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 residue transferability. These data are a more 

direct and appropriate measurement of the residues coming off pet fur than provided in the 

interim data. It is possible that these data will also reduce risk estimates given the trends 

observed in the interim data, but it is not appropriate to predict a quantitative effect at this time. 

The Agency has accounted for the error correction based on the amount of active ingredient 

present in each type of collar. Though the Agency believes that risks may be of less concern 

than indicated by the calculated margins of exposure 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-Mouth Exposure/Risk from Contacting Pets 

Wearing Propoxur Collars with 20% Available for Transfer Over 15 Days 

Scenario Net 

Amount1 

Days SAPET

2

(cm2) 

Dose 

(mg/kg/day) 

NOAEL 

(mg/kg/day) 

LOC MOE3

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 product 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 for 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 body 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 Wellmark 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 ants, roaches, hornets, and 

other pests in and around commercial, industrial, and institutional buildings as well as in food 

handling establishments and outside residences. Propoxur may also be used by homeowners in 

granular, paste, and impregnated formulations (i.e., pet collars and bait strips) of the insecticide. 

It was first registered in 1963. Exposures to propoxur can be expected to occur via the dietary as 

well as through the occupational and residential handler and post-application 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 toxicity is inhibition of red blood cell (RBC) ChE. A 

BMDL10 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 using the oral slope factor (Q1*) of 3.7 x 10-3 (mg/kg/day), this linear lowdose approach was based on concentrations of exposure 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 considered 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-mouth) exposure is not anticipated for residential 

handler or occupational exposure with the pet collar 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 (SOPs) for Residential Exposure Assessments (1997) 

and appropriate default values. Results indicate that child residential post-application incidental 

oral ingestion (hand-to-mouth) exposure is of concern to the 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 has not been assessed due the lack of a dermal endpoint (i.e., no 

adverse effects were measured at the limit dose, 1000 mg/kg/day). 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. 

Post-application exposure from occupational application of pet collars is anticipated to be 

negligible since minimal involvement with the animal is anticipated to occur post-treatment. 

Furthermore, if contact with the animal did occur, 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 ants, roaches, hornets, and 

other pests in and around commercial, industrial, and institutional buildings as well as in food 

handling establishments and outside residences. Propoxur may also be used by homeowners in 

granular, paste, and impregnated formulations (i.e., pet collars and bait strips) of the insecticide. 

It was first registered in 1963. Exposures to propoxur can be expected to occur via the dietary as 

well as through the occupational and residential handler and post-application routes of exposure. 

The propoxur pet collar product was first registered in 1975. Pet collar labels are currently 

registered under both Wellmark International and Sergeant’s Pet Care Products. These pet collar 

products contain the active ingredient 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 control fleas and ticks on both dogs and cats. The 

amount of active ingredient per collar ranges 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 based 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 the residential exposure/risk including short- and 

intermediate-term incidental oral (child) endpoints. 

Incidental Oral: Since the 1996 completion of the HED 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 information 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 BMD10s 

and BMDL10s for brain and RBC AChE inhibition. The BMD10 is the estimated dose resulting 

in 10% ChE inhibition. The BMDL10 is the lower 95% confidence limit on the BMD10. 

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 and whole brain ChE data via the oral route for 

propoxur are the EPA’s NHEERL dose- response and time course studies 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 factors are applicable. In addition, the Agency does 

not have a comparative cholinesterase study that evaluates the sensitivity 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 defines 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 hours 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 absorption data are not available for propoxur. 

Inhalation: A chronic inhalation 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 for 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 acetylcholinesterase (AChE) by 

carbamylation of the serine hydroxyl 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) followed 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 study, these studies did not appropriately measure 

ChE activity for propoxur. The Agency does not have a comparative cholinesterase study that 

evaluates the sensitivity of young animals compared to the adult animals to address the FQPA 

factor in risk assessment. Therefore, the Agency retained a 10X FQPA factor for propoxur. 

Cancer: Propoxur was classified as a Group B; “Probable Human Carcinogenic” and was 

assessed for carcinogenic risk from exposure using a linear, low dose extrapolation approach 

with a Q1* is 3.69 x 10-3 (mg/kg/day). Classification was based on dose- related and highly 

significant increased incidence of urinary bladder papillomas and carcinomas in both sexes, and 

a borderline statistically significant increased incidence of uterine carcinomas in high- dose 

females (MRID 00142725). However, this linear low-dose approach was based on 

concentrations of exposure that were orders of magnitudes greater 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) 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 summarized 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) 

BMDL10= 

0.28 

mg/kg/day 

UFA= 10X 

UFH= 10X 

FQPA SF= 10X 

 

Total UF= 1000X 

aPAD= Acute RfD

 FQPA SF 

aPAD= 0.00028 

mg/kg/day 

Padilla et al., 2007. 

BMD10 = 1.54 mg/kg/day 

BMDL10 = 0.28 mg/kg/day 

based on RBC ChE inhibition 

in adult male rats 
Page 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) 

BMDL10= 

0.28 

mg/kg/day 

UFA= 10X 

UFH= 10X 

FQPA SF= 10X 

 

Total UF= 1000X 

Residential LOC= 1000 

Padilla et al., 2007. 

BMD10 = 1.54 mg/kg/day 

BMDL10 = 0.28 mg/kg/day 

based on RBC ChE inhibition 

in adult male rats 

Inhalation 

(Short and 

intermediateterm)

BMDL10 F= 

0.0076 mg/L 

UFA = 10X 

UFH = 10X 

FQPA SF= 10X 

Residential LOC= 1000 

Occupational LOC= 100 

Chronic inhalation study – 

Rats (MRID 42648001; 

40836402) 

BMD10 F= 0.0095 mg/L 

BMDL10 F= 0.0076 mg/L 

based on ChE in the brain 

BMD10 M= 0.016 mg/L 

BMDL10 M= 0.011 mg/L 

based on ChE in the brain 

Dermal A risk assessment for dermal exposure of any duration 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 bladder papillomas and carcinomas in both sexes, and a 

borderline statistically significant increased incidence of uterine carcinomas in high- dose females 

(MRID 00142725). The Q1* 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. UFA = extrapolation from animal to human (interspecies). UFH = potential variation in 

sensitivity among members of the human population (intraspecies). LOC = level of concern. MOE = margin of 

exposure. BMDL10 = 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-term exposure in occupational settings during the 

application of the pet collar product. No assessment 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 Assessment. 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 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 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 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 occupational application of pet collars is anticipated to be 

negligible since minimal involvement with the animal is anticipated to occur post-treatment. 

Furthermore, if contact with the animal did occur, 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 Post-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 collar. There is also 

potential for post-application exposure from contacting 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 inhibition of cholinesterase occurs rapidly with 

recovery occurring within hours, the daily exposure to propoxur is the main duration of concern. 

Therefore, endpoints selected for short- and intermediate-terms routes of exposure are the same 

and intermediate-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 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. 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 manner specific to each application event. 

HED has determined that there is potential for short-term exposure through the dermal route of 

exposure in residential settings during the application of the pet collar 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 anticipated for the application 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 describe 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 frequented by the general population including outside of 

residential areas or within commercial and industrial areas. As a result, individuals can be 

exposed by entering these areas if they have been previously treated. The use of a propoxur pet 

collar can result in exposure through contact with a previously treated animal and is, therefore, 

subject to post-application assessment. 
Page 7 of 11 

A quantitative assessment of residential post-application 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 that were specific to the cumulative risk 

assessment, the propoxur pet collar dermal and incidental oral ingestion risk estimates were not 

of concern at that time. The current assessment is based on the anticipated exposure from the 

single chemical and risk and chemical specific toxicological information as described above. 

HED has determined that exposure to propoxur is likely following residential 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 ingestion exposure scenario using 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 Noncancer Exposure/Risk Estimates 

Adults and children in residential settings are likely to contact a pet previously treated with a 

propoxur pet collar and, therefore, risk estimates were calculated as appropriate for each. Adult 

exposures are limited to dermal post-application exposure for which no toxicological endpoint 

exists; therefore, exposure/risk was not estimated. 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 this route of exposure was not assessed; however, the incidental 

oral ingestion route of exposure was assessed for children. 

The Agency combines or aggregates risks resulting from exposures to individual chemicals when 

it is likely they can occur simultaneously based on the use pattern and the behavior associated 

with the exposed population. Children can be exposed to a previously treated dog through either 

dermal or incidental oral ingestion routes of exposure. These routes of exposure are typically 

aggregated; however, in the case of propoxur, dermal 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 adult and child exposure to propoxur pet collars. The assumptions 

and factors used in this risk assessment are consistent 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 Assessment for Children from 

Treated Pets). 

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

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

assessments to consider what is legally possible based on the label; 
Page 8 of 11 

• Pet collar products are intended to emit pesticide residues over extended periods of time 

to ensure a level of protection for the treated 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 thoroughly understood but it is clear that pet collar products must 

provide some level of efficacy over time, indicating that actual time-release emissions 

occur from the propoxur collars. Because little 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 initial placement on a pet. In order 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 period 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 application rate is available on the pet’s body and 

transferred to the adult/child as a transferable residue. This value is based on the 

professional judgment and experience of the OPP/HED staff from the review of data and 

is believed to be an upper-percentile 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 dogs 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., 

20cm2

/event) is placed in the mouth of the child contributing to incidental oral ingestion 

exposure. In the revised approach, the frequency 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 would result from petting/hugging. 

• Hand surface area per event is 20 cm2

, which represents the palmar surfaces of three 

fingers; 

• Saliva extraction efficiency is 50 percent meaning 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 cm2

, a child hug is 1875 cm2 

(US EPA, 1999 SAP). 
Page 9 of 11 

• HED’s default for the surface area of a treated pet is 5986 cm2

 (30 lb dog) and 2737 cm2

(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 assessment of residential post-application 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-mouth exposures that are 

attributable to a child touching a treated companion pet and then placing their hands in their 

mouth. 

 D (mg/kg/day) = TR * SAL * SAhands * 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/cm2

) 

SA hands = surface area of a child’s hands (20 cm2

) 

SAL = saliva extraction factor (50%) 

Freq = frequency of hand-to-mouth events (1 event/day) 

BW = child body weight (15 kg) 

TR (mg/cm2) = AR * FAR

 SA pet

 

Where: 

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

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

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

 SAPET = default surface area of a treated pet (5986 cm2

 dog and 2737 cm2 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 ingestion (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 and risk estimates for 20% transferability of 

residues over 15 day time period. This adjusted scenario results 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 

Amount1

(oz) 

Days SAPET

2

(cm2) 

Dose 

(mg/kg/day) 

NOAEL 

(mg/kg/day) 

LOC MOE 

Wellmark International3 

Dog Collar 5986 0.0063 44 

Cat Collar 1.5 15 2737 0.0138 0.28 1000 20 

Sergeant’s Pet Care Products, Inc4

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 maximum amount report for the labels. 

2. Surface area of the treated pet is calculated using the body 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, Inc pet collar products was provided 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 Group B2; “ Probable Human Carcinogenic ” and was assessed for 

carcinogenic risk from exposure using a linear, low dose extrapolation approach with a Q1* 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 greater 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 occurring in the United States from 2002 to the present. The 

IDS includes reports of incidents from registrant 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. Evaluation of the incident data is equivocal. It 
Page 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 effects due to the alleged exposure to the pesticide propoxur.