is a summary of naphthalene
exposure study, including the handler dermal and indoor air
concentration data sources used within for quantitative risk assessment
purposes.  The summary also encompasses the inhalation portion of the
exposure study with results presented in Tables 5 and 6. 

MRID 43716501:  Estimation of Homeowner Exposure to LX1298-01
(Naphthalene) Resulting from Simulated Residential Use as an Insect
Repellent. Review:  W. Britton, D340008

LX1298-01, a mothball formulation, containing 99.5% (0.995 g ai/g
product) of the active ingredient (ai) naphthalene, was applied as an
insect repellent by placing mothballs in a closet and a dresser drawer
at the maximum application rate of 1.0 lb ai/50 ft3 in designated
bedrooms at three different locations near Valdosta, Georgia.  The
person weighing out the mothballs and placing them in the closet and
dresser drawer at each location was monitored for inhalation exposure
and dermal exposure of naphthalene to the hands.  After the application,
the treated room was closed and not entered for three days.  At the
beginning of the fourth day, indoor air concentration sampling at three
locations within the treated room was monitored continuously for 8-hour
intervals for three consecutive days.  During a 12-hour period of each
sampling day (4, 5 and 6 days after treatment (DAT)) a worker wearing a
personal air sampling device (two-stage charcoal filter cartridge)
entered the treated room every two hours for a 15-minute sampling
duration to simulate a homeowner’s or worker’s daily activities in
the room.  Indoor air concentration samples were also collected at
three, 15-minute intervals during this same 12-hour period inside the
treated closet and inside the treated drawer. 

Dermal exposure to the applicator was determined by analysis of gloves
worn when weighing out and applying the test product.  The results of
inhalation exposure (15 minute) to the applicator were not written into
the Study Report.  

The overall average naphthalene applicator hand exposure (dermal) was
0.053 mg/lb ai, as summarized in Table 4.  Post-application inhalation
exposure and air concentration was monitored on Days 4, 5 and 6 after
the application. The overall average post-application inhalation
exposures (daily activities) for Days 4, 5 and 6 were 0.77 mg /m3, 0.87
mg /m3 and 0.90 mg /m3, respectively, as summarized in Table 5.  Results
of the air monitoring took place within the treated zones (dresser
drawer and closed closet); however, the Study Author only provided
naphthalene air concentrations for Hour 0, Hours 4-8, and Hour 12. 
These concentrations ranged for all three trials from 2.37 to 10.3 mg/m3
in the dresser drawer and from 1.49 to 12.29 mg/m3 in the closet for all
three days.  The air sampling devices monitoring the areas outside the
treated zone were placed just outside the closet, on top of the dresser
and adjacent to the head of the bed.   The average 24-hour naphthalene
air concentration on top of the dresser at all three test sites on Days
4, 5 and 6 ranged from 0.39 to 0.89 mg/m3.  The average 24-hour
naphthalene air concentration adjacent to the closet at all three test
sites on Days 4, 5 and 6 ranged from 0.43 to 0.81 mg/m3.  The average
24-hour naphthalene air concentration at the head of the bed at all
three test sites on Days 4, 5 and 6 ranged from 0.39 to 0.86 mg/m3.  A
summary of all average 24-hour air concentrations are summarized in
Table 6.



Table 4.  Applicator Hand Exposure ( mg/cm2)  Based on Cotton Glove
Dosimeters



Trial	

Naphthalene Residue - Both Hands (mg/lb ai)

	Contact Surface Area of Both Gloves

(cm2)	Naphthalene Hand Exposure

(mg/cm2)

92-298-01-21H-02	0.00807	407	1.98E-05

92-298-01-21H-03	0.104	407	2.56E-04

92-298-01-21H-04	0.0465	407	1.14E-04

Mean 	0.053	407	1.30E-04



Table 5. Post-Application Inhalation Exposure (Acute) –  (mg/m3)

Site #	Average

Day 4  Air Concentration  (mg/m3)	Average Day 5  Air Concentration 
(mg/m3)	Average Day 6  Air Concentration  (mg/m3)

92-298-01-21H-02	0.49	0.48	0.63

92-298-01-21H-03	0.85	1.1	1.3

92-298-01-21H-04	0.98	1.0	0.74

Overall Average	0.77	0.87	0.90



Mean	0.85 mg/m3



Table 6.  Postapplication Air Concentration of Naphthalene (Short-Term)
- (mg/m3)

Hours	Average 

Day 4 Naphthalene Air Concentration Adjacent to Dresser Drawer (mg/m3)
Average 

Day 5 Naphthalene Air Concentration Adjacent to Dresser Drawer (mg/m3)
Average 

Day 6 Naphthalene Air Concentration Adjacent to Dresser Drawer (mg/m3)
Average 

Day 4 Naphthalene Air Concentration Adjacent to Closet (mg/m3)	Average 

Day 5 

Naphthalene Air Concentration Adjacent to Closet (mg/m3)	Average 

Day 6 

Naphthalene Air Concentration Adjacent to Closet (mg/m3)	Average 

Day 4 Naphthalene Air Concentration Adjacent to Bed (mg/m3)	Average 

Day 5 Naphthalene Air Concentration Adjacent to Bed (mg/m3)	Average 

Day 6 

Naphthalene Air Concentration Adjacent to Bed (mg/m3)

92-298-01-21H-02

0 – 8	0.48	0.41	0.36	0.50	0.44	0.64	0.52	0.37	0.64

8 – 16	0.45	0.50	0.69	0.53	0.53	0.72	0.39	0.46	0.66

16 - 24	0.24	0.52	0.92	0.27	0.61	0.81	0.25	0.58	0.83

Avg.	0.39	0.48	0.66	0.43	0.53	0.72	0.39	0.47	0.71

92-298-01-21H-03

0 – 8	0.76	0.93	1.10	0.73	0.86	0.98	0.68	0.87	1.03

8 – 16	0.94	1.05	1.02	0.95	0.95	0.91	0.99	1.05	0.98

16 - 24	0.73	0.66	0.55	0.71	0.60	0.54	0.58	0.66	0.57

Avg.	0.81	0.88	0.89	0.80	0.80	0.81	0.75	0.86	0.86

92-298-01-21H-04

0 – 8	0.65	0.64	0.57	0.73	0.91	0.63	0.65	0.60	0.56

8 – 16	0.71	0.63	0.47	0.92	0.69	0.56	0.72	0.54	0.43

16 - 24	0.55	0.49	0.50	0.77	0.67	0.62	0.52	0.47	0.41

Avg.	0.64	0.59	0.51	0.81	0.76	0.60	0.63	0.54	0.47

Day/Site Avg.	0.61	0.65	0.69	0.68	0.70	0.71	0.59	0.62	0.68



Geometric Mean	0.66 mg/m3



Assumptions Regarding Residential Applicator Exposure

Homeowner handlers are expected to complete all tasks associated with
the use of a pesticide product (e.g., application);

The maximum application rate of 14.4 lb ai/ treated area was used for
indoor moth treatment risk calculations, assuming that 3 closets (600
ft3) and 3 dresser drawers (90 ft3) are treated at 0.0625 lb ai/ 3 ft3;

The maximum application rate of 24 lb ai/ treated area was used for
outdoor repellant treatment risk calculation, assuming the entire
contents of a 24 lb container is used for treatment at 99.95% ai; 

A body weight of 70kg was assumed because the endpoint is not gender
specific; 

Dermal absorption is assumed to be 100%, which is representative of a
conservative assumption of risk; and

Areas for chemical used in the risk assessment are based on Agency
guidance specific to residential use patterns.

Risk Summary

Table 7 presents the quantitative risks associated with both scenarios
considered for the residential handler noncancer assessment. Both dermal
handler scenarios assessed resulted in MOEs > 100 and, therefore, are
not of concern to HED.   

Table 7.  Naphthalene Noncancer Risks Attributable to Homeowner Handler
Exposures

Exposure Scenario	Total Applied

(lb ai)	Daily Exposure (mg/ lb ai)	MOE

(LOC = 100)

1 - Apply Moth Treatment by Hand	14.4	0.053	28000

2 – Apply Animal Repellant Treatment by Hand	24  	0.053	17000



Residential Handler Cancer Exposure and Risk

A quantification of cancer risk for exposures via inhalation, or
derivation of an inhalation reference concentration (RfC) for the
nonfood-pesticidal uses of naphthalene was not performed in this
assessment.  This is because there is support from published studies and
ongoing research on naphthalene that indicate that risk estimates,
factoring in known species differences between rodents and humans
(including humans) in metabolism and respiratory toxicity, would be
considerably less than those using default procedures. 

Residential Postapplication Exposure and Risks

The Agency uses the term “postapplication” to describe exposures to
individuals that occur as a result of working in an environment that has
been previously treated with a pesticide (also referred to as re-entry
exposure).  HED has determined that there is potential for adult
exposure from accessing treated areas and adult and toddler exposure
from inhabiting homes previously treated with naphthalene, as well as,
toddler exposure from the episodic (incidental) ingestion of
formulations used for indoor/outdoor animal repellency.  

	2.2.1 Residential Postapplication Inhalation Exposure and Risk

As previously described, naphthalene applications are made indoors for
moth treatments.  While labels specify that treated indoor areas (i.e.,
containers, dresser drawers, and storage closets) should be airtight to
be effective, HED anticipates that naphthalene will volatilize and be
inhaled by adults accessing treated areas (acute exposure) and by adults
and toddlers that inhabit treated areas exposed to ambient
concentrations of naphthalene (short-, intermediate-, and long-term
exposures). 

In lieu of an appropriate inhalation study for comparison to anticipated
acute (15 minute) exposures, HED used the short-term inhalation
endpoint.  The pairing of an acute inhalation exposure with a short-term
toxicity endpoint is likely to be conservative and protective of human
health for this route of exposure.  HED used appropriate endpoints from
short-, intermediate-, and long-term inhalation toxicity studies to
estimate risks for individuals inhabiting treated homes.  

	2.2.2 Residential Postapplication Inhalation Exposure and Risk
Estimates

The residential indoor postapplication inhalation exposure comparisons
(human exposure study results and points of departure (LOAEL/NOAEL) from
animal studies) are presented in this section. The following scenarios
were assessed:

Adult 

Acute inhalation from accessing treated areas 

Adult/Toddler 

Short-/intermediate-/long-term inhalation from inhabiting treated area 

Data Sources

Exposure data for acute and short-term residential postapplication
inhalation was taken from the exposure study, “Estimation of Homeowner
Exposure to LX1298-01 (Naphthalene) Resulting from Simulated Residential
Use as an Insect Repellent (MRID 43716501).”  Inhalation exposure data
was derived for accessing treated areas (15-minute duration) from the
results of air sampling of an individual accessing treated a treated
drawer and closet, and performing household tasks (i.e., dusting,
sitting in a chair, etc) in a treated room.  A summary of the exposure
study data is provided in Table 6.  Inhalation exposure data was derived
for inhabiting a treated area (short-term) was derived from the results
of indoor air sampling in enclosed rooms in 3 different locations. Air
samples were collected continuously (in 8-hour intervals) for 3
consecutive days from devices surrounding treated closets, dresser
drawers, and beds. A summary of the exposure study data is provided in
Table 5. 

Results of the registrant-submitted exposure study indicate that indoor
air concentrations of naphthalene range between 0.85 and 0.66 mg/m3 for
acute and short-term durations of exposure, respectively.  These results
fall well within the range (0.23 – 7.5 mg/m3) of naphthalene
concentrations observed in indoor air from mothball sources
(acute-/short-term duration) in the open literature and, therefore, are
not likely to underestimate naphthalene exposure for acute and
short-term durations. The following open literature sources were
identified for comparison:  

0.35 mg/m3 in a cupboard containing mothballs (Lau et al., 1995);

7.5 mg/m3 in a closet, 1.2 in a bedroom, 0.90 mg/m3 in a living room,
0.35 mg/m3 in a garage, and 0.23 mg/m3 outdoors of a home which had
closets treated liberally with mothballs (Gammage and Matthews, 1987);
and

0.68 mg/m3 from a living room of a home containing mothballs (Hawthorne
et al., 1985).

HED determined that the exposure data used to assess acute and
short-term exposure to indoor postapplication inhalation exposure to
naphthalene from mothball sources was not appropriate to assess
intermediate- and long-term exposure durations.  As described
previously, naphthalene volatilizes into the treated area and it is
assumed that adults and toddlers who inhabit these areas are potentially
exposed.  Based upon label application timing recommendations for moth
control, it is likely that re-treatment could occur, at a minimum, once
every 1-6 months.  The continued volatilization of naphthalene over time
results in a reduced concentration of the chemical and, likewise,
reduced potential for inhalation exposure.  Therefore, the exposure data
used for the acute and short-term duration likely overestimates the
concentration of naphthalene available for inhalation over longer term
durations.  HED was unable to identify an exposure data source which was
appropriate to assess intermediate- and long-term exposure to
naphthalene from a mothball source.  Exposure data was extrapolated,
however, from a study in the open literature which observed indoor
ambient concentrations of naphthalene in 24 homes.  This study is not
duration-specific, nor does naphthalene originate from a mothball
source; however, it has been identified as the best data source to
account for naphthalene volatilization over time.    

The following is a summary of the exposure study, “Polycyclic Aromatic
Hydrocarbon Exposure of Children in Low-Income Families,” with indoor
air naphthalene concentration results presented in Table 8.  

J. Chuang et al.  Polycyclic Aromatic Hydrocarbon Exposure of Children
in Low-Income Families.  Journal of Exposure Analysis and Environmental
Epidemiology.  (1999) 2, pp. 85-98.  

Humans can be exposed to polycyclic aromatic hydrocarbons (PAHs) by
inhaling contaminated air, by ingesting tainted food, by non-dietary
ingestion of contaminated dust or soil, or by dermal ingestion. 
Children of inner-city families are likely exposed to greater levels of
PAHs than children in rural areas based upon household proximity to
heavier traffic and more industrial sources.  A two-home pilot study
(1994) and a nine-home winter and summer study (1995) were conducted in
Durham and the NC Piedmont area with the following objectives:  to
establish methods for measuring total PAH exposure of children in
low-income families, to estimate the PAH exposures to these children,
and to estimate the relative importance of the environmental pathways
for PAH exposure.  In each study multimedia samples were collected and
analyzed for PAH or hydroxy-PAH.  For the purposes of this risk
assessment, HED used only the resulting concentrations of PAH
(specifically, naphthalene) of indoor, ambient air observed in the 24
low-income homes sampled.  

A total of 14 inner city and 10 rural homes were sampled in the study. 
All inner city homes were located in downtown Durham, NC, close to
either freeways and/or busy streets.  The rural homes were located away
from heavy traffic areas.  Homes were recruited on the basis of the
presence of an adult and a preschool, toilet-trained child living at
home; unvented combustion space heating; and family income below the US
Department of Health and Human Services (DHHS) poverty guidelines.  The
heating systems of the 24 homes were noted and included central electric
and gas heating, kerosene heaters, open-flame gas heaters, and
fireplaces.  Cooking appliances were electric and gas.  For the two-home
pilot study conducted in Durham, the field sampling activities were
completed in a 3-day period.  One home was occupied by nonsmokers, the
other by smokers.  The nine-home study was carried out using a revised
study protocol that monitored two home in 2 days and the summer studies
monitored three homes in 2 days.  Five inner city and four rural homes
inhabited by nonsmokers were recruited for the winter study.  Nine
nonsmokers’ (five inner city and four rural) and four smokers homes
(two inner city and two rural) were recruited for the summer study.  

In order to assess indoor concentrations of PAHs, indoor air samplers
and real-time PAH monitors were installed and a capillary adsorption
tube sampler (CATS) was deployed to measure air exchange rate.  Outdoor
air samples, as well as occupant food and urine sample collection took
place, but are not of significance to the current risk assessment.  The
indoor sampler was placed in either the living room or the family room
and was sampled for a 24 hour period within each home.  The PAH in air
were collected by passing air at 20 liters/minute through a sampling
cartridge containing a quartz fiber filter and XAD-2 resin in series. 
After sampling, the filter and XAD-2 samples were wrapped in clean
aluminum foil, placed in a clean container, sealed, and stored in a
freezer until being sent back to the laboratory for analysis.  The flow
rate of each sampler was checked and recorded at the initiation and at
the conclusion of the air sampling period.   

The mean, standard deviation, minimum and maximum values of naphthalene
concentrations in indoor air samples from the 24 low-income homes are
summarized in Table 8.  Of all PAH concentrations resulting, naphthalene
was the most abundant target PAH identified.  Results from the overall
study including indoor and outdoor air, and food and urine samples
indicated that inhalation is the most important pathway for adults’
and childrens’ exposure to total PAH and that levels of PAH in indoor
air were higher than in corresponding outdoor air in most households. 
Due to the uncertainty associated with the use of an exposure study
which is not duration- or use-specific, HED selected the most
conservative exposure value (i.e., maximum concentration observed) for
risk assessment purposes.   

Table 8.  Summary of Naphthalene Concentrations (mg/m3) in Indoor Air of
the 24 Low-Income Homes

Mean	Standard Deviation	Minimum	Maximum

0.0022	0.0019	0.00033	0.0097



 Assumptions Regarding Postapplication Inhalation

HED assumes that an individual could access treated areas (i.e.,
containers, dresser drawers, and storage closets) for an exposure
duration of 15 minutes; and

HED assumes that an individual could be exposed continually within their
home (i.e., 24 hours per day) for short-/intermediate-/long-term
duration.

Risk Summary

A comparison was performed between both the NOAELs and LOAELs from
rodent studies and human exposure studies.  For acute- and short-term
exposure scenarios, the results of an exposure study, “Estimation of
Homeowner Exposure to LX1298-01 (Naphthalene) Resulting from Simulated
Residential Use as an Insect Repellent (MRID 43716501)” were used.
 The 15 minute (acute) and 24 hour (short-term) samples resulted in
average concentrations of 0.85 and 0.66 mg/m3 of naphthalene,
respectively. These values were compared directly to the animal LOAEL
(10 ppm or 52 mg/m3) and NOAEL (3 ppm or 16 mg/m3) selected for acute
and short-term exposure durations.

 

Anticipated acute and short-term exposures to naphthalene in residences
are 60X and 80X, respectively, below the animal dose (LOAEL) resulting
in respiratory toxicity (olfactory epithelium lesions) and 20X and 30X
below the animal dose (NOAEL), respectively.    

 

For intermediate- and long-term durations, the results of an exposure
study, “Polycyclic Aromatic Hydrocarbon Exposure of Children in
Low-Income Families (Chuang et al., 1999) were utilized.”  The indoor
ambient samples which pertain to the air concentrations of naphthalene
resulted in a maximum level of 0.0097 mg/m3. This exposure value was
directly compared to the animal LOAEL for olfactory epithelium lesions
selected for intermediate- (2 ppm or 10 mg/m3 identified in a nose-only
study) and long-term (10 ppm or 52 mg/m3 identified in an exposure
chamber study) durations, as well as, the NOAEL selected for the
intermediate-term duration (1 ppm or 5.2 mg/m3).  A NOAEL was not
identified for long-term inhalation exposure.  

Intermediate- and long-term exposures to naphthalene in residences are
1000X and 5400X, respectively, below the animal dose (LOAEL) resulting
in respiratory toxicity (olfactory epithelium lesions) and
intermediate-term exposure is 540X below the animal dose (NOAEL).  The
long-term duration was not assessed since a NOAEL was not identified.  

								

	2.2.3 Residential Postapplication Cancer Exposure and Risk

A quantification of cancer risk for exposures via inhalation, or
derivation of an inhalation reference concentration (RfC) for the
nonfood-pesticidal uses of naphthalene was not performed in this
assessment.  This is because there is support from published studies and
ongoing research on naphthalene that indicate that risk estimates,
factoring in known species differences between rodents and humans
(including humans) in metabolism and respiratory toxicity, would be
considerably less than those using default procedures.

	2.2.4 Residential Postapplication Episodic Ingestion Exposure and Risk

As previously described, naphthalene applications are made indoors for
moth treatments and indoors/outdoors for animal repellency.  HED
anticipates that toddlers could come in contact with naphthalene
formulations inside a treated home or in treated outdoor areas.  While
labels specify that indoor moth treatments be made in airtight
containers, it is assumed that a toddler could potentially access these
areas and ingest naphthalene products.  Outdoor applications of
naphthalene are labeled for use around the perimeter of areas to be
protected.  While a toddler could potentially access outdoor treated
areas, HED believes that toddler episodic (incidental) ingestion
exposure is more likely to occur indoors.  Results of the incident
report support this belief (D336085).  In order to assess
postapplication episodic (incidental) ingestion of naphthalene, a
potential dose was derived from the assumption of a toddler ingesting
one mothball.  HED also estimated the amount of the mothball that could
be ingested by a toddler to result in an MOE = 100. 

Inhalation and episodic (incidental) ingestion routes of exposure were
not combined for toddlers in order to differentiate the occurrence of a
discrete accidental event (assessed to give a worst-case estimate of
risk) from the expected daily exposure via the inhalation route.  It
would not be appropriate to combine episodic exposure for comparison to
a short- (or longer) term endpoint.  

	2.2.5 Residential Postapplication Episodic Ingestion Exposure and Risk 
	         Estimates

The residential indoor/outdoor postapplication episodic (incidental)
ingestion exposure risk calculations are presented in this section.
Noncancer risks were calculated using the approach described in the
Standard Operating Procedures (SOPs) for Residential Exposure
Assessments, Section: 2.3.1, Postapplication – Incidental Nondietary
Ingestion.  SOPs were used to derive the potential dose rate of a
toddler ingesting one mothball, which was then compared to the
incidental oral endpoint to calculate an MOE.  In addition, HED
estimated the amount of a single mothball that a toddler could ingest to
result in an MOE = 100.  Appendix A, Section C presents the algorithms
used to determine these values.  

The following scenario was assessed for episodic (incidental) ingestion
of naphthalene formulations:

Toddler

Episodic (incidental) ingestion of naphthalene formulation from
indoor/outdoor exposure

Assumptions Regarding Toddler Episodic Ingestion

One mothball weighs 2.35 grams (or 2350 mg) and the maximum labeled
percent active ingredient is 99.95%;

For the purposes of this risk assessment, HED is assuming that a child
is only ingesting one mothball; and 

3 year old toddlers are expected to weigh 15 kg.

Episodic Ingestion Summary

Toddler episodic (incidental) ingestion of one naphthalene mothball
results in an MOE < 100 and, therefore, is of concern to HED.  An oral
dose of 0.5 mg/kg/day would be required to result in an MOE = 100.  This
dose is equivalent to toddler incidental ingestion of 0.32% of one
mothball (7.5 of 2350 mg).

Episodic Ingestion Risk Characterization

It is important to note that the resulting episodic ingestion MOE is
calculated from an endpoint derived from a developmental oral rat study
in which dams were treated with a high oral bolus dose and the resulting
clinical signs (lethargy and slow breathing) and body weight decrement
were transient.  The effects were attributed to the administration of a
high bolus and were not permanent; the animals displayed quick recovery.
 There were no persistent effects or treatment-related deaths.

The study results are consistent with what might be inferred from the
incident reports.  While reported naphthalene incidents among children,
specifically for ingestion which accounts for the majority of children
exposures, occur with much greater frequency than for most other
pesticides (apparently because of the widespread use of naphthalene
products in homes and the ease of accessing the product as it is
applied), the frequency and severity of the effects are much lower than
for other pesticides as a whole.  From a 13 year period of Poison
Control Center data, only about 7% of naphthalene incidents in children
resulted in any symptoms at all and less than 1% had moderate or major
symptoms.  Symptoms that did occur (both adults and children; all routes
of exposure) were not life-threatening and include nausea, vomiting,
headache, dizziness, drowsiness/lethargy, eye irritation, and dermal
edema and erythema. 

So while the episodic ingestion of naphthalene by a toddler may result
in an MOE less than the target MOE, and does present an exposure
concern, the effects of this type of exposure, if any, are not expected
to be severe.  Of greater concern is the accessibility of the product to
young children.  Limiting this accessibility will have a significant
impact on the number of incidents, including those which may result in
symptoms.

References

U.S. EPA 2007.  Naphthalene SMART Meeting, March 28, 2007

U.S. EPA 1997. “Draft Standard Operating Procedures for Residential
Exposure Assessments” U.S. Environmental Protection Agency, Office of
Pesticide Programs.  December 19, 1997.

EPA MRID 43716501 – “Estimation of Homeowner Exposure to LX1298-01
(Naphthalene) Resulting from Simulated Residential Use as an Insect
Repellent,” T. Bill Waggoner, October 7, 1994.

W. Britton, 2007.  Naphthalene:  Review of “Estimation of Homeowner
Exposure to LX1298-01 (Naphthalene) Resulting from Simulated Residential
Use as an Insect Repellent (MRID 43716501)” (D340008) June 21, 2007.

5.   J. Chuang et al.  Polycyclic Aromatic Hydrocarbon Exposure of
Children in    

      Low-Income Families.  Journal of Exposure Analysis and
Environmental 

     Epidemiology.  (1999) 2, pp. 85-98.

6.   M. Hawkins and H. Allender, 2007. Review of Naphthalene Incident
Reports   

      (D336085) June 25, 2007.

APPENDIX A

STANDARD FORMULAS USED FOR 

CALCULATING RESIDENTIAL 

EXPOSURES TO NAPHTHALENE

A.  Introduction

This section summarizes the algorithms used to calculate risk estimates
from residential exposures to naphthalene.   These formulas and a basic
description of how they are used were taken from Reference 2.  These
references also contain more detailed information on the rationale
behind these formulas.  Only those formulas that are pertinent to
naphthalene exposures are discussed in this document. 

B.  Residential Applicator Exposure and Risk

The basic rationale for this algorithm is that the daily exposure is the
product of the amount of active ingredient (ai) handled per day times a
unit exposure value.  The amount of ai handled per day is the product of
the application rate times the area treated.  For example, if 0.0625 lbs
of naphthalene are required to treat 3 ft3, and 3 closets and 3 dressers
drawers total 690 ft3, then the amount of naphthalene handled would be
14.4 lbs that day.  The unit exposure value is the amount of exposure
that results from handling a given amount of active ingredient by a
certain method.  The unit exposure value, 0.053 mg/lb ai, used for
dermal applicator exposure of naphthalene was derived from the
previously described exposure study (MRID 43716501).  In this example,
the daily exposure would be 14.4 lbs ai handled multiplied by 0.053 mg
unit exposure per pound of ai handled which equals 0.763 mg per day. 
The daily absorbed dose (mg/kg BW) is calculated from the exposure by
multiplying the exposures times an absorption factor (1.0) and dividing
the result by the body weight (70 kg).  In this example the daily dose
would be (0.763 mg/day *1.0)/ 70 kg which would equal 0.011 mg/kg/day. 
An MOE is calculated by dividing the endpoint for dermal exposure (300
mg/kg/day) by the daily dose (0.011 mg/kg/day), which would equal
28,000. 

Daily dermal exposure is calculated:

Daily dermal exposure = Unit exposure  x  Application rate  x  Area
Treated

          (mg/day)                    (mg/ lb ai)          (lb ai/ ft3) 
          (ft3/day)

Where:

Unit exposure =	normalized exposure value (mg exposure per pound ai
handled) derived from exposure study (MRID 43716501) (0.053 mg/lb ai)

Application rate =	normalized application rate (0.625 lb ai/ ft3)

Area treated =	normalized application area (690 ft3/day)

Absorbed Daily Dose is calculated:

Absorbed daily dermal dose = (Daily dermal exposure x absorption factor)
/ body weight

(mg/kg/day)                                     (mg/day)                
        (unitless)               (kg)

MOE Calculations for the Dermal Pathway:

The MOEs are calculated for each individual pathway using the MOE
formula:

MOE (unitless)  =   NOAEL / (Dose /BW)

Where:

NOAEL =	300 mg/kg/day (short-term)

Dose      =	0.011 mg/kg/day

BW	      =            70 kg (adult)	

≥ 100 are not of concern to HED for the residential population.

C.  Residential Postapplication Episodic Ingestion Exposure and Risk

The formula used to estimate residential postapplication episodic
(incidental) ingestion in this instance is based upon the assumption
that a toddler accidentally ingests an entire mothball.  In order to
assess the risk of this exposure route, a dose is estimated from
ingestion and compared to the incidental oral endpoint.  A potential
dose rate (PDR) is calculated using the ingestion rate (g/day)
multiplied by the fraction of ai in the mothball (unitless) and a
conversion factor (1000 mg/g).  For example, a mothball weighs 2.35
grams and contains 99.95% active ingredient.  Multiplying all the
factors together gives a PDR of 2349 mg/day.  The PDR is normalized by
body weight of the toddler (15 kg), which gives a value of 156.6 mg/day.
 The normalized PDR value is then used in conjunction with the endpoint
for incidental oral exposure (50 mg/kg/day) to give an MOE.  

The PDR value was calculated using the following equation:

PDR =	 IgR * F * CF1

PDR = 	2.35 g/day x 0.9995 x 1,000 mg/g

PDR = 	2349 mg/day

The PDRnorm value was then calculated using the following equation:  

PDRnorm = PDR / BW

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The MOEs for episodic ingestion are calculated for using the MOE
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Dose            =	156.6 mg/kg/day

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Page   PAGE  28  of   NUMPAGES  29 

