Page 2 of 2 revised risk estimates which are provided in Table 1 below. These corrections do not alter the

risk conclusions as described in D371250.

The Agency is also anticipating additional data from the registrants which will provide chemical and formulation specific information on pet fur re sidue transferability. These data are a more direct and appropriate measurement of the resi dues coming off pet fur than provided in the interim data. It is possible that these data will also reduce risk estim ates given the trends observed in the interim data, but it is not appropriate to predict a qua ntitative effect at this time.

The Agency has accounted for the error correc tion based on the amount of active ingredient present in each type of collar. Though the Agen cy believes that risks may be of less concern than indicated by the calculated margins of expos ure below, revised risk estimates will not be quantitatively calculated until all anticipated data have been received and reviewed.

Table 1. Revised Risk Estimates Based on Error Correction.

Summary of Post-application Child Hand-to-Mou th Exposure/Risk from Contacting Pets Wearing Propoxur Collars with 20% Available for Transfer Over 15 Days

Scenario Net

Amount 1 Days SA PET 2
(cm 2 ) Dose (mg/kg/day) NOAEL (mg/kg/day) LOC MOE 3

Wellmark International Dog Collar 34 g (1.2 oz) 5986 0.0051 55 Cat Collar 10.5 g (0.37oz) 15 2737 0.0034 0.28 1000 82

Sergeant’s Pet Care Products, Inc

Dog Collar 30 g (1.1 oz) 5986 0.0043 70 Cat Collar 14 g (0.5 oz) 15 2737 0.0041 0.28 1000 68 1. The net amount reported is the maximum amount based on prod uct packaging submitted by Wellmark International (EPA Reg No. 2724-493 and 2724-491) and Sergeant’s Pet Care Products, Inc (EPA Reg No. 2517-61 and 2517-78). Maximum amount of propoxur indicated in D371250 fo r Wellmark International and Sergeant’s Pet Care Products, Inc was 1.5 oz and 1.2 oz, respectively. 2. Surface area of the treated pet is calculated using the bod y weight to surface conversion algorithm: SA = 12.3*(lbs of pet*454)^(0.65). A medium sized dog and cat were assumed to be 30 and 9 lbs, respectively.

.3. Risk estimates in D371250 indicated MOEs of 44 and 20 for We llmark International dog and cat collars, respectively, and 62 and 28 for Sergeant’s Pet Care Products, Inc dog and cat collars, respectively.Page 2 of 11 Executive Summary

Propoxur [o-isopropoxyphenyl methylcarbamate] is a carbamate insecticide registered under 37 currently active labels for use by pest control operators to control an ts, roaches, hornets, and other pests in and around commerci al, industrial, and institutional buildings as we ll as in food handling establishments and outside residences . Propoxur may also be used by homeowners in granular, paste, and impregnated fo rmulations (i.e., pet collars and ba it strips) of the insecticide. It was first registered in 1963. Exposures to pro poxur can be expected to occur via the dietary as well as through the occupa tional and residential ha ndler and post-applicati on routes of exposure.

Propoxur is in the toxicity category II by oral routes, category III by dermal, inhalation, and eye

irritation. The most sensitive indication of toxic ity is inhibition of red blood cell (RBC) ChE. A

BMDL 10 analysis was also conducted based on ChEI in the brain. While propoxur is classified as a Group B2: Probable human carcinogen by the U. S. EPA with a linear low-dose approach for quantification of risk usi ng the oral slope factor (Q 1 *) of 3.7 x 10 -3 (mg/kg/day), this linear lowdose approach was based on concentrations of e xposure that were orders of magnitudes greater than what is currently allowable for propoxur. Therefore, a cancer occupational and residential

assessment for adults and children was not conducted.

Risk estimates for handling of propoxur pet collar products in the residential setting as well as occupational settings were not assessed as part of this risk assessment because no endpoints have been identified for dermal exposure which is the only viable route of exposure for the handling of the pet collar formulation of propoxur. The vapor pressure for propoxur is 6.5 x 10 -6 mmHg and, given the formulation of propoxur in pet collars , inhalation is not consid ered to be a viable route of exposure. Therefore, no inhalation exposure or risk estimate is reported as part of this assessment. Incidental oral ingestion (hand-to-m outh) exposure is not anti cipated for residential handler or occupational exposure with the pet colla r because applicators are assumed to be adults and hand-to-mouth exposure is only assessed for children less than six years of age

.

Residential post-application risk from exposure to the propoxur pet collar was assessed using the Agency’s Standard Operating Procedures (SOP s) for Residential Exposure Assessments (1997) and appropriate default values. Re sults indicate that ch ild residential post-a pplication incidental oral ingestion (hand-to-mouth) exposure is of concern to th e Agency (i.e., an MOE < 1000). While post-application dermal exposure to the propoxur collar is anticipated for children and adults, this route of exposure ha s not been assessed due the lack of a dermal endpoint (i.e., no

adverse effects were measured at the limit dos e, 1000 mg/kg/day). The vapor pressure for propoxur is 6.5 x 10 -6 mmHg and, given the formulation of pr opoxur in pet collars, inhalation is not considered to be a viable route of expos ure. Therefore, no inha lation exposure or risk estimate is reported as part of this assessment.

Post-application exposure from o ccupational application of pet co llars is anticipated to be negligible since minimal involveme nt with the animal is anticipated to occur post-treatment. Furthermore, if contact with the animal did o ccur, it is assumed that a greater potential for exposure exists from the direct occupational application of the pet collar product.Page 3 of 11 1.0 Use Profile

Propoxur [o-isopropoxyphenyl methylcarbamate] is a carbamate insecticide registered under 37 currently active labels for use by pest control operators to control an ts, roaches, hornets, and other pests in and around commerci al, industrial, and institutional buildings as we ll as in food handling establishments and outside residences . Propoxur may also be used by homeowners in granular, paste, and impregnated fo rmulations (i.e., pet collars and ba it strips) of the insecticide. It was first registered in 1963. Exposures to pro poxur can be expected to occur via the dietary as well as through the occupa tional and residential ha ndler and post-applicati on routes of exposure.

The propoxur pet collar product was first register ed in 1975. Pet collar labels are currently registered under both Wellmark International an d Sergeant’s Pet Care Products. These pet collar products contain the active ingred ient propoxur with percent active ingredient of 9% (Sergeant’s Pet Care Products) and 10% (Wellmark International). The collar is a ready to use (RTU) product formulated for residential use to contro l fleas and ticks on both dogs and cats. The amount of active ingredient per collar range s from 0.0012 to 0.0094 lbs a.i./unit depending on the net weight of the collar, as it is marketed in different sizes base d upon pet weight ranges.

2.0 Hazard Concerns

Propoxur is an N -methyl carbamate (NMC) insecticide in which the mode of action is carbamylation of acetylcholinesterase. The N -Methyl Carbamate Cumulative Risk Assessment (NMC CRA) can be referenced for the most current toxicological data in regard to propoxur. Points of Departure (PoDs) required to assess th e residential exposure/risk including short- and

intermediate-term incidental oral (child) endpoints.

Incidental Oral : Since the 1996 completion of the HE D Chapter of the RED for Propoxur (TXR# 012005), a revised NMC CRA was conducted (September, 24, 2007). The points of departure for this assessment were taken from the revised N - Methyl Carbamate Cumulative Risk Assessment document as the latest toxicity info rmation was utilized; therefore, EPA used the same benchmark dose (BMD) modeling approach that was developed for the OP cumulative risk assessment to assess the N-methyl carbamates. Analyses were conducted to estimate BMD 10 s and BMDL 10 s for brain and RBC AChE inhibition. The BMD 10 is the estimated dose resulting

in 10% ChE inhibition. The BMDL 10 is the lower 95% confidence limit on the BMD 10

. Consistent with EPA policy, the BMDL is used as the point of departure for propoxur as with other NMCs. At the present time, the only RBC a nd whole brain ChE data via the oral route for propoxur are the EPA’s NHEERL dose - response and time course stud ies in male rats (Padilla et
al ., 2007). The appropriate acute oral time-course and recovery data for propoxur were provided by the NHEERL or ORD (Padilla et al ., 2007). Refer to Table 1 for the points of departure for

propoxur.

The 10x intraspecies and 10x interspecies factor s are applicable. In addition, the Agency does not have a comparative cholinesterase study th at evaluates the sensit ivity of young animals compared to the adult animals; therefore, the Agency retained a 10X FQPA factor for propoxur. A margin of exposure (MOE) of 1000 de fines HED’s level of concern (LOC).Page 4 of 11 Dermal : In the 90-day dermal toxicity study in rabbits (MRID 41066001), ChE inhibition was not observed at various time points following 6 h ours of exposure. No dermal or systemic toxicity was observed at 1000 mg/ kg/day (limit dose) and, therefore, a dermal endpoint was not established for propoxur. In addition, dermal ab sorption data are not available for propoxur.

Inhalation : A chronic inhalati on study (MRID 42648001; 40836402) is available that measured ChE activity within the appropriate time for peak effect after the last exposure. Inhalation is not considered to be a viable route of exposure fo r the formulated pet collar use; therefore, no inhalation exposure or risk estimate is reported as part of this assessment.

FQPA Considerations : As with other NMCs, propoxur inhibits acetylcho linesterase (AChE) by carbamylation of the serine hydr oxyl group located in the active site of the enzyme. Toxicological characteristics of propoxur like the other NMCs involves maximal ChE inhibition (typically within 15 minutes to an hour) followe d by rapid reactivation of the enzyme and then recovery (minutes to hours). As such, the critical duration of exposure for propoxur is acute ChE

inhibition of brain and RBC AChE measured at the peak time of effect. Although the Agency has an acute and subchronic neurotoxicity stud y, these studies did not appropriately measure ChE activity for propoxur. The Agency does not ha ve a comparative cholinesterase study that evaluates the sensitivity of young animals compared to the a dult animals to address the FQPA factor in risk assessment. Therefore, the Ag ency retained a 10X FQPA factor for propoxur.

Cancer : Propoxur was classified as a Group B; “Probable Hu man Carcinogenic” and was assessed for carcinogenic risk from exposure usin g a linear, low dose extrapolation approach with a Q 1 * is 3.69 x 10 -3 (mg/kg/day). Classification was based on dose- related and highly significant increased incidence of urinary bladde r papillomas and carcinomas in both sexes, and a borderline statistically significant increased incidence of uterine carcinomas in high- dose females (MRID 00142725). However, this li near low-dose approach was based on concentrations of exposure that were orders of magnitudes greater th an what is currently allowable for propoxur. In addition, based on the cu rrent knowledge of the mode of action for propoxur (i.e., rapid reactivation of recovery) and the other N -methyl carbamates, a cancer assessment is not appropriate.

A hazard summary detailing the updates based on the N -Methyl Carbamate Cumulative Risk Assessment and benchmark dose analysis are su mmarized above and are outlined in Table 1,

below.

Table 1: Summary of Toxicological Doses and Endpoints for Propoxur Human Health

Risk Assessment

Exposure/

Scenario Point of Departure Uncertainty/ FQPA Safety

Factors RfD, PAD, Level of

Concern for Risk

Assessment Study and Toxicological

Effects

Acute Dietary (all population) BMDL 10 = 0.28 mg/kg/day UF A = 10X

UF H = 10X FQPA SF= 10X

Total UF= 1000X aPAD= Acute RfD FQPA SF

aPAD= 0.00028 mg/kg/day Padilla et al ., 2007.

BMD 10 = 1.54 mg/kg/day

BMDL 10 = 0.28 mg/kg/day

based on RBC ChE inhibition

in adult male ratsPage 5 of 11 Table 1: Summary of Toxicological Doses and Endpoints for Propoxur Human Health

Risk Assessment

Exposure/

Scenario Point of Departure Uncertainty/ FQPA Safety

Factors RfD, PAD, Level of

Concern for Risk

Assessment Study and Toxicological

Effects

Incidental

oral (Short and

intermediate term) BMDL 10 = 0.28 mg/kg/day UF A = 10X

UF H = 10X FQPA SF= 10X

Total UF= 1000X Residential LOC= 1000 Padilla et al ., 2007.

BMD 10 = 1.54 mg/kg/day

BMDL 10 = 0.28 mg/kg/day

based on RBC ChE inhibition

in adult male rats

Inhalation (Short and

intermediateterm) BMDL 10 F= 0.0076 mg/L UF A = 10X

UF H = 10X FQPA SF= 10X Residential LOC= 1000 Occupational LOC= 100 Chronic inhalation study – Rats (MRID 42648001; 40836402)

BMD 10 F= 0.0095 mg/L

BMDL 10 F = 0.0076 mg/L

based on ChE in the brain

BMD 10 M= 0.016 mg/L

BMDL 10 M = 0.011 mg/L

based on ChE in the brain

Dermal A risk assessment for dermal exposure of any dura tion is not required as no adverse effects were observed at the highest dose tested (1000 mg/kg/day) (MRID 41066001).

Cancer (oral & dermal) Classification: Group B; “ Probable Human Carcinogenic ” based on dose- related and highly significant increased incidence of urinary bladde r papillomas and carcinomas in both sexes, and a borderline statistically significant increased incide nce of uterine carcinomas in high- dose females
(MRID 00142725). The Q 1 * is 3.69 x 10 -3 (mg/kg/day ).

Point of Departure (POD) = A data point or an estimated point 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). LOC = level of concern. MOE = margin of exposure. BMDL 10 = lower 95% confidence limit of the 10% benchmark response, in this case the estimated dose resulting in 10% ChE inhibition.

3.0 Occupational Handler and Post-application Exposure/ Risks

HED determined there is potential for short-te rm exposure in occupational settings during the application of the pet co llar product. No assessme nt of exposure/risk from pet collar application (handling) in occupational settings was performed in the 1997 Reregistration Eligibility Document (1997 RED) nor as part of the NMC Cumulative Risk A ssessment. Risk estimates for occupational handling of propoxur pet collar were not assessed as part of this risk assessment because no endpoints have been identified for derm al exposure which is the only viable route of exposure for the handling of the pet collar fo rmulation of propoxur. The vapor pressure for propoxur is 6.5 x 10 -6 mmHg and, given the formulation of pr opoxur in pet collars, inhalation is not considered to be a viable route of expos ure. Therefore, no inha lation exposure or risk estimate is reported as part of this assessment. Hand-to-mouth exposure is not anticipated for occupational exposure with the pet collar because applicators are assumed to be adults and handto-mouth exposure is only assessed for children less than six years of age

.Page 6 of 11 Post-application exposure from o ccupational application of pet co llars is anticipated to be negligible since minimal involvement with the an imal is anticipated to occur post-treatment. Furthermore, if contact with the animal did o ccur, it is assumed that a greater potential for exposure exists from the direct occupational application of the pet collar product.

4.0 Residential Handler and Po st-application Exposure/Risks

It has been determined that there is a potential for exposure in residential settings during the application process for homeowners who purchase and use the propoxur pet co llar. There is also potential for post-application exposure from c ontacting a companion animal previously treated with the pet collar.

Residential risks are typically calculated for short- and intermediate-term exposures because repeated exposures are likely. Since peak inhi bition of cholinesterase occurs rapidly with recovery occurring within hours, th e daily exposure to propoxur is the main duration of concern. Therefore, endpoints selected for short- and intermediate-terms r outes of exposure are the same

and i ntermediate-term (30 days to several months) exposure was not assessed for the propoxur pet

collar.

4.1 Residential Handler Exposure/Risks

The Agency uses the term “handlers” to desc ribe those individuals who are involved in the pesticide application process. The Agency beli eves that there are distinct tasks related to applications and that exposures can vary dependi ng on the specifics of each task. The amount of chemical to be used in an application, the kinds of equipment used and the target being treated can cause exposure levels to differ in a ma nner specific to each application event.

HED has determined that there is potential for sh ort-term exposure through the dermal route of exposure in residential settings dur ing the application of the pet co llar product. However, given that there is no dermal endpoint for propoxur, an exposure and risk estimate and assessment has not been performed. The vapor pressure for propoxur is 6.5 x 10 -6 mmHg and, given the formulation of propoxur in pet collars, inhalation is not considered to be a viable route of exposure. Therefore, no inhalation exposure or risk estimate is reported as part of this assessment. Hand-to-mouth exposure is also not an ticipated for the applic ation of a pet collar because applicators are assumed to be adults and hand-to-mouth exposure is only assessed for children less than six years old

.

4.2 Residential Post-application Exposure/Risks

The Agency uses the term “post-application” to de scribe exposures to individuals that occur as a result of being in an environment that has been previously treated with a pesticide. Propoxur can be used in limited areas that can be frequent ed by the general populati on including outside of

residential areas or within commercial and indust rial areas. As a resu lt, individuals can be exposed by entering these areas if they have been previously treated. The use of a propoxur pet collar can result in exposur e through contact with a previously treated animal and is, therefore, subject to post-applic ation assessment.Page 7 of 11 A quantitative assessment of residential post-ap plication exposure of a propoxur pet collar was conducted in the 1997 RED using surrogate data based on propoxur pest strips and dog aerosol spray treatment data. An inhalation exposure of 6.3 x 10 -6 mg/kg/day was calculated. In addition, residential post-application risk was assessed in the 2007 NMC CRA for propoxur pet collars. Based on inputs, assumptions, and algorithms th at were specific to the cumulative risk assessment, the propoxur pet collar dermal and incide ntal oral ingestion risk estimates were not

of concern at that time. The current assessmen t is based on the anticipated exposure from the single chemical and risk and chemical specific toxicological informati on as described above.

HED has determined that exposure to propoxur is likely following residentia l pet collars use. Adults and children are likely to contact a previously treated pet, however, since no dermal endpoint was selected, only child incidental oral ingestion (hand-to-mouth) exposure was

assessed. The incidental oral i ngestion exposure scenario usi ng default inputs and a 15 day average result in MOEs ≤ 62, this scenario exceeds the Agency ’s level of concern (MOE <1000).

4.2.1 Residential Post-application No ncancer Exposure/Risk Estimates

Adults and children in residential settings are lik ely to contact a pet prev iously treated with a propoxur pet collar and, therefore, risk estimates were calculated as appropriate for each. Adult exposures are limited to dermal post-applicati on exposure for which no toxicological endpoint exists; therefore, exposure/risk was not estima ted. Children can be exposed to the propoxur collar through dermal and incidental oral ingestion routes of exposure. Again, due to the lack of a dermal toxicological endpoint th is route of exposure was not a ssessed; however, the incidental oral ingestion route of exposur e was assessed for children.

The Agency combines or aggregates risks result ing from exposures to individual chemicals when it is likely they can occur simultaneously based on the use pattern and th e behavior associated with the exposed population. Children can be expo sed to a previously treated dog through either dermal or incidental oral ingest ion routes of exposure. These routes of exposure are typically aggregated; however, in the case of propoxur, de rmal risk estimates were not calculated.

Data and Assumptions

A series of assumptions and factors served as the basis for completing the residential postapplication risk assessment of a dult and child exposure to propoxur pet collars. The assumptions

and factors used in this risk assessment are cons istent with current Agency policy for completing residential exposure assessments (i.e., Draft HED SOPs for Residential Exposure Assessment (1997) and 1999 Draft Policy 13, Post-application Exposure A ssessment for Children from

Treated Pets ).

The assumptions and factors used in the risk calculations are as follows:

• The Agency always considers the maximum app lication rates allowed by labels in its risk

assessments to consider what is le gally possible based on the label;Page 8 of 11 • Pet collar products are intended to emit pestic ide residues over ex tended periods of time to ensure a level of protection for the treate d pet for that active product lifetime (i.e., 4 to 7 months is specified on current propoxur pet collar labels). The mechanisms involved in such emissions are not thoroughl y understood but it is clear th at pet collar products must provide some level of efficacy over time, i ndicating that actual time-release emissions occur from the propoxur collars. Because l ittle is known about the mechanisms of emission, it is possible that once a pet collar is placed on a pet they could be relatively constant over time or it is also plausible that higher concentrations may be emitted in the first days or weeks after initi al placement on a pet. In or der to address these types of

uncertainties and still account for the time -released nature of pet collars, a steady emission profile over the course of a 15 day pe riod was used to develop this assessment. [Note: The results of this assessment are not sensitive to other plausible averaging times in lieu of data. For example, if other values such as 30 or 60 days are considered, which still likely result in conservative estimates of exposure, they do not impact the overall results of the assessment.]

• In the absence of chemical-specific data, it may be assumed that on the day of application 20 percent (0.20) of the maximum applicati on rate is availabl e on the pet’s body and

transferred to the adult/child as a transf erable residue. This value is based on the professional judgment and experience of the O PP/HED staff from the review of data and is believed to be an upper-percent ile assumption (US EPA, 1999 SAP).

• A 3 year old child is expected to weigh 15 kilograms (representing an average weight from years one to six).

• The approach used to address the hand-to -mouth exposure pathway has been modified since 1999 Draft Policy 13, Post-application Exposure Assessment for Children from

Treated Pets . In the draft policy, contact with do gs is based on 40 events per day (20 mouthing events/day for 2 hours). For each event, the palmar surface of the hands (i.e.,

20cm 2 /event) is placed in the mouth of the child contributing to incidental oral ingestion exposure. In the revised approach, the fr equency term has been modified to an equilibrium approach analogous to the dermal exposure component (i.e., the frequency = 1 event/day). The approach was revised since the data from which the transferable

residue concentrations were determined rely on a continuous contact (grooming) technique that would lead to concentrations on the hands which are anticipated to be significantly higher than woul d result from petting/hugging.

• Hand surface area per event is 20 cm 2 , which represents the palmar surfaces of three fingers;

• Saliva extraction efficiency is 50 percent m eaning that every time the hand goes in the mouth approximately 1⁄2 of the residues on the hand are removed;

• HED’s default for the surface area of an adult hug is 5625 cm 2 , a child hug is 1875 cm 2
(US EPA, 1999 SAP).Page 9 of 11 • HED’s default for the surface area of a treated pet is 5986 cm 2 (30 lb dog) and 2737 cm 2
(9 lb cat) (calculated by an algorithm provided in US EPA, Wildlife Exposure Factors Handbook, 1993)

Post-application Exposure Assessment Algorithms

The algorithms used for the assessm ent of residential post-applica tion incidental oral ingestion (hand-to-mouth) pet exposure scenarios are as follows:

Child exposure from hand-to-mouth activity to treated companion animal :

The following demonstrates the method used to calculate hand-to-mout h exposures that are attributable to a child touching a treated compan ion pet and then placing their hands in their

mouth.

D (mg/kg/day) = TR * SAL * SA hands * Freq BW (kg)
Where:

D = daily nondietary ingestion dose from treated pets (mg/kg/day) TR = amount of residue anticipated to transfer from treated animal to the exposed individual (mg/cm 2 )

SA hands = surface area of a child’s hands (20 cm 2 ) SAL = saliva extraction factor (50%) Freq = frequency of hand-to-mouth events (1 event/day) BW = child body weight (15 kg)

TR (mg/cm 2 ) = AR * F AR SA pet

Where:

AR = application rate of the pe t collar formulation (mg a.i./event)

F AR = fraction of the maximum application rate is available on the pet’s body

and transferred to the adult/ch ild as a dislodgeable residue (unitless)

SA PET = default surface area of a treated pet (5986 cm 2 dog and 2737 cm 2 cat)

MOE = NOAEL

D

Where:

NOAEL = No Observed Adverse Effect Level (mg/kg/day) D = daily dose from hand-to-mouth pet contact (mg/kg/day)Page 10 of 11 Risk Summary

Child incidental oral ingesti on (hand-to-mouth) exposure from contacting a treated pet is of concern to the Agency (i.e., an MOE < 1000). An estimate of dermal exposure/risk was not

assessed.

Table 2 presents child hand-to-mouth exposure an d risk estimates for 20% transferability of residues over 15 day time period. This adju sted scenario resu lts in risks that are of concern to the Agency (MOEs < 1000)

.

Table 2. Summary of Post-application Child Hand-to-Mouth Exposure/Risk from Contacting Pets Wearing Propoxur Collars with 20% Available for Transfer Over 15 Days

Scenario Net

Amount 1
(oz) Days SA PET 2
(cm 2 ) Dose (mg/kg/day) NOAEL (mg/kg/day) LOC MOE

Wellmark International 3
Dog Collar 5986 0.0063 44

Cat Collar 1.5 15 2737 0.0138 0.28 1000 20
Sergeant’s Pet Care Products, Inc 4

Dog Collar 5986 0.0045 62

Cat Collar 1.2 15 2737 0.0099 0.28 1000 28

1. The net amount reported is the ma ximum amount report for the labels. 2. Surface area of the treated pet is calculated using the bod y weight to surface conversion algorithm: SA = 12.3*(lbs of pet*454)^(0.65). A medium sized dog and cat were assumed to be 30 and 9 lbs, respectively. 3. Net weight information for Wellmark International pet collar products was provided by professional communication with the OPP Registration Division (RD). 4. Net weight information for Sergeant’s Pet Care Products, In c pet collar products was provide d by professional communication with the OPP Pesticide Re-evaluation Division (PRD).

4.3 Residential Post-application Cancer Exposure/Risk Estimates

Propoxur was classified as a Gr oup B2; “ Probable Human Carci nogenic ” and was assessed for carcinogenic risk from exposure using a linear, low dose extrapolation approach with a Q 1 * is

3.69 x 10 -3 (mg/kg/day). However, this linear low-dose approach was based on concentrations of exposure that were orders of magnitudes greate r than what is currently allowable for propoxur. In addition, based on the current knowledge of the mode of action for propoxur (i.e., rapid reactivation of recovery), like other N -methyl carbamates, a cancer exposure and risk assessment is not appropriate.

5.0 Public Health and Pesticide Epidemiology Data

An updated review of propoxur incident reports was recently prepared by HED (M. Hawkins, 2009). The Office of Pesticide Programs Incident Data System (IDS) was consulted for reports of propoxur poisoning incidents o ccurring in the United States fr om 2002 to the present. The IDS includes reports of incidents from regist rant reporting, other government agencies, and

individual consumers. Of the 48 incidents reported, 8 reported incidents are reported after the use of Zodiac dog and cat pet collars. Symptoms include diarrhea, nausea, rashes, swelling, pruritus, abdominal pain, and breathing issues. Eval uation of the incident da ta is equivocal. ItPage 11 of 11 was not possible to relate them to exposure, and there is no clear evidence of a trend or exposure pattern. Therefore, at this time, the Agency can not discern any suggestion of a trend or pattern regarding the health effect s due to the alleged exposur e to the pesticide propoxur.