Document ID: EPA-HQ-OPP-2007-0937-0006
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-12-12T05:00Z

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

OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES

WASHINGTON, D.C. 20460

 September 28, 2007			

															

MEMORANDUM

Subject: 	Para Dichlorobenzene: Occupational and Residential Exposure
Assessment and Recommendations for the Reregistration Eligibility
Decision (RED). 

		[PC Codes 61501, DP Barcode D341252]

From:			Seyed Tadayon, Chemist

				Reregistration Branch 3

				Health Effects Division (7509P)

Through:		Catherine Eiden, Chief

				Reregistration Branch 3

				Health Effects Division (7509P)

		

To:			William Donovan, Chemist

				Reregistration Branch 3

				Health Effects Division (7509P)

	

  SEQ CHAPTER \h \r 1 This memo addresses residential and occupational
exposures and risks for the uses of para dichlorobenzene in indoor
applications.  

	

Executive Summery

Background and Purpose

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

Use Patterns and Formulations

	1, 4-Dichlorobenzene also referred to as para dichlorobenzene has a
benzene ring with two chlorine atoms attached at the 1 and 4 carbon
atoms. It is a white crystalline chemical with a penetrating,
camphoraceous odor.  The para dichlorobenzene that is found in indoor
air originates mainly from moth repellents used to protect clothing and
from deodorants that are used in the household.  

Para dichlorobenzene is used to control moths, molds, and mildew, and to
deodorize restrooms and waste containers. At room temperature, Para
dichlorobenzene is a white solid with a strong, pungent odor. When
exposed to air, it slowly changes from a solid to a vapor. It is the
vapor that acts as a deodorizer or insect killer. Most people recognize
the odor as the smell of mothballs, and can smell Para dichlorobenzene
in the air at very low levels. It also has applications in fumigants,
insecticides, lacquers, paints, and seed disinfection products.  This
assessment only concentrates on the indoor uses of para dichlorobenzene.
 All outdoor uses of para dichlorobenzene have been voluntarily
cancelled. 

Hazard Identification

Para dichlorobenzene is of low to moderate acute toxicity (i.e. Tox
category III or II) for oral and eye irritation exposures and is of low
toxicity (i.e. toxicity category III and IV) for skin and inhalation
exposures.  Para dichlorobenzene is not a dermal sensitizer.		

		This risk assessment incorporates the toxicological endpoints of
concern for Para dichlorobenzene as presented in the Hazard
Identification and Toxicity Endpoint Selection document of May 11, 2007.
 The endpoints are listed below:    

The short-term inhalation endpoint of concern was obtained from a 28-day
inhalation toxicity study in dogs.  The NOAEL (180 mg/ m3 or 150 PPM) is
based on decreased body weight and food consumption, hematological and
clinical chemistry changes and increased absolute and relative liver
weight.  The LOAEL was 500 PPM.  

The intermediate-term inhalation endpoint of concern was obtained from a
13 -week inhalation toxicity study in mouse.  The NOAEL (59 mg/ m3 or 55
PPM) is based on hematological changes seen at the next higher dose. The
LOAEL was 120 PPM.

The long-term inhalation endpoint of concern was obtained from a
published literature source (Combined Chronic Inhalation Toxicity/
Oncogenicity – Rat (S. Aiso et. al., 2005b)).  The selected NOAEL (3.4
mg/ m3 or 20 PPM) is based on increased incidences and severity of nasal
lesions and changes to the olfactory epithelium seen in females. The
LOAEL was 75 PPM.

The incidental short-term oral endpoint is selected from a 4 –week dog
feeding study.  The NOAEL (25 mg/kg/day) is based on increased liver
weight in males and increased alkaline phosphatase and liver weights and
gastrointestinal tract irritation in females seen at the next higher
dose, LOAEL, of 75 mg/kg/day.  No intermediate or long- term incidental
oral assessment is expected and therefore no endpoints for these
exposure scenarios were selected.

The short- and intermediate-term dermal endpoint of concern was obtained
from a 28-day dermal toxicity study in rats.  The NOAEL (>300 mg/kg/day)
is based on no toxicity observed at the highest dose tested. The LOAEL
was >300 mg/kg/day. 

Cancer risk estimates resulting from exposures to para-dichlorobenzene
were calculated for homeowners handling mothballs and individuals living
in homes treated with mothballs and inhaling mothball vapors. A Lifetime
Average Daily Dose (LADD) is calculated and then multiplied by a slope
factor of 4x10-3(mg/m3)-1, which was calculated by the IRIS program
using the low dose linear extrapolation model, based on dose response
data for hepatic tumors in male and female mice exposed to
para-dichlorobenzene via inhalation.

HED notes that in estimating the cancer risk for dermal exposures of
homeowners handling mothballs, we are comparing dermal exposures to
inhalation endpoints. The team decided to assess cancer risks for dermal
exposures using an inhalation endpoint since systemic effects (liver
tumors) were noted in the inhalation studies for para-dichlorobenzene.
The slope factor is based on these systemic effects. If the toxic
effects after inhalation exposures were localized (nose only) and not
systemic, it would not be appropriate to include a cancer risk for
dermal exposures that relied upon a toxic endpoint for localized effects
resulting from inhalation exposures.  

The Agency’s level of concern for risks (i.e., target level for MOEs
or Margins of Exposure) is defined by the uncertainty factors that are
applied to the assessment In general the Agency applies a factor of 10
to account for inter-species extrapolation to humans from the animal
test species and another factor of 10 to account for intra-species
sensitivity. The total uncertainty factors that have been applied to
Para dichlorobenzene residential risk assessments are 100 for short
-term dermal and incidental oral exposures, and 30 for short,
intermediate and long - term inhalation exposures. An Uncertainty Factor
(UF) of 30 was used to account for both interspecies extrapolation (3X),
and intraspecies variations (10X).  Traditionally, the uncertainty
factor for interspecies extrapolation is 10X.  The 10X is often
considered to be made up of two components, each equal to a half-log
value (3.16 for pharmacokinetics – how a chemical gets to the target
tissue, and 3.16 for pharmacodynamics – how the target tissue responds
to the chemical).  A full interspecies factor of 10X was not used in
this case because the RfC methodology developed by EPA was applied to
inhalation endpoint (EPA, 1994) in which dosimetry adjustments were used
to derive a NOAEL (HEC), , which accounts for the pharmacokinetic
component of the UF for interspecies extrapolation, thus allowing a
reduction of the interspecies factor from 10X to 3X.  An uncertainty
factor of 100 has been applied to episodic oral risk assessment. 

	

Residential and Occupational Handler Risk Estimates

Short-term dermal exposures of residential handlers result in risk
estimates that are below the Agency’s level of concern (i.e., MOE
>100).    

Estimated cancer risks for dermal exposures of handlers are below
OPP’s levels of concern (i.e., risks are below 1 x 10-6. For the
residential handler cancer risk estimate, the assumption that adult
individuals are exposed annually for 50 years out of a 70 year lifetime
is considered highly conservative

	The only occupational use of para-dichlorobenzene arises from use in
empty beehives.  Exposure from this activity is expected to be no higher
than the handler (dermal)  exposures from the indoor residential use of
mothballs which was assessed.  Risk estimates for residential handler
exposures are protective of this occupational use and below levels of
concern. As a result, HED believes a separate risk assessment for
occupational exposures (handler) is not warranted and was not conducted
for para-dichlorobenzene. 

Residential and Occupational Post application Risk

	Residential postapplication r tc \l3 "4.2.1	Residential Postapplication
Exposure Scenarios isk assessments have been completed for inhalation
exposures resulting from breathing para-dichlorobenzene vapors from
mothballs for adults, as well as non-dietary oral exposures (i.e.,
incidental ingestion of mothballs) for toddlers.  Inhalation exposures
are anticipated to be short-term, intermediate-term, and long-term in
duration.  The potential for dermal exposure is minimal, as indicated by
the risk calculations performed for residential handler exposure;
therefore, a dermal postapplication exposure assessment was not
conducted.
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	HED does not consider ingestion of mothballs to be a routine behavior
in which ingestion occurs on a regular basis, but instead considers this
an episodic event.  Accordingly, an assessment of episodic incidental
ingestion was performed.  As the short-term incidental oral NOAEL is 25
mg/kg/day, the short-term oral MOE for incidental ingestion of one
mothball by a toddler is 0.16 (compared to a target MOE of 100) and is,
therefore, of concern to HED.  HED performed additional calculations to
determine the dose level required to result in a MOE of 100.  Based on
these calculations, oral consumption of anything greater than 0.25
mg/kg/day para-dichlorobenzene results in a MOE less than 100 and is
considered a risk of concern by HED.  This oral dose of
para-dichlorobenzene, 0.25 mg/kg/day, is equivalent to a 15 kg toddler
consuming 0.16% of one 2.35 g mothball.  HED believes the risk estimate
for mothball ingestion is conservative as it is based on comparison of
an episodic (one-time event) to a toxic endpoint reflecting repeated
short-term exposures.

	Estimated cancer risks for dermal exposures of adults handling
mothballs during application are below HED’s levels of concern (risks
are below 1 x 10-6 using the linear approach).  For individuals living
in homes treated with mothballs and inhaling mothball vapors, the cancer
risk estimates could be as high as 6 x 10-5.  

	The only occupational use of para-dichlorobenzene arises from use in
empty beehives.  Exposure from this activity is expected to be no higher
than the post-application (inhalation) exposures from the indoor
residential use of mothballs which was assessed.  Risk estimates for
residential post-applcation exposures are protective of this
occupational use and below levels of concern. As a result, HED believes
a separate risk assessment for occupational exposures (post-application)
is not warranted and was not conducted for para-dichlorobenzene." 

Recommendations and DCI Rational

The registrant should conduct a confirmatory chamber study to determine
levels of para-dichlorobenzene in the air resulting from use of
mothballs at the maximum label rate.  The short-term post application
inhalation risk levels were estimated using surrogate exposure data from
a naphthalene mothball study.  However, para-dichlorobenzene has a
higher vapor pressure than naphthalene and the concentration of
para-dichlorobenzene in the air from mothball uses may exceed that of
naphthalene.  A targeted exposure study using para-dichlorobenzene
mothballs will ensure that the short-term inhalation exposures and risks
to para-dichlorobenzene as a result of mothball use have not been
underestimated.

1.0	Hazard Identification

1.1	Acute Toxicology Categories

The acute toxicity data for para dichlorobenzene is summarized in   SEQ
CHAPTER \h \r 1 Table 1.  Para dichlorobenzene are of low to moderate
acute toxicity (i.e. Tox category III or II) for oral and eye irritation
exposures and has low toxicity (i.e. toxicity category III and IV) for
skin and inhalation exposures.  Para dichlorobenzene is not dermal
sensitizer.	

Table   SEQ Table \* ARABIC  1  – Acute Toxicity of Para
Dichlorobenzene

Guideline

 No.	Study Type	Toxicity Category

870.1100	Acute Oral	III

870.1200	Acute Dermal 	III

870.1300	Acute Inhalation 	IV

870.2400	Primary Eye Irritation	II

870.2500	Primary Skin Irritation 	III

870.2600	Dermal Sensitization	NA

1.2	Toxicological Endpoints

	The endpoints that were used to assess exposures from residential
indoor applications are listed in Table 2.  

Table 2 – Endpoints Used for Assessing Residential Risks for Para
dichlorobenzene

Exposure

Scenario	Dose Used in Risk Assessment	Level of Concern (LOC) for Risk
Assessment	Study and Toxicological Effects

Incidental Oral Short-Term (1-30 days)	NOAEL=25 mg/kg/day	100	4-Week
oral toxicity study-dog  

NOAEL= 25 mg/kg/day

LOAEL=75 mg/kg/day, based on increased liver weight in males and
increased alkaline phosphatase and liver weight, irritation to GI tract
in females.

Dermal Short-Term (1-30 days)	NOAEL= > 300 mg/kg/day	100	21-day
dermal-rat NOAEL > 300 mg/kg/day (HDT) LOAEL = > 300 mg/kg/day.

Inhalation Short- Term (1-30 days)	NOAEL = 150 ppm or 

NOAELADJ= 180.36 mg/m3

	30	28-Day inhalation toxicity - dog 

Decreased body weight and food consumption, hematological and clinical
chemistry changes, increased absolute and relative liver weight, liver
histopathological changes, decreased absolute heart weight and absolute
and relative adrenal weights seen in both sexes at the next higher dose,
LOAEL, of 500 ppm. 

Inhalation Intermediate-Term (1-6 months)	NOAEL = 55 ppm

NOAELHEC = 58.92 mg/m3	30	13-Week Inhalation toxicity -mouse
hematological changes seen at the next higher dose, LOAEL, of 120 ppm. 

Inhalation- Chronic exposure (6-12 months)	NOAEL = 20 ppm 

HEC = 0.56 ppm or 3.4 mg/m3	30	Chronic Inhalation
Toxicity/carcinogenicity - rat (MRID N/A, open literature study, S. Aiso
et al., 2005b).

Olfactory epithelium changes observed at the next higher dose, NOAEL, of
75 ppm

Cancer (oral, dermal, inhalation)	Not Likely to be Carcinogenic to
Humans below doses that do not perturb normal liver homeostasis.

Based on the IRIS evaluation draft document of May 2006, the slope
factor linear approach was suggested.  “The recommended inhalation
risk unit for para-dichlorobenzene is 4x10-3(mg/m3)-1  , based on
hepatocellular tumors in male and female mice….”   Use of the low
dose extrapolation model would provide a worst case screening level
analysis.

1.3	Incident Report 

	An incident report prepared by the Chemistry and Exposure Branch (CEB)
of HED (D371997).

Incident report information for para-dichlorobenzene was gleaned from
the following sources:

1- Cases reported in the Poison Control Center (PCC) Database from 1993
to 2005.

2 - Cases reported in the Incident Data System (IDS) (Attachment 1) from
1999 to the present.

3 - Cases reported in the California Department of Pesticide Regulation
(CDPR) from 1999 to 2004. 

4 - Cases reported in the NIOSH system from 1998 to 2003.

The summary findings for the period 1993 to 2005 for
para-dichlorobenzene, mainly from PCC data are:

The proportion of symptomatic cases among those exposed in all
population groups evaluated (occupation, non-occupational, children)
were not significantly different from the overall, national composite
average.  Specifically, the proportion of symptoms among those followed
and the proportion hospitalizations among those seen at a health care
facility (HCF) is lower than the composite of all chemicals.  

Among children under the age of six, there were 3165 exposure cases to
para-dichlorobenzene while the entire population has 4480; children
represent the largest portion of the total exposed in the population,
70.6%. 

There was an average of about 344 exposures per year, 33 symptomatic
cases per year, and 38 cases per year seen in a heath care facility
across all population groups.

An irregular decreasing annual trend is evident in the 12 year-span of
data collected; the number of total exposed cases was reduced by half in
this period.

Although ratios for para-dichlorobenzene are below the composite
average, the number of exposures to children indicates that
opportunities for prevention exist and in order to prevent exposure,
actions restricting access to the active ingredient should be taken if
possible.  This could include special packaging and other limitations to
prevent children from reaching the active ingredient. 

Although the proportion of exposed children is actually less than the
composite of children exposed to ALL pesticides, given the potential
toxicity of the chemical, unknown long-term effects of exposure, and
ease of exposure to children given the usage profile (use of loose
mothballs in and around the home), additional public health protection
measures may be warranted.  These may include special packaging and
other limitations to block children from reaching the active ingredient
in addition to increased warning label language.

	

2.0	Summary of Use Patterns and Formulations

2.1 	Target Pests and Use Sites

	Para dichlorobenzene is registered as an insecticide and has been
widely used by the general population as a moth repellant to protect
garments from insect damage. It is also used for the control of lice and
ticks in and around bird cages, and for beetle proofing in dwellings. 
Usually, mothballs are expected to last for weeks or even months during
which para dichlorobenzene emits slowly as evidenced by the odor in the
room and the house where the mothball is located.  Para dichlorobenzene
is marketed in a variety of end-use products for homeowner use and an
occupational use (reg # 61671-2) for control of moths in beehives and
bee housing.  Since Para dichlorobenzene exposure is significantly
higher in mothballs, than the product used in bee housing, therefore,
this assessment will focus on para dichlorobenzene exposure from
mothballs only, and is considered a worst case scenario.  The exposure
from the remaining products containing para dichlorobenzene are not
expected to exceed that of mothballs.  Table 3 summarizes the technical
and manufacturing products.

Table 3 Para dichlorobenzene Technical and Manufacturing Products

Reg.No	%AI	Product Name	Use/Pest	Equipment	Max App Rate Qty	Max App Rate
Unit/Area

081433-00005	99.6	IMS MOTH CRYSTALS	HUMAN CLOTHING 

 

 

 

 

 

 

 

 

 	Product container

	9.96	lb 1K cu.ft

081433-00004	99.8	IMS MOTH CAKE

	0.0104	lb cu.ft

081433-00003	99.6	IMS MOTH BLOCK

	0.0104	lb cu.ft

081433-00002	99.8	IMS MOTHBALLS

	0.0104	lb cu.ft

070305-00003	100	PARA MOTHBALLS CEDAR SCENTED

	0.02	lb cu.ft

070305-00002	99.9	PARA MOTHBALLS CEDAR SCENTED

	0.02	lb cu.ft

070305-00001	99.5	PARA MOTHBALLS

	0.0199	lb cu.ft

010937-00001	99.9	AUSTIN'S MOTH CONTROL

	0.3122	lb bag

002915-00026	99.7	FULLER BRUSH CO. PERFUMED DEODORANT BLOCK

	0.0249	lb cu.ft

001475-00157	99.9	REEFER-GALLER NO-MOTH CLOSET HANGER

	0.0201	lb cu.ft

001475-00144	99.68	OLD FASHIONED LAVENDER SCENTED MOTH SACHETTES

	0.0208	lb cu.ft

001475-00143	99.68	MOTH-TEK PAPER COVERED MOTH BALL PACKETS

	35	packets 15 cu.ft

001475-00113	99.68	REEFER-GALLER NO-MOTH CLOSET HANGER

	0.0196	lb cu.ft

001475-00040	99.9	ENOZ MOTH CAKE VAPORIZER

	0.02	lb cu.ft

001475-00039	99.9	PARA MOTHBALLS CEDAR SCENTED

	19.98	lb 1K cu.ft

001475-00007	99.9	ENOZ 

ARADICHLOROBENZENE MOTH CAKE

	0.02	lb cu.ft

043576-00002	50	FEATHER GLO BIRD-CAGE-DEFENDER	BIRDS

0.0313	lb cage

002517-00022	50	DOUBLE DUTY BIRD GUARD

	1	container cage (L)

001903-00006	50	8 IN 1 BIRD PROTECTOR

	0.0234	lb cage

061671-00002	100	COLUMBIA PARA-DICHLOROBENZENE	BEEHIVES-EMPTY

0.1875	lb hive

058630-00003	98.6	VARPEL ROPE	INDOOR PREMISES	Rope applicator	9.86	ft 1K
cu.ft

3.0	Residential Handler Exposure and Risk

  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h \r 1 	The term “handler”
applies to individuals who mix, load, and apply the pesticide product. 
Only dermal exposures have been assessed for the residential handler
scenarios.  Inhalation exposure to residential handler is considered
minimal and therefore not assessed in this document. Handler exposures
occur during the application of mothballs using hand as a method of
application. Handler exposure durations are expected to be short-term
(1-30 days). Intermediate-term (1- 6 months) or long-term (> 6 months)
exposures are not expected for this particular use.  

3.1	Residential Handler Exposure Data

Naphthalene   SEQ CHAPTER \h \r 1 data (MRID# 437165-01) were used to
assess dermal exposures from hand applications.    

3.2	Residential Handler Exposure Assumptions

	The following assumptions were used in estimating risks resulting from
residential handler exposure to para dichlorobenzene:

The body weight of an adult handler is 70 kg;

The percent ai in the products ranges from 99.95- to 99.99 percent by
weight based upon the labels;

The master label rate of 0.02 lb ai/ft3 is applied to an indoor space;

The applicator treats 3 closets 600 ft3 (each closet measures 5 feet
width, 5 feet length and 8 feet height) in a day;

The applicator treats 3 dressers 90 ft3 (5 drawers per dresser and 6 ft3
per drawer) in a day. 

Unit Exposure Data

	      MRID # 437165-01- a study titled “Estimation of Homeowner
Exposure to LX1298-01 

(Naphthalene) resulting from Simulated Residential Use as an Insect
Repellent” was submitted in support

of naphthalene reregistration.  This study was used to estimate handler
dermal exposure to Para

dichlorobenzene.  

	Study Summary: The purpose of this study was to estimate the potential
for dermal exposure to the homeowner’s hands during application of
naphthalene. 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 test product was applied at a target application rate of 1.0 lb
ai/50 ft3 which is similar to the application rates used for p DCB.  
The person weighing out the mothballs and placing them in the closet and
dresser drawer at each location was monitored for dermal exposure of
naphthalene to the hands. Three trials were conducted in and near
Valdosta, Georgia.

		Three residences of similar design were utilized in the study. Each
residence was a single story, three bedroom, residence ranging in size
from approximately 1,800 to 2,400 ft2.  The temperature was controlled
at each site using central heating and air- conditioning. Each test site
was set up in a similar manner, with a rectangular shaped bedroom with
only one entrance and a single closet that only opened into the subject
bedroom, containing one bed and at least one set of dresser drawers. 

There was one applicator replicate per test site for a total of 3
applicator dermal (hand) exposure

replicates. The exact duration of each application was not provided in
the study.  The applicator replicates would weigh the mothballs and put
them into a container during placement and use in their respective
locations. After placement, the applicator would close the door(s) to
the closet and the dresser drawer and then exit the room.

For the applicator exposure cotton gloves were used to determine dermal
exposure as the

mothballs were placed in the treated zones. Table 4 provides a summary
of the applicator hand exposure as mg/lb ai.  The overall average
naphthalene hand exposure for three test sites, was 0.053 mg/lb ai
handled.  

Table 4.	Applicator Hand Exposure 

Trial	

Naphthalene Residue - Both Hands (mg)

92-298-01-21H-02	0.00807

92-298-01-21H-03	0.104

92-298-01-21H-04	0.0465

Mean	0.053

3.3	Non Cancer Residential Handler Risk Estimates

	The short-term dermal risk estimates (i.e. MOEs) for residential
handlers are presented in Table 5.  Handler MOEs are greater than 100
and therefore are not of concern.

Table 5 – Residential Handler Short-Term Risk Estimates for Dermal
Exposures 

Use Scenario	Area Treated

FT3	Application Rate lbai/FT3	Dermal

Unit Exposure

mg/lb ai	Dermal Dose mg/kg/day	Dermal MOE*

Handler Exposures from Mothball Application

Closets

Drawer	600

90	0.02

0.02	0.053

0.053	0.0091

0.00134	33,000

224,000

*All of the MOEs were greater than 100 and therefore are not of concern.

Dermal MOE = Short-term NOAEL (300 mg/kg/day) / dermal daily dose
(mg/kg/day)

Where, dermal dose = daily unit exposure (mg/lb ai) x application rate x
area treated / body weight (70 kg adult).

3.4 	NonCancer Residential Handler Risk Characterization

          There were no chemical specific data addressing
hand-application for indoor mothballs.  The exposures for the
hand-application exposure scenarios were based on surrogate data from a
naphthalene mothball application study in a closet and a dresser drawer.
 Use of a dermal unit exposure from application to an enclosed area
(i.e., closet or drawer) for indoor applications is appropriate for this
scenario.  The estimates for mothball application are based on very
limited data from a single study in which only 3 reliable replicates
were available and therefore exposure estimates are of low confidence.	

3.5    Non Cancer Occupational Handler Risk 

           The only occupational use of para-dichlorobenzene arises from
use in empty beehives.  Exposure from this activity is expected to be no
higher than the handler (dermal) exposures from the indoor residential
use of mothballs which was assessed.  Risk estimates for residential
handler exposures are protective of this occupational use and below
levels of concern. As a result, HED believes a separate risk assessment
for occupational exposures (handler) is not warranted and was not
conducted for para-dichlorobenzene.  

 

4.0 	Non Cancer Residential Post Application Exposures and Risks

	  The term “post-application” describes individuals who are exposed
to pesticides after entering areas previously treated with pesticides. 
Para dichlorobenzene post application inhalation exposures may occur
after applications of para dichlorobenzene are made to residential areas
such as closets and dresser drawers.  Dermal exposures were not assessed
because no dermal contact is expected after a complete sublimation
(dissipation) of para dichlorobenzene mothballs.  The following post
application scenarios were assessed for individuals accessing areas
treated with mothballs:

1)	Adult inhalation exposure resulting from mothball application;

2)   Children episodic mothball ingestion.  

4.1	Post Application Exposure Data

	No chemical specific post application data was submitted in support of
para dichlorobenzene re

registration.  Initially HED reviewed surrogate data from a study titled
“Estimation of Homeowner

Exposure to LX1298-01 (Naphthalene) Resulting from Simulated Residential
Use as an Insect Repellent”

MRID # 43716501, to assess para dichlorobenzene post application
exposure scenarios.  The Risk

Assessment Review Committee (RARC), 7/11/2007, recommended using
naphthalene data to assess short

term PDCB post application scenarios.  RARC also recommended using
published literature data to assess

intermediate and long-term post application inhalation scenarios.  

	For short –term post application exposure assessment HED used the
naphthalene study entitled “Estimation

of Homeowner Exposure to LX1298 01 (Naphthalene) MRID # 437165-01”
Resulting from Simulated Residential

Use as an Insect Repellent”. 

Three trials were conducted in and near Valdosta, Georgia. Three
residences of similar design were utilized in the study. Each residence
was a single story, three bedroom, residence ranging in size from
approximately 1,800 to 2,400 ft2.  The temperature was controlled at
each site using central heating and air-conditioning. Each test site was
set up in a similar manner, with a rectangular shaped bedroom with only
one entrance and a single closet that only opened into the subject
bedroom, containing one bed and at least one set of dresser drawers. 

For the first  trial , the treated bedroom measured approximately 154
ft2 with a closet of approximately 13.6 ft2.  A set of bi-fold doors was
used to close off the closet from the rest of the room. The bed was
located on the opposite wall approximately 6 ft from the closet door,
and the dresser was located on the wall adjacent to the wall with the
closet, approximately 6 ft from the closet door.  The non-treated room
was located approximately 40 ft from the treated room at the opposite
end of the residence.

For second trial, the treated bedroom measured approximately 106 ft2
with a closet of approximately 8.1 ft2.  A single solid door was used to
close off the closet from the rest of the room. The bed was located on
the opposite wall approximately 5.5 ft from the closet, and the dresser
was located on the wall adjacent to the wall with the closet,
approximately 2 ft from the closet door.  The non-treated room was
located approximately 30 ft from the treated room at the opposite end of
the residence.

For the third , the treated bedroom measured approximately 143 ft2 with
a closet of approximately 8.8 ft2.  A single solid door was used to
close off the closet from the rest of the room. The bed was located on
an adjacent wall to the closet and was approximately 2 to 3 ft from the
closet door. The dresser was located approximately 6 to 7 ft from the
closet door and 4 to 5 ft from the bed. The non-treated room was located
approximately 30 ft from the treated room at the opposite end of the
residence.

For the post-application inhalation exposure portion of the study there
were seven 15-minute sampling intervals over a 12-hour period on Days 4,
5 and 6 after the application for a total of 21 replicates per test site
(63 total replicates for the study).  The indoor inhalation samples
collected from the sampling unit attached to the person who entered the
room were used to simulate a homeowner who would normally enter the
bedroom on a regular basis during the day.

For the post-application air monitoring, at each test site there was one
stationary air sampler located in the closet and one inside the treated
dresser drawer.  The stationary air samplers in the treated zones
(closet and drawer) were run for three 15-minute intervals during the
same 12-hour period as the post-application inhalation exposure
monitoring on Days 4, 5 and 6 after the application. This resulted in
three closet replicates and three drawer replicates per sampling day for
a total 9 closet air replicates and 9 drawer replicates for each test
site (total of 27 closet air replicates and 27 drawer replicates for the
study). 

Also for the post-application air monitoring, there were three
stationary air samplers located within the room (one outside the closet
door, one on top of the dresser and one at the head of the bed). The
stationary air samplers outside the treated zones but inside the room
were run continuously and samples were collected at each 8-hour interval
for Days 4, 5 and 6 after the application resulting in three outside
closet replicates, three dresser top replicates and three bed replicates
per sampling day for a total of 27 room replicates per test site and 81
post-application stationary room air replicates for the study.

 

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 6.  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 7.

Table 6. Post-Application Inhalation Exposure (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 7.  Postapplication Air Concentration of Naphthalene (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

Arithmetic  Mean	0.66 mg/m3

		For intermediate and long-term post application exposure assessment,
HED used studies

conducted by EPA entitled “Total Exposure Assessment Methodology
(TEAM)”.  The TEAM studies

measured exposures to 20-25Volatile Organic Compounds (VOCs) in the air,
drinking water, and exhaled

breath of 650 persons in 4 states. These studies also measured indoor
residential concentrations of 1, 4

dichlorobenzene. 

	The (TEAM) studies were conducted in 1984 and 1987 in and around Los
Angeles and 

Contra Costa county.  These studies dealt with VOCs, carbon monoxide,
pesticides, and particles, often comparing indoor and outdoor exposures
to these contaminants at the same geographical location and within the
same households. In the early studies, exhaled breath and
shoulder-mounted monitors were used to measure personal-air exposures to
VOCs in the study subjects. These studies revealed the role of various
human activities in bringing individuals into contact with chemicals
indoors.  Mean indoor para dichlorobenzene concentrations measured in
the TEAM studies during the winter ranged from 20.2 to 36.2µg/m3, and
90th percentile values ranged from 68 to159µg/m3. During the summer,
para dichlorobenzene concentrations were considerably lower with means
ranging from 4.0 to 13.8 µg/m3, and 90th percentile values from 7.84 to
23.0µg/m3.

The most recent California study was conducted in Woodland, California,
in the spring of 1990.The mean concentration of 1, 4 -dichlorobenzene in
125 samples was 16 µg/m3, with a range from below the quantifiable
limit of 0.26 µg/m3 to 300 µg/m3. The mean from the springtime study
lies between the summer and winter means measured in the earlier TEAM
studies

The data indicate a seasonal dependence of the para dichlorobenzene
levels.  HED used maximum mean concentration of 36.2ug/m3 (winter value)
to assess short-term and intermediate- term scenarios.  For long-term
and cancer assessments, HED used an average of the seasonal value
(21ug/m3).

	Review of Human Research

This risk assessment relies in part on data from studies in which adult
human subjects were exposed (either intentionally or unintentionally) to
a pesticide or other chemical.  These studies have been determined to
require a review of their ethical conduct, and have received that
review.  It was concluded that there are no regulatory barriers to
EPA’s reliance on these studies in its actions under FIFRA (J.M.
Carley, 4/24/2007 & J.M. Carley, 9/27/2007).

4.2 Non Cancer Residential Post Application Exposure Assumptions

Assumptions

Label recommended application rate of 0.02 lb ai/50 ft3;

One mothballs weighs 2.35 grams;

For short and intermediate-term exposure maximum mean concentration of
36.2 ug/m3 was used;

For long-term exposure average concentration of 21ug/m3 was used.  This
value was calculated by assuming the fall and spring values are the
same.  Therefore average long -term concentration is equal to [(winter
36 ug/m3) + (summer 14 ug/m3) + (spring 16 ug/m3) + (fall 16 ug/m3)] /4.

Inhalation assessment was only conducted for adults, as these risk
values are protective for children. .  Adult and toddler inhalation
exposure estimates are the same because endpoints derived from the
inhalation toxicity studies (all durations) were adjusted for
pharmacokinetic (PK) differences when NOAEL Human Equivalent
Concentrations (HEC) were calculated.  

As no acute endpoint was selected, HED used the short-term incidental
oral endpoint of 25 mg/kg/day to estimate risk from episodic ingestion
of one mothball.  

4.3 Non Cancer Post Application Exposure and Risk Estimates

	The exposure and risk estimates for the residential post application
scenarios are presented in Table 8. All of the MOEs for post-application
inhalation exposures, regardless of duration, exceed the target MOE of
30, and are not of concern.  The risk estimate for episodic ingestion of
mothballs results in a MOE < 100 and therefore is of concern.  The only
occupational use of para-dichlorobenzene arises from use in empty
beehives.  Exposure from this activity is expected to be no higher than
the post-application (inhalation) exposures from the indoor residential
use of mothballs which was assessed.  Risk estimates for residential
post-application exposures are protective of this occupational use and
below levels of concern. As a result, HED believes a separate risk
assessment for occupational exposures (post-application) is not
warranted and was not conducted for para-dichlorobenzene.

Episodic Ingestion Risk Estimate

	Toddler episodic (incidental) ingestion of one para dichlorobenzene
mothball results in an MOE < 100 and, therefore, is of concern to HED. 
An oral dose of 0.25 mg/kg/day would be required to result in an MOE =
100.  This dose is equivalent to toddler incidental ingestion of 0.16%
of one mothball (3.75 mg of 2350 mg). HED believes the risk estimate for
mothball ingestion is conservative and likely to overestimate risk as it
is based on comparison of an episodic (one-time event) to a toxic
endpoint reflecting repeated short-term exposures.

Although the data from the National Health and Nutrition Examination
Survey (NHANES) studies were not directly used in the present risk
assessment, HED compared the levels of risk reported in NHANES to those
obtained from the TEAM studies. Acknowledging the inherent uncertainties
involved in extrapolating 2,5-dichlorophenol levels in urine (creatinine
corrected) samples to levels of para-dichlorobenzene in the air, it is
noteworthy that the geometric mean value obtained from the 1999-2000
survey years for individuals age 6 and older converts to an air
concentration of 16 ug/m3 para-dichlorobenzene.  This level is quite
similar to the average seasonal value of 21 ug/m3 used for the long-term
inhalation exposure analysis reported in Table 8, and provides
additional confidence in the levels used to assess long-term exposures
to para-dichlorobenzene.

 Table 8 – Para dichlorobenzene Non Cancer Residential Post
Application Risk Estimates

Source of exposure	Exposed Population	MOE*

Inhalation Short –Term 

Mothballs 	Adult(Accessing Treated Areas)	212

	Adult(Inhabiting Treated Home)	273

Inhalation Intermediate –Term 

Mothballs	Adult	1650

Inhalation Long- –Term 

Mothballs	Adult	160

	Episodic mothball Ingestion 

	Mothballs	Toddler	<1

Short-term inhalation risk = NOAEL of 180.36 mg/m3/mean air
concentration (from Naphthalene study MRID #437165-01) 0.85 mg/m3 for
accessing treated areas or 0.66 mg/m3 for inhabiting treated areas; 

Intermediate-term inhalation risk = NOAEL of 58.92 mg/m3/ mean air
concentration from TEAM study 36 ug/m3;

Long-term inhalation risk =NOAEL of 3.4 mg/m3/ mean air concentration
from TEAM study 21 ug/m3;

Episodic mothball ingestion oral dose to child (1-6 year old) =
[Mothballs ingestion rate (2.35 g/day) x Fraction of ai of mothball
formulations (99.5%) x 1,000 mg/g] / bw (15 kg);

Episodic mothball ingestion risk = NOAEL (25 mg/kg/day) for short-term
assessments)/155.8 (mg/kg/day) oral dose.

4.4 	Para dichlorobenzene Cancer Risk Assessment

	

Cancer risk estimates resulting from exposures to para-dichlorobenzene
were calculated for homeowners handling mothballs and individuals living
in homes treated with mothballs and inhaling mothball vapors. A Lifetime
Average Daily Dose (LADD) is calculated and then multiplied by a slope
factor of 4x10-3(mg/m3)-1, which was calculated by IRIS using lowdose
linear extrapolation, based on dose response data for hepatic tumors in
male and female mice exposed to para-dichlorobenzene via inhalation. The
estimates of cancer risk are based on the assumption of low dose
linearity (presented in Tables 9 and 10) and range the upper bounds on
cancer risk from 7.1 x 10-9 for dermal exposure during the application
of mothballs to 6.0 x 10-5 for post-application inhalation exposure to
mothballs.

HED notes that in estimating the cancer risk for dermal exposures of
homeowners handling mothballs, we are comparing dermal exposures to
inhalation endpoints. The team decided to assess cancer risks for dermal
exposures using an inhalation endpoint since systemic effects (liver
tumors) were noted in the inhalation studies for para-dichlorobenzene.
The slope factor is based on these systemic effects. If the toxic
effects after inhalation exposures were localized (nose only) and not
systemic, it would not be appropriate to include a cancer risk for
dermal exposures that relied upon a toxic endpoint for localized effects
resulting from inhalation exposures.  

Handler Cancer Risk Calculation 

For the residential handler cancer risk estimate, a highly conservative
assumption that adult individuals are exposed annually for 50 years out
of a 70 year lifetime was used. In addition, the cancer risk estimates
are conservative because the LADD calculated for dermal exposures do not
include a dermal absorption factor, that is, 100% dermal absorption has
been assumed. 

Estimated para-dichlorobenzene cancer risks for dermal exposures of
handlers are presented below in Table 9. Cancer risk estimates are below
1 x 10-6 using the slope factor approach.  

Table 9 Estimated para-Dichlorobenzene Cancer Risks for Adults During
Mothball Application (Dermal Exposures)

Application Method	

Exposed Individual	

Location	Dermal Average Daily Dose (mg/kg/day)	

LADD (mg/kg/day)	

Upper Bound on Cancer Risk Estimate  

Hand	Adult	Closet	0.0091	3.55e-5	4.9e-8

Drawer	0.00134	5.20e-6	7.1e-9

Average daily Dermal dose = daily unit exposure (mg/lb ai) x application
rate x amount handled per day / body weight (70 kg adult (mg/day) LADD =
  Daily Dose (Dermal Dose) (mg/kg/day) * 2 days/365 * 50/70 (50 years
handler exposure; 70 years lifetime assumption)

Cancer Risk = LADD * slope factor (1.4e-3 mg/kg/day)

The slope factor  4x10-3(mg/m3)-1) was converted to 1.4 e-3 mg/kg/day. 
It was assumed that the breathing rate for an adult is 1 m3/h (24 hrs a
day) and the body weight is 70 kg. 

Post application Cancer Risk Calculation 

	Estimated para-dichlorobenzene cancer risks for post application
inhalation exposures are presented below in Table 10.

Table 10  para-Dichlorobenzene Post Application Cancer Risk Assessment
for Inhalation Exposures

Exposed Individual	Inhalation Average Daily Dose (ug/m3)	

LADD (ug/m3)	Upper Bound on Cancer Risk Estimate  

Adult	21	15	6.0e-5

LADD = Daily Dose (Inhalation Dose) (ug/m3) * 50/70 (50 years homeowner
exposure; 70 years lifetime assumption)

Cancer Risk = LADD * slope factor (4x10--3(mg/m3)-1)

	Using linear low dose extrapolation and a slope factor of 4.0x10-3
(mg/m3)-1 the cancer risk estimates could be as high as 6 x 10-5.  For
the residential post-application cancer risk estimate, a highly
conservative assumption that homeowners are exposed annually for 50
years out of a 70 year lifetime was used.

The linear low dose extrapolation model provides a range of cancer
risks.  As with all linear low dose extrapolation models, the range is
bracketed by an upper bound and a lower bound on these risks.  The 6 x
10-5 cancer risk estimate represents an upper bound on cancer risk for
exposures to para-dichlorobenzene but the cancer risk could be as low as
zero.  This is independent of the strengths and weaknesses of the cancer
data. HED believes that the carcinogenic risks are below the upper bound
and may be closer to zero for para-dichlorobenzene for several reasons
as follows.  Available evidence as described  above in Section 3.4.9
(Classification of Carcinogenic Potential) of this document, indicates
that the mechanism leading to tumor formation in the livers of mice
after exposure to para-dichlorobenzene is based on sustained mitogenic
stimulation and proliferation of hepatocytes.  This information forms
the basis of a plausible mode of action for tumorigenesis in the mice
livers.  In addition, the BMCL 10 for hepatocellular adenoma or
carcinoma formation in female mice is 22.9 mg/m3 (IRIS Program, 2006). 
If the BMCL 10 is compared to the measured concentrations of
para-dichlorobenzene in people’s homes (0.021 mg/ m3), the BMCL 10 is
1000 times higher than actual exposures. That is, there is a 1000-fold
margin of safety between the dose at which there is a 10% tumor response
in test animals, at the lowest measurable incidence, and actual measured
exposure in people’s homes.  Consequently, HED believes the
carcinogenic risk from this use is not of concern for the following
reasons: 1) there is mechanistic data to support a lower cancer risk
estimate based on a mitogenic mode of carcinogenic action, 2)
conservatisms in the exposure estimates, and 3) a large margin of safety
between estimated human exposure and the point at which there is a
measurable (10%) tumor response.

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