**UNITED STATES ENVIRONMENTAL PROTECTION
AGENCY**![](media/image1.png){width="1.09375in"
height="0.8729166666666667in"}

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

May 7, 2008

**[MEMORANDUM]{.underline}**

SUBJECT: **Naphthalene**: Phase 2 Amendment: Revisions Required to
Update Hazard Characterization.

  ----------------------------------- -----------------------------------
  **PC Code:** 055801                 **DP Barcode:** 352389

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

  **Petition No.:** N/A               **Regulatory Action:** Phase 2

  **Risk Assessment Type:** Response  **Case No.:** 0022
  to Error Only Comments              

  T**XR 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 revision of the April 10, 2008 naphthalene
occupational and residential exposure assessment chapter, "Phase 2
Amendment: Response to Registrant Submitted Error Only Comments in
Reference to "Naphthalene: Occupational and Residential Exposure
Assessment and Recommendations for the Reregistration Eligibility
Decision Document." An update of this chapter is required to address the
following hazard characterization language:

-   Executive Summary, Residential Indoor Postapplication Noncancer
    Exposure and Risk Estimates, Second Paragraph has been revised to
    read:

> Since the data available to date indicate that rodents are more likely
> to be susceptible to the respiratory effects of naphthalene than
> humans, the use of rodents as a model without application of species
> scaling accounting for species differences in dosimetry and metabolism
> would likely result in inaccurate estimates of human risk. Therefore,
> 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.

-   1.2 Toxicological Endpoints, Second Paragraph has been revised to
    read:

> 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 2 Amendment: Response to Registrant
> Submitted Error Only Comments in Reference to "Naphthalene: HED
> Chapter of the Reregistration Eligibility Decision Document (RED),"
> (D. Drew, D335941).

-   1.2 Toxicological Endpoints, descriptor following Table 2.
    Toxicological Doses and Endpoints for Naphthalene for Use in Human
    Health Risk Assessments has been revised to read:

> \* Since the data available to date indicate that rodents are more
> likely to be susceptible to the respiratory effects of naphthalene
> than humans, the use of rodents as a model without application of
> species scaling accounting for species differences in dosimetry and
> metabolism would likely result in inaccurate estimates of human risk..
> Therefore, 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).

-   2.2.1 Residential Postapplication Inhalation Exposure and Risk,
    Second Paragraph has been revised to read:

> Since the data available to date indicate that rodents are more
> susceptible to the respiratory toxicity of naphthalene, the use of
> rodents as a model without the appropriate species scaling accounting
> for species differences in dosimetry would likely result in an
> inaccurate estimation of human risk. Therefore, 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.

**Table of Contents**

[**Executive Summary** 4](#__RefHeading___Toc192045115)

[**1.0** **Background Information** 4](#__RefHeading___Toc192045116)

[**1.1** **Purpose and Criteria for Conducting Exposure Assessments**
4](#__RefHeading___Toc192045117)

[**1.2 Toxicological Endpoints** 4](#__RefHeading___Toc192045118)

[**1.3 Incident Report** 4](#__RefHeading___Toc192045119)

[**1.4** **Summary of Use Patterns, Formulations, and Application
Methods** 4](#__RefHeading___Toc192045120)

[**2.0** **Residential Exposure and Risk**
4](#__RefHeading___Toc192045121)

[**2.1 Residential Handler Noncancer Exposure and Risk**
4](#__RefHeading___Toc192045122)

[**2.1.1** **Residential Handler Noncancer Exposure and Risk Estimates**
4](#__RefHeading___Toc192045123)

[**2.1.2** **Residential Handler Cancer Exposure and Risk**
4](#__RefHeading___Toc192045124)

[**2.2** **Residential Postapplication Exposure and Risks**
4](#__RefHeading___Toc192045125)

[**2.2.1 Residential Postapplication Inhalation Exposure and Risk**
4](#__RefHeading___Toc192045126)

[**2.2.2** **Residential Postapplication Inhalation Exposure and Risk
Estimates** 4](#__RefHeading___Toc192045127)

[**2.2.3** **Residential Postapplication Cancer Exposure and Risk**
4](#__RefHeading___Toc192045128)

[**2.2.4 Residential Postapplication Episodic Ingestion Exposure and
Risk** 4](#__RefHeading___Toc192045129)

[**2.2.5** **Residential Postapplication Episodic Ingestion Exposure and
Risk
Estimates**.......................................................................................4](#__RefHeading___Toc192045130)

[**References** 4](#__RefHeading___Toc192045131)

[**APPENDIX A** 4](#__RefHeading___Toc192045132)

[**A. Introduction** 4](#__RefHeading___Toc192045133)

[**B. Residential Applicator Exposure and Risk**
4](#__RefHeading___Toc192045134)

[**C. Residential Postapplication Episodic Ingestion Exposure and Risk**
4](#__RefHeading___Toc192045135)

[]{#__RefHeading___Toc192045115 .anchor}**Executive Summary**

**Background and Purpose**

Number range CHAPTERThis 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 and risk 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.

**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.

Since the data available to date indicate that rodents are more likely
to be susceptible to the respiratory effects of naphthalene than humans,
the use of rodents as a model without application of species scaling
accounting for species differences in dosimetry and metabolism would
likely result in inaccurate estimates of human risk. Therefore, 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.

Comparisons for acute and short-term exposure durations were estimated
using standard assumptions and the results of the aforementioned
exposure study (MRID 43716501). Inhalation exposure data from the study
applies 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).
Based upon direct comparison, 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) and are 20X and 30X below the animal dose (NOAEL),
respectively.

A direct comparison of intermediate- and long-term exposure durations
was also performed using standard assumptions; however, due to 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. For the purposes of this risk
assessment, only those results which pertain to the indoor ambient
concentrations of naphthalene were used estimate postapplication
inhalation (intermediate- and long-term) 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). A NOAEL was not identified for
long-term inhalation exposure and, therefore, this duration was not
assessed.

**Residential Indoor Postapplication Cancer Risk Estimates**

Residential handler cancer exposure and risk estimates were not assessed
due to the uncertainty of whether naphthalene poses a human cancer
concern at ambient or environmental levels of exposure because of
potential species differences in rates of metabolism leading to its
toxicity.

**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.

Toddler episodic 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 episodic (incidental) ingestion of 0.32% of one
mothball (7.5 of 2350 total mg).

**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).

1.  []{#__RefHeading___Toc192045116 .anchor}**Background Information**

    1.  []{#__RefHeading___Toc192045117 .anchor}**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.

[]{#__RefHeading___Toc192045118 .anchor}**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.

+---------+------------------+---------+---------------------+--------+
| **T     |                  |         |                     |        |
| able 1. |                  |         |                     |        |
| Acute   |                  |         |                     |        |
| T       |                  |         |                     |        |
| oxicity |                  |         |                     |        |
| of      |                  |         |                     |        |
| Naphth  |                  |         |                     |        |
| alene** |                  |         |                     |        |
+=========+==================+=========+=====================+========+
| *       | **Study Type**   | *       | **Results**         | *      |
| *GDLN** |                  | *MRID** |                     | *Tox** |
|         |                  |         |                     |        |
|         |                  |         |                     | **Cate |
|         |                  |         |                     | gory** |
+---------+------------------+---------+---------------------+--------+
| 870.11  | Acute Oral - rat | 257224  | LD~50~: 2649 mg/kg  | III    |
|         |                  |         | (♂+♀)               |        |
+---------+------------------+---------+---------------------+--------+
| 870.12  | Acute Dermal     | 257229  | LD~50~ \>2000 mg/kg | III    |
|         |                  |         | (♂+♀)               |        |
+---------+------------------+---------+---------------------+--------+
| 870.13  | Acute Inhalation | 257902  | LC~50~ \> 0.4 mg/L  | II     |
|         |                  |         | (77.7 ppm) (♂+♀)    |        |
+---------+------------------+---------+---------------------+--------+
| 870.24  | Primary Eye      | 257228  | Slight-moderate     | III    |
|         | Irritation       |         | irritation          |        |
+---------+------------------+---------+---------------------+--------+
| 870.25  | Primary Skin     | 257227  | Moderate irritation | III    |
|         | Irritation       |         |                     |        |
+---------+------------------+---------+---------------------+--------+
| 870.26  | Dermal           | 0       | Nonsensitizer --    | N/A    |
|         | Sensitization    | 0148173 | guinea pig          |        |
+---------+------------------+---------+---------------------+--------+

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 2 Amendment: Response to Registrant
Submitted Error Only Comments in Reference to "Naphthalene: HED Chapter
of the Reregistration Eligibility Decision Document (RED)," (D. Drew,
D335941).

+---------+--------+-----------+-----------+--------------------------+
| **Table |        |           |           |                          |
| 2.      |        |           |           |                          |
| Toxico  |        |           |           |                          |
| logical |        |           |           |                          |
| Doses   |        |           |           |                          |
| and     |        |           |           |                          |
| En      |        |           |           |                          |
| dpoints |        |           |           |                          |
| for     |        |           |           |                          |
| Naph    |        |           |           |                          |
| thalene |        |           |           |                          |
| for Use |        |           |           |                          |
| in      |        |           |           |                          |
| Human   |        |           |           |                          |
| Health  |        |           |           |                          |
| Risk    |        |           |           |                          |
| Assess  |        |           |           |                          |
| ments** |        |           |           |                          |
+=========+========+===========+===========+==========================+
| **Expo  | *      | **Unc     | **Level   | **Study and              |
| sure/** | *Point | ertainty/ | of        | Toxicological Effects**  |
|         | of     | Safety    | Concern   |                          |
| **Sce   | Depar  | Factors** | for Risk  |                          |
| nario** | ture** |           | Ass       |                          |
|         |        |           | essment** |                          |
+---------+--------+-----------+-----------+--------------------------+
| **Inc   |        |           |           |                          |
| idental |        |           |           |                          |
| Oral    |        |           |           |                          |
| Ex      |        |           |           |                          |
| posures |        |           |           |                          |
| (Post   |        |           |           |                          |
| applica |        |           |           |                          |
| tion)** |        |           |           |                          |
+---------+--------+-----------+-----------+--------------------------+
| Inc     | NOAEL= | UF~A~=    | MOE= 100  | **NTP Developmental Rat  |
| idental | 50     | 10x       |           | Study**                  |
| Oral    |        |           |           |                          |
| (Shor   | mg/    | UF~H~=    |           | NOAEL = 50 mg/kg/day     |
| t-term) | kg/day | 10x       |           |                          |
|         |        |           |           | LOAEL= 150 mg/kg/day     |
|         |        |           |           | based on maternal        |
|         |        |           |           | effects -- persistent    |
|         |        |           |           | clinical signs of        |
|         |        |           |           | lethargy, slow           |
|         |        |           |           | breathing, rooting       |
|         |        |           |           | behavior, and            |
|         |        |           |           | significant decreases in |
|         |        |           |           | body weights/body weight |
|         |        |           |           | gains and decreased food |
|         |        |           |           | and water consumption.   |
+---------+--------+-----------+-----------+--------------------------+
| *       |        |           |           |                          |
| *Dermal |        |           |           |                          |
| Expo    |        |           |           |                          |
| sures** |        |           |           |                          |
+---------+--------+-----------+-----------+--------------------------+
| Dermal  | Dermal | UF~A~=    | MOE= 100  | **90-Day Dermal Toxicity |
| (Shor   | NOAEL= | 10x       |           | Study --Rat**            |
| t-Term) | 300    |           |           |                          |
|         | mg/    | UF~H~=    |           | NOAEL = 300 mg/kg/day    |
|         | kg/day | 10x       |           |                          |
|         |        |           |           | 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.                 |
+---------+--------+-----------+-----------+--------------------------+
| **Inh   |        |           |           |                          |
| alation |        |           |           |                          |
| Expo    |        |           |           |                          |
| sures** |        |           |           |                          |
+---------+--------+-----------+-----------+--------------------------+
| \*Inh   | Inha   | N/A       | N/A       | **4-Week (Nose-Only)     |
| alation | lation |           |           | Inhalation -- Rat**      |
| (Shor   |        |           |           |                          |
| t-term) | LOAEL  |           |           | NOAEL = 3 ppm            |
|         |        |           |           |                          |
|         | = 10   |           |           | LOAEL = 10 ppm based     |
|         | ppm or |           |           | increased incidence and  |
|         | 52     |           |           | severity of nasal        |
|         | m      |           |           | lesions (slight          |
|         | g/m^3^ |           |           | disorganization, rosette |
|         |        |           |           | formation, basal cell    |
|         | NOAEL  |           |           | hyperplasia, erosion,    |
|         |        |           |           | atrophy, and degenerate  |
|         | = 3    |           |           | cells in the olfactory   |
|         | ppm or |           |           | epithelium; loss of      |
|         |        |           |           | bowman's glands;         |
|         | 16     |           |           | respiratory epithelium   |
|         | m      |           |           | hypertrophy; rosette     |
|         | g/m^3^ |           |           | formation in the septal  |
|         |        |           |           | organ of Masera and      |
|         |        |           |           | fusion of the            |
|         |        |           |           | turbinates).             |
+---------+--------+-----------+-----------+--------------------------+
| \*Inh   | Inha   | N/A       | N/A       | **13-Week (nose-only)    |
| alation | lation |           |           | Inhalation Rat Study;    |
| (Inte   |        |           |           | Subchronic (nose-only)   |
| rmediat | LOAEL  |           |           | Neurotoxicity Rat        |
| e-term; |        |           |           | Study**                  |
| 1-6     | = 2    |           |           |                          |
| months) | ppm or |           |           | NOAEL = 1 ppm            |
|         | 10     |           |           | (Subchronic              |
|         | m      |           |           | neurotoxicity study)     |
|         | g/m^3^ |           |           |                          |
|         |        |           |           | NOAEL (13 week           |
|         | NOAEL  |           |           | inhalation study) -- not |
|         |        |           |           | identified.              |
|         | = 1    |           |           |                          |
|         | ppm or |           |           | LOAEL = 2 ppm (13 week   |
|         |        |           |           | inhalation study) based  |
|         | 5.2    |           |           | on increased incidence   |
|         | m      |           |           | and severity of nasal    |
|         | g/m^3^ |           |           | 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. |
+---------+--------+-----------+-----------+--------------------------+
| \*Inh   | Inha   | N/A       | N/A       | **NTP ChronicToxicity    |
| alation | lation |           |           | and Carcinogenicity      |
| (Lon    | LOAEL  |           |           | Studies in the Rat and   |
| g-term) |        |           |           | Mouse**                  |
|         | = 10   |           |           |                          |
|         | ppm or |           |           | NOAEL -- not identified. |
|         | 52     |           |           |                          |
|         | m      |           |           | LOAEL (rat study) = 10   |
|         | g/m^3^ |           |           | 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.              |
+---------+--------+-----------+-----------+--------------------------+
| > **All |        |           |           |                          |
| >       |        |           |           |                          |
|  Routes |        |           |           |                          |
| > of    |        |           |           |                          |
| > Exp   |        |           |           |                          |
| osure** |        |           |           |                          |
+---------+--------+-----------+-----------+--------------------------+
| Cancer  | >      |           |           |                          |
| (inha   | Cancer |           |           |                          |
| lation) | > was  |           |           |                          |
|         | > not  |           |           |                          |
|         | > as   |           |           |                          |
|         | sessed |           |           |                          |
|         | > due  |           |           |                          |
|         | > to   |           |           |                          |
|         | > the  |           |           |                          |
|         | >      |           |           |                          |
|         |  uncer |           |           |                          |
|         | tainty |           |           |                          |
|         | > of   |           |           |                          |
|         | > w    |           |           |                          |
|         | hether |           |           |                          |
|         | >      |           |           |                          |
|         |  napht |           |           |                          |
|         | halene |           |           |                          |
|         | >      |           |           |                          |
|         |  poses |           |           |                          |
|         | > a    |           |           |                          |
|         | >      |           |           |                          |
|         |  human |           |           |                          |
|         | >      |           |           |                          |
|         | cancer |           |           |                          |
|         | > c    |           |           |                          |
|         | oncern |           |           |                          |
|         | > at   |           |           |                          |
|         | > a    |           |           |                          |
|         | mbient |           |           |                          |
|         | > or   |           |           |                          |
|         | > e    |           |           |                          |
|         | nviron |           |           |                          |
|         | mental |           |           |                          |
|         | >      |           |           |                          |
|         | levels |           |           |                          |
|         | > of   |           |           |                          |
|         | > ex   |           |           |                          |
|         | posure |           |           |                          |
|         | > b    |           |           |                          |
|         | ecause |           |           |                          |
|         | > of   |           |           |                          |
|         | > pot  |           |           |                          |
|         | ential |           |           |                          |
|         | > s    |           |           |                          |
|         | pecies |           |           |                          |
|         | >      |           |           |                          |
|         |  diffe |           |           |                          |
|         | rences |           |           |                          |
|         | > in   |           |           |                          |
|         | >      |           |           |                          |
|         |  rates |           |           |                          |
|         | > of   |           |           |                          |
|         | > meta |           |           |                          |
|         | bolism |           |           |                          |
|         | > l    |           |           |                          |
|         | eading |           |           |                          |
|         | > to   |           |           |                          |
|         | > its  |           |           |                          |
|         | > tox  |           |           |                          |
|         | icity. |           |           |                          |
+---------+--------+-----------+-----------+--------------------------+

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.
UF~A~ = extrapolation from animal to human (interspecies). UF~H~ =
potential variation in sensitivity among members of the human population
(intraspecies). MOE = margin of exposure. LOC = level of concern. N/A =
not applicable.

\* Since the data available to date indicate that rodents are more
likely to be susceptible to the respiratory effects of naphthalene than
humans, the use of rodents as a model without application of species
scaling accounting for species differences in dosimetry and metabolism
would likely result in inaccurate estimates of human risk. Therefore,
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).

[]{#__RefHeading___Toc192045119 .anchor}**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.

4.  []{#__RefHeading___Toc192045120 .anchor}**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. Percent active ingredient of indoor-use products range from
99.7-100%, and from 7-99.9% 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        |            |         |     |                            |
| R         |            |         |     |                            |
| egistered |            |         |     |                            |
| Na        |            |         |     |                            |
| phthalene |            |         |     |                            |
| Uses**    |            |         |     |                            |
+===========+============+=========+=====+============================+
| **Indoor  |            |         |     |                            |
| Use**     |            |         |     |                            |
+-----------+------------+---------+-----+----------------------------+
| **        | **Use      | *       | **% | **App. Rate for the Area   |
| Product** | Site**     | *Formul | A.I | to be Treated**            |
|           |            | ation** | .** |                            |
+-----------+------------+---------+-----+----------------------------+
| ENOZ® Old | Indoor     | M       | 99  | 1 ounce per 3 ft^3^ -      |
| Fashioned | storage    | othball | .95 |                            |
| Mothballs | areas      |         |     | 0.25 lb ai / Average       |
|           | (          |         |     | Garment Bag (12 ft^3^)     |
| (1475-74) | containers |         |     |                            |
|           | and        |         |     | 0.33 lb ai / Large Trunk   |
|           | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| ENOZ® Old | Indoor     | Flake   | 99  | 1 ounce per 3 ft^3^ -      |
| Fashioned | storage    |         | .95 |                            |
| Moth      | areas      |         |     | 0.25 lb ai / Average       |
| Flakes    | (          |         |     | Garment Bag (12 ft^3^)     |
|           | containers |         |     |                            |
| (1475-75) | and        |         |     | 0.33 lb ai / Large Trunk   |
|           | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| ENOZ®     | Indoor     | M       | 99  | 1 ounce per 3 ft^3^ -      |
| Cedar     | storage    | othball | .85 |                            |
| Pine      | areas      |         |     | 0.25 lb ai / Average       |
| Mothballs | (          |         |     | Garment Bag (12 ft^3^)     |
|           | containers |         |     |                            |
| (         | and        |         |     | 0.33 lb ai / Large Trunk   |
| 1475-120) | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| Chaperone | Attics and | Flake   | 100 | 1 pound per 400 ft^3^      |
| Squirrel  | wall voids |         |     |                            |
| and Bat   | and indoor |         |     | 1 ounce per 3 ft^3^ -      |
| Repellant | storage    |         |     |                            |
|           | areas      |         |     | 0.25 lb ai / Average       |
| (         | (          |         |     | Garment Bag (12 ft^3^)     |
| 2724-685) | containers |         |     |                            |
|           | and        |         |     | 0.33 lb ai / Large Trunk   |
|           | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| Dr. T's   | Attics and | Flake   | 99  | 1 pound per 400 ft^3^      |
| Rabbit,   | wall voids |         | .95 |                            |
| Squirrel, |            |         |     |                            |
| Bat &     |            |         |     |                            |
| Bird      |            |         |     |                            |
| Repellant |            |         |     |                            |
|           |            |         |     |                            |
| (58630-2) |            |         |     |                            |
+-----------+------------+---------+-----+----------------------------+
| I-Ching   | Indoor     | M       | 9   | 1 ounce per 3 ft^3^ -      |
| Na        | storage    | othball | 9.9 |                            |
| phthalene | areas      |         |     | 0.25 lb ai / Average       |
| Moth      | (          |         |     | Garment Bag (12 ft^3^)     |
| Balls     | containers |         |     |                            |
|           | and        |         |     | 0.33 lb ai / Large Trunk   |
| (80305-1) | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| IMS Old   | Indoor     | M       | 99  | 1.5 ounces per 3 ft^3^ -   |
| Fashioned | storage    | othball | .95 |                            |
| Moth      | areas      |         |     | 0.37 lb ai / Average       |
| Balls     | (          |         |     | Garment Bag (12 ft^3^)     |
|           | containers |         |     |                            |
| (81433-6) | and        |         |     | 0.36 lb ai / Large Trunk   |
|           | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
|           |            |         |     | 1.1 lb ai / Small Closet   |
|           |            |         |     | (50 ft^3^)                 |
+-----------+------------+---------+-----+----------------------------+
| Moth      | Indoor     | M       | 9   | 1 ounce per 3 ft^3^ -      |
| Avoid     | storage    | othball | 9.7 |                            |
| Brand     | areas      |         |     | 0.25 lb ai / Average       |
| Tr        | (          |         |     | Garment Bag (12 ft^3^)     |
| aditional | containers |         |     |                            |
| Moth      | and        |         |     | 0.33 lb ai / Large Trunk   |
| Balls     | storage    |         |     | (15 ft^3^)                 |
|           | closets)   |         |     |                            |
| (83424-2) |            |         |     | 1 lb ai / Small Closet (50 |
|           |            |         |     | ft^3^)                     |
+-----------+------------+---------+-----+----------------------------+
| **Outdoor |            |         |     |                            |
| Use**     |            |         |     |                            |
+-----------+------------+---------+-----+----------------------------+
| F&B       | Soil       | Dust    | 15  | 0.45 lb ai/ treated area   |
| Rabbit    | treatment  |         |     | (3 lb container)           |
| and Dog   | on         |         |     |                            |
| Chaser    | ornamental |         |     | (assuming entire contents  |
|           | plants,    |         |     | used to treat area)        |
| (4-465)   | paved      |         |     |                            |
|           | areas      |         |     |                            |
+-----------+------------+---------+-----+----------------------------+
| ENOZ®     | Around the | Flake   | 99  | 2.5 lb ai/ treated area    |
| Skat!     | perimeter  |         | .45 | (2.5 lb container)         |
|           | of         |         |     |                            |
| (         | ornamental |         |     | (assuming entire contents  |
| 1475-146) | plants     |         |     | used to treat area)        |
+-----------+------------+---------+-----+----------------------------+
| Dr. T's   | Around the | Granule | 7   | 0.28 lb ai/treated area (4 |
| Sn        | perimeter  |         |     | lb container)              |
| ake-A-Way | of         |         |     |                            |
| Snake     | domestic   |         |     | 2 lb ai/ treated area (28  |
| Repellant | dwellings  |         |     | lb container)              |
|           | (          |         |     |                            |
| (58630-1) | outdoors), |         |     | (assuming entire contents  |
|           | wood       |         |     | used to treat area)        |
|           | piles,     |         |     |                            |
|           | utility    |         |     |                            |
|           | houses,    |         |     |                            |
|           | barns,     |         |     |                            |
|           | trash      |         |     |                            |
|           | cans,      |         |     |                            |
|           | flower     |         |     |                            |
|           | beds, and  |         |     |                            |
|           | gardens    |         |     |                            |
+-----------+------------+---------+-----+----------------------------+
| Dr. T's   | Around the | Flake   | 99  | 4 lb ai/ treated area (4   |
| Rabbit,   | perimeter  |         | .95 | lb container)              |
| Squirrel, | of         |         |     |                            |
| Bat &     | ornamental |         |     | 24 lb ai/ treated area (24 |
| Bird      | plants     |         |     | lb container)              |
| Repellant |            |         |     |                            |
|           |            |         |     | (assuming entire contents  |
| (58630-2) |            |         |     | 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.

2.  []{#__RefHeading___Toc192045121 .anchor}**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, 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 direct comparison of human exposure study results and points of
departure (LOAEL/NOAEL) from animal studies were estimated for adult and
toddler exposure from accessing (i.e., dresser drawers and closets) and
inhabiting indoor areas previously treated with naphthalene and 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.

[]{#__RefHeading___Toc192045122 .anchor}**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. Number range
CHAPTERJob 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.

[]{#__RefHeading___Toc192045123 .anchor}**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:

1.  Hand application of naphthalene formulations for indoor moth
    treatments

2.  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 ft^3^ 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 /m^3^,
0.87 mg /m^3^ and 0.90 mg /m^3^, 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/m^3^ in the dresser drawer and from 1.49 to 12.29 mg/m^3^ 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/m^3^. 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/m^3^.
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/m^3^. A summary of all average 24-hour air concentrations are
summarized in Table 6.

+---------------+--------------+------------------+--------------------+
| **Table 4.    |              |                  |                    |
| Applicator    |              |                  |                    |
| Hand Exposure |              |                  |                    |
| ( mg/cm^2^)   |              |                  |                    |
| Based on      |              |                  |                    |
| Cotton Glove  |              |                  |                    |
| Dosimeters**  |              |                  |                    |
+---------------+--------------+------------------+--------------------+
| Trial         | Naphthalene  | Contact Surface  | Naphthalene Hand   |
|               | Residue -    | Area of Both     | Exposure           |
|               | Both Hands   | Gloves           |                    |
|               | (mg/lb ai)   |                  | (mg/cm^2^)         |
|               |              | (cm^2^)          |                    |
+---------------+--------------+------------------+--------------------+
| 92-           | 0.00807      | 407              | 1.98E-05           |
| 298-01-21H-02 |              |                  |                    |
+---------------+--------------+------------------+--------------------+
| 92-           | 0.104        | 407              | 2.56E-04           |
| 298-01-21H-03 |              |                  |                    |
+---------------+--------------+------------------+--------------------+
| 92-           | 0.0465       | 407              | 1.14E-04           |
| 298-01-21H-04 |              |                  |                    |
+---------------+--------------+------------------+--------------------+
| Mean          | **0.053**    | 407              | 1.30E-04           |
+---------------+--------------+------------------+--------------------+

+--------------+--------------+------------------+--------------------+
| **Table 5.   |              |                  |                    |
| Post         |              |                  |                    |
| -Application |              |                  |                    |
| Inhalation   |              |                  |                    |
| Exposure     |              |                  |                    |
| (Acute) --   |              |                  |                    |
| (mg/m^3^)**  |              |                  |                    |
+--------------+--------------+------------------+--------------------+
| Site \#      | Average      | Average Day 5    | Average Day 6 Air  |
|              |              | Air              | Concentration      |
|              | Day 4 Air    | Concentration    | (mg/m^3^)          |
|              | C            | (mg/m^3^)        |                    |
|              | oncentration |                  |                    |
|              | (mg/m^3^)    |                  |                    |
+--------------+--------------+------------------+--------------------+
| 92-2         | 0.49         | 0.48             | 0.63               |
| 98-01-21H-02 |              |                  |                    |
+--------------+--------------+------------------+--------------------+
| 92-2         | 0.85         | 1.1              | 1.3                |
| 98-01-21H-03 |              |                  |                    |
+--------------+--------------+------------------+--------------------+
| 92-2         | 0.98         | 1.0              | 0.74               |
| 98-01-21H-04 |              |                  |                    |
+--------------+--------------+------------------+--------------------+
| Overall      | 0.77         | 0.87             | 0.90               |
| Average      |              |                  |                    |
+--------------+--------------+------------------+--------------------+

  ----------------------------------- -----------------------------------
  Mean                                **0.85 mg/m^3^**

  ----------------------------------- -----------------------------------

<table style="width:100%;">
<colgroup>
<col style="width: 7%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 10%" />
<col style="width: 9%" />
</colgroup>
<thead>
<tr class="header">
<th colspan="10"><strong>Table 6. Postapplication Air Concentration of
Naphthalene (Short-Term) - (mg/m<sup>3</sup>)</strong></th>
</tr>
<tr class="odd">
<th>Hours</th>
<th><p>Average</p>
<p>Day 4 Naphthalene Air Concentration Adjacent to Dresser Drawer
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 5 Naphthalene Air Concentration Adjacent to Dresser Drawer
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 6 Naphthalene Air Concentration Adjacent to Dresser Drawer
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 4 Naphthalene Air Concentration Adjacent to Closet
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 5</p>
<p>Naphthalene Air Concentration Adjacent to Closet
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 6</p>
<p>Naphthalene Air Concentration Adjacent to Closet
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 4 Naphthalene Air Concentration Adjacent to Bed
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 5 Naphthalene Air Concentration Adjacent to Bed
(mg/m<sup>3</sup>)</p></th>
<th><p>Average</p>
<p>Day 6</p>
<p>Naphthalene Air Concentration Adjacent to Bed
(mg/m<sup>3</sup>)</p></th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td colspan="10">92-298-01-21H-02</td>
</tr>
<tr class="even">
<td>0 – 8</td>
<td>0.48</td>
<td>0.41</td>
<td>0.36</td>
<td>0.50</td>
<td>0.44</td>
<td>0.64</td>
<td>0.52</td>
<td>0.37</td>
<td>0.64</td>
</tr>
<tr class="odd">
<td>8 – 16</td>
<td>0.45</td>
<td>0.50</td>
<td>0.69</td>
<td>0.53</td>
<td>0.53</td>
<td>0.72</td>
<td>0.39</td>
<td>0.46</td>
<td>0.66</td>
</tr>
<tr class="even">
<td>16 - 24</td>
<td>0.24</td>
<td>0.52</td>
<td>0.92</td>
<td>0.27</td>
<td>0.61</td>
<td>0.81</td>
<td>0.25</td>
<td>0.58</td>
<td>0.83</td>
</tr>
<tr class="odd">
<td>Avg.</td>
<td>0.39</td>
<td>0.48</td>
<td>0.66</td>
<td>0.43</td>
<td>0.53</td>
<td>0.72</td>
<td>0.39</td>
<td>0.47</td>
<td>0.71</td>
</tr>
<tr class="even">
<td colspan="10">92-298-01-21H-03</td>
</tr>
<tr class="odd">
<td>0 – 8</td>
<td>0.76</td>
<td>0.93</td>
<td>1.10</td>
<td>0.73</td>
<td>0.86</td>
<td>0.98</td>
<td>0.68</td>
<td>0.87</td>
<td>1.03</td>
</tr>
<tr class="even">
<td>8 – 16</td>
<td>0.94</td>
<td>1.05</td>
<td>1.02</td>
<td>0.95</td>
<td>0.95</td>
<td>0.91</td>
<td>0.99</td>
<td>1.05</td>
<td>0.98</td>
</tr>
<tr class="odd">
<td>16 - 24</td>
<td>0.73</td>
<td>0.66</td>
<td>0.55</td>
<td>0.71</td>
<td>0.60</td>
<td>0.54</td>
<td>0.58</td>
<td>0.66</td>
<td>0.57</td>
</tr>
<tr class="even">
<td>Avg.</td>
<td>0.81</td>
<td>0.88</td>
<td>0.89</td>
<td>0.80</td>
<td>0.80</td>
<td>0.81</td>
<td>0.75</td>
<td>0.86</td>
<td>0.86</td>
</tr>
<tr class="odd">
<td colspan="10">92-298-01-21H-04</td>
</tr>
<tr class="even">
<td>0 – 8</td>
<td>0.65</td>
<td>0.64</td>
<td>0.57</td>
<td>0.73</td>
<td>0.91</td>
<td>0.63</td>
<td>0.65</td>
<td>0.60</td>
<td>0.56</td>
</tr>
<tr class="odd">
<td>8 – 16</td>
<td>0.71</td>
<td>0.63</td>
<td>0.47</td>
<td>0.92</td>
<td>0.69</td>
<td>0.56</td>
<td>0.72</td>
<td>0.54</td>
<td>0.43</td>
</tr>
<tr class="even">
<td>16 - 24</td>
<td>0.55</td>
<td>0.49</td>
<td>0.50</td>
<td>0.77</td>
<td>0.67</td>
<td>0.62</td>
<td>0.52</td>
<td>0.47</td>
<td>0.41</td>
</tr>
<tr class="odd">
<td>Avg.</td>
<td>0.64</td>
<td>0.59</td>
<td>0.51</td>
<td>0.81</td>
<td>0.76</td>
<td>0.60</td>
<td>0.63</td>
<td>0.54</td>
<td>0.47</td>
</tr>
<tr class="even">
<td>Day/Site Avg.</td>
<td>0.61</td>
<td>0.65</td>
<td>0.69</td>
<td>0.68</td>
<td>0.70</td>
<td>0.71</td>
<td>0.59</td>
<td>0.62</td>
<td>0.68</td>
</tr>
</tbody>
</table>

  ----------------------- -----------------------------------------------
  Geometric Mean          **0.66 mg/m^3^**

  ----------------------- -----------------------------------------------

**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 ft^3^) and 3 dresser drawers (90 ft^3^) are treated at 0.0625
    lb ai/ 3 ft^3^;

-   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       | **Total          | **Daily Exposure  | **MOE**    |
| Scenario**       | Applied**        | (mg/ lb ai)**     |            |
|                  |                  |                   | **(LOC =   |
|                  | **(lb ai)**      |                   | 100)**     |
+------------------+------------------+-------------------+------------+
| 1 - Apply Moth   | 14.4             | 0.053             | 28000      |
| Treatment by     |                  |                   |            |
| Hand             |                  |                   |            |
+------------------+------------------+-------------------+------------+
| 2 -- Apply       | 24               | 0.053             | 17000      |
| Animal Repellant |                  |                   |            |
| Treatment by     |                  |                   |            |
| Hand             |                  |                   |            |
+------------------+------------------+-------------------+------------+

2.  []{#__RefHeading___Toc192045124 .anchor}**Residential Handler Cancer
    Exposure and Risk**

Residential handler cancer exposure and risk estimates were not assessed
due to the uncertainty of whether naphthalene poses a human cancer
concern at ambient or environmental levels of exposure because of
potential species differences in rates of metabolism leading to its
toxicity.

1.  []{#__RefHeading___Toc192045125 .anchor}**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.

[]{#__RefHeading___Toc192045126 .anchor}**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).

Since the data available to date indicate that rodents are more
susceptible to the respiratory toxicity of naphthalene, the use of
rodents as a model without the appropriate species scaling accounting
for species differences in dosimetry would likely result in an
inaccurate estimation of human risk. Therefore, 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.

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.

[]{#__RefHeading___Toc192045127 .anchor}**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

1.  Acute inhalation from accessing treated areas

Adult/Toddler

2.  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/m^3^
for acute and short-term durations of exposure, respectively. These
results fall well within the range (0.23 -- 7.5 mg/m^3^) 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/m^3^ in a cupboard containing mothballs (Lau et al., 1995);

-   7.5 mg/m^3^ in a closet, 1.2 in a bedroom, 0.90 mg/m^3^ in a living
    room, 0.35 mg/m^3^ in a garage, and 0.23 mg/m^3^ outdoors of a home
    which had closets treated liberally with mothballs (Gammage and
    Matthews, 1987); and

-   0.68 mg/m^3^ 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/m^3^) in                                             
  Indoor Air of                                            
  the 24                                                   
  Low-Income                                               
  Homes**                                                  

  **Mean**         **Standard           **Minimum**        **Maximum**
                   Deviation**                             

  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 of points of departure (LOAEL/NOAEL) from
animal studies resulting in toxic outcomes in the rodents 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/m^3^ of naphthalene, respectively. These values were
compared directly to the animal LOAEL (10 ppm or 52 mg/m^3^) and NOAEL
(3 ppm or 16 mg/m^3^) selected for acute and short-term exposure
durations.\
 \
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/m^3^. This exposure value was
directly compared to the animal LOAEL for olfactory epithelium lesions
selected for intermediate- (2 ppm or 10 mg/m^3^ identified in a
nose-only study) and long-term (10 ppm or 52 mg/m^3^ identified in an
exposure chamber study) durations, as well as, the NOAEL selected for
the intermediate-term duration (1 ppm or 5.2 mg/m^3^). 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.

[]{#__RefHeading___Toc192045128 .anchor}**2.2.3** **Residential
Postapplication Cancer Exposure and Risk**

Residential postapplication cancer exposure and risk estimates were not
assessed due to the uncertainty of whether naphthalene poses a human
cancer concern at ambient or environmental levels of exposure because of
potential species differences in rates of metabolism leading to its
toxicity.

[]{#__RefHeading___Toc192045129 .anchor}**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.

[]{#__RefHeading___Toc192045130 .anchor}**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

1.  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).

[]{#__RefHeading___Toc192045131 .anchor}**References**

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

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

3.  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.

4.  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.

[]{#__RefHeading___Toc192045132 .anchor}**APPENDIX A**

**STANDARD FORMULAS USED FOR**

**CALCULATING RESIDENTIAL**

**EXPOSURES TO NAPHTHALENE**

[]{#__RefHeading___Toc192045133 .anchor}**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.

[]{#__RefHeading___Toc192045134 .anchor}**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 ft^3^, and 3 closets and 3
dressers drawers total 690 ft^3^, 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]{.underline}**:**

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

(mg/day) (mg/ lb ai) (lb ai/ ft^3^) (ft^3^/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/ ft^3^)

Area treated = normalized application area (690 ft^3^/day)

[Absorbed Daily Dose is calculated]{.underline}**:**

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:]{.underline}

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)

The level of concern for residential handlers is an MOE = 100. Scenarios
with MOEs ≥ 100 are not of concern to HED for the residential
population.

[]{#__RefHeading___Toc192045135 .anchor}**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:]{.underline}

PDR = IgR \* F \* CF1

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

PDR = 2349 mg/day

[The PDR~norm~ value was then calculated using the following
equation:]{.underline}

PDR~norm~ = PDR / BW

PDR~norm~ = (2349 mg/day) / (15 kg)

PDR~norm~ = 156.6 mg/kg/day

[The MOEs for episodic ingestion are calculated for using the MOE
formula:]{.underline}

MOE (unitless) = NOAEL / (Dose)

Where:

NOAEL = 50 mg/kg/day (short-term)

Dose = 156.6 mg/kg/day