Date: 

Subject: 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

February 18, 2016 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

Pirimiphos-methyl. Draft Occupational and Residential Exposure/Risk 

Assessment for Registration Review. 

PC Code: I 08102 

Decision No.: 477390 

Petition No.: NA 

DP Barcode: 431439 

Registration No.: NA 

Regulatory Action: Registration Review 

Risk Assessment Type: Exposure Assessment Case No.: 2535 

TXRNo.: NA CAS No.: 29232-93-7 

MRIDNo.: NA 40 CFR: § 180.409 

From: 

Through: 

To: 

Introduction 

/ 

Z~ida Figueroa, DrPH, Industrial Hygienist ( L{-f/ l -·v----

R1sk Assessment Branch II ~ 

Health Effects Division (7509P) J ,: 

Christina Swartz, Branch Chief oJf-:.-.Af-----

Risk Assessment Branch II 

Health Effects Division (7509P) 

Russell Wasem and Neil Anderson 

Risk Management and Implementation Branch 1 

Pesticide Re-Evaluation Division (PRD) (7508P) 

The Pesticide Re-evaluation Division (PRD) requested that Health Effects Division (HED) 

conduct an occupational exposure/risk assessment to estimate the risk to human health that will 

result from the currently registered uses of pirimiphos-methyl. This memorandum contains 

HED's occupational/residential exposure and risk assessment required during registration review 

to reflect the updated pirimiphos-methyl's hazard assessment, science policies and procedures. 

There are no registered residential uses; therefore, this risk assessment only addresses potential 

occupational/commercial exposures associated with the pirimiphos-methyl's registered uses. 

Page I of22 
Page 2 of 22 

It is HED policy to use the best available data to assess exposure. Several sources of generic 

data were used in this assessment as surrogate data in the absence of chemical-specific data, 

including: Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the Agricultural 

Handler Exposure Task Force (AHETF) database; ExpoSAC Policy 9.1; ExpoSAC Policies 14, 

15, and 15.1 (SOPs for Seed Treatment). Some of these data are proprietary, and subject to the 

data protection provisions of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

Note: This memorandum was reviewed by the Exposure Science Advisory Committee 

(ExpoSAC) on July 31, 2014 and on December 21, 2015. 

 
Page 3 of 22 

 Table of Contents

1.0 Executive Summary ............................................................................................................. 4

2.0 Risk Assessment Conclusions and Recommendations ........................................................ 8

2.1 Summary of Risk Estimates ............................................................................................. 8

2.2 Label Recommendations from Occupational Assessment ............................................... 8

2.3 Label Recommendations from Residential Assessment .................................................. 8

2.4 Data Deficiencies and Requirements ............................................................................... 8

3.0 Hazard Characterization ....................................................................................................... 9

3.1 Acute Toxicity .................................................................................................................. 9

3.2 Toxicological PODs Used for Risk Assessment .............................................................. 9

4.0 Use Profile ......................................................................................................................... 11

5.0 Non-Occupational (Residential) Exposure and Risk Estimates ......................................... 13

5.1 Non-Occupational Spray Drift Exposure and Risk Estimates ....................................... 13

6.0 Occupational Exposure and Risk Estimates ...................................................................... 13

6.1 Occupational Handler Exposure/Risk Estimates............................................................ 13

6.2 Occupational Post-application Exposure/Risk Estimates ................................................... 21

6.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates ...................... 21

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates .......................... 21

Appendix A. Summary of Occupational Non-cancer Algorithms ............................................... 22
Page 4 of 22 

1.0 Executive Summary 

Pirimiphos-methyl (O-[2-diethylamino-6-methyl-4-pyrimidinyl] O,O-dimethyl 

phosphorothioate) is an organophosphate (OP) insecticide registered for post-harvest use on 

stored grains and grain seeds (corn and sorghum), for spray treatment of empty storage bins and 

as ready-to use (RTU) ear-tag treatment for livestock. 

This memorandum contains HED’s occupational/residential exposure and risk assessment 

required during registration review to reflect the updated pirimiphos-methyl’s hazard assessment, 

science policies and procedures. It addresses occupational handler exposure and risk associated 

with the registered uses of pirimiphos-methyl when used as directed. 

Exposure Profile 

Occupational workers may be exposed (dermal and inhalation routes) to pirimiphos-methyl 

during handling (mixing, loading, and/or applying) activities associated with RTU ear-tag 

treatments, spray or surface (“top-dressing by spraying on top of stored grain) treatments to 

stored grains/seeds and spray treatment of empty storage bins. Since the labels state that a spray 

solution could be applied uniformly as grain enters storage or export containers, a quantitative 

commercial seed treatment assessment (for primary and secondary handlers) was also conducted 

for stored grains/seeds (corn and sorghum). In general, occupational post-application exposures 

are not expected as reentry activities are not anticipated for the registered pirimiphos-methyl 

uses. 

 

Based on information provided by the registrant, Winfield Solutions, LLC, the major use of 

pirimiphos-methyl is for the post-harvest control of insects in grain and seeds going into storage 

or shipping containers in the South and warmer climates. It is applied at the point of transfer 

between August and September and the treated seed grain is usually stored for 8-9 months before 

planting (May). Currently, there are no residential uses of pirimiphos-methyl; therefore, 

exposure in non-occupational settings is not expected. Exposure via spray drift is not anticipated 

based on the current use pattern. 

Pirimiphos-methyl is a member of the OP class of pesticides. For OPs, matching the 

toxicological endpoint and the exposure duration is different than HED’s approach for 

conventional chemicals. OPs exhibit a phenomenon known as steady state acetylcholinesterase 

(AChE) inhibition. After repeated exposure at the same dose, the degree of inhibition comes into 

equilibrium with the production of new, uninhibited enzyme. The steady state approach is 

appropriate for pirimiphos-methyl given the toxicological and exposure profile. The “steady 

state” endpoint selection for pirimiphos-methyl overlaps with HED’s traditional short-term 

exposure duration endpoint selection and is considered health protective for occupational 

handlers that apply pirimiphos-methyl commercially over longer periods of time (i.e., 

intermediate-term exposures). 

Hazard Profile 

HED has determined that the toxicology database for pirimiphos-methyl is complete and 

adequate for risk assessment. Pirimiphos-methyl has low toxicity (Toxicity Category III) via 
Page 5 of 22 

oral, dermal, and inhalation routes of exposure. It is an eye irritant (Toxicity Category II) and 

moderate dermal irritant (Toxicity Category III); it is not a dermal sensitizer. 

Like other OPs, the initiating event in the adverse outcome pathway (AOP), also often called the 

mode of action (MOA), for pirimiphos-methyl involves inhibition of the enzyme AChE via 

phosphorylation of the serine residue at the active site of the enzyme. This inhibition leads to 

accumulation of acetylcholine and ultimately to neurotoxicity in the central and/or peripheral 

nervous system. For pirimiphos-methyl, AChE inhibition is the most sensitive endpoint in the 

toxicology database in multiple species, durations, lifestages, and routes. Clinical signs of 

neurotoxicity can be found throughout the pirimiphos-methyl toxicology database at doses much 

higher than those causing inhibition of AChE. 

None of the guideline developmental and reproduction toxicity studies for pirimiphos-methyl 

demonstrated quantitative and/or qualitative susceptibility. However, in the acute comparative 

CCA study, pups were more sensitive than adult animals to AChE inhibition. In the repeat 

comparative CCA study, adult and pup AChE inhibition were generally comparable. The 

available CCA studies for pirimiphos-methyl do not contain a gestational component and a DNT 

study is not available. Therefore, no AChE data are available for comparative AChE evaluation 

of pregnant dams and fetuses. 

The points of departure (PoD) selected are based on the most sensitive endpoint red blood cell 

(RBC) acetylcholinesterase (AChE) inhibition and are protective of the clinical signs 

(neurotoxicity) observed in the toxicology database. 

For steady state dermal risk assessment, a no observed adverse effects level (NOAEL) of 25 

mg/kg/day was selected based on decreased RBC AChE inhibition from a 21- day dermal rat 

toxicity study that contains AChE inhibition data. Since the steady state dermal PoD was based 

on a route-specific toxicity study, an absorption factor was not necessary to estimate dermal 

exposure. Inhalation AChE data are not available for pirimiphos-methyl; therefore, an oral study 

was used for endpoint selection. For inhalation risk assessment, an inhalation PoD was selected 

from a repeat comparative cholinesterase study based on RBC AChE inhibition in pups 

(Benchmark Dose Level (BMDL10) = 0.73 mg/kg/day or 0.00062 mg/L/day; Benchmark Dose 

(BMD10) = 1.01 mg/kg/day). Since the NOAEL for inhalation risk assessment was chosen from 

an oral study, it was assumed that toxicity via the inhalation route is equivalent to oral toxicity. 

HED has determined that a subchronic inhalation study is now required for pirimiphos-methyl 

(HASPOC, TXR # 0053947). 

The level of concern (LOC) for occupational dermal exposure is equal to a margin of exposure 

(MOE) of 1,000 (10X to account for interspecies extrapolation, 10X for intraspecies variation, 

and 10X for FQPA SF due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects and the lack of gestational data). The LOC for inhalation exposure 

is 3,000X (10X for interspecies extrapolation, 10X for intraspecies variation, and 30X database 

uncertainty factor incorporating uncertainty in the human dose-response relationship for 

neurodevelopmental effects, lack of gestational component, and absence of the inhalation study). 

 
Page 6 of 22 

For pirimiphos-methyl, the risk assessment for inhalation exposure is based on RBC AChE 

inhibition. For dermal exposure, an endpoint was not identified for the dermal study used for 

risk assessment, as no treatment related effects were seen at doses up to the highest dose tested 

(HDT) of 25 mg/kg/day. However, since the dermal study did not test up to the limit dose, there 

is potential for treatment related effects on AChE inhibition at higher doses. Therefore, dermal 

and inhalation routes can be combined. The inhalation and dermal routes have different LOCs; 

therefore, in order to combine exposure from both routes, the aggregate risk index (ARI) is used 

to estimate exposure and risk. ARIs ≥ 1 are not of concern. 

Pirimiphos-methyl is classified as “not likely to be carcinogenic to humans.” Treatment-related 

increase in tumors was not observed in carcinogenicity studies in rats and mice and there is no 

concern for mutagenicity. 

Residential Exposure 

There are no registered residential uses, or commercial/professional uses at residential sites 

associated with pirimiphos-methyl at this time. Residential exposures are not expected from the 

current uses; therefore, a quantitative residential handler and post-application assessment was not 

conducted. 

Spray Drift 

HED determined that pirimiphos-methyl is not registered on use sites that are likely to result in 

spray drift. Therefore, a quantitative spray drift assessment was not conducted for pirimiphosmethyl. 

Occupational Handler Exposure 

Generic, surrogate handler data were used in the assessment. A female body weight of 69 kg 

was assumed to account for potentially pregnant workers. Dermal and inhalation risk estimates 

were combined for risk assessment because effects on AChE inhibition were observed in both 

routes. Since the inhalation and dermal routes have different LOCs, the aggregate risk index 

(ARI) is used to estimate exposure and risk. ARIs ≥ 1 are not of concern. 

Impregnated ear-tag: Negligible dermal and inhalation exposures are expected for workers 

applying RTU impregnated ear-tag to cattle with use of label required personal protective 

equipment or PPE (i.e., chemical-resistant gloves); therefore, no risks of concern are expected. 

Stored grains/seeds and empty storage bins: Steady state dermal and inhalation exposures and 

risks were calculated for occupational handlers for the registered use on stored grain/seeds or in 

empty grain storage bins. Pirimiphos-methyl may be applied to grain with handheld equipment 

as a surface spray to control insects. It may be applied via handheld equipment to empty storage 

bins. 

Risk concerns were identified for all handler scenarios (mixer/loader/applicator) using handheld 

equipment (i.e., manually-pressurized handwand and backpack sprayer) when treating stored 

grain/seeds as a surface spray (“top-dressing”) using label-required clothing (e.g., long-sleeved 

shirt, long pants, shoes plus socks) and PPE (i.e., chemical-resistant gloves and protective 

eyewear). Risks for manually-pressurized handwand obtained an ARI=1.0 when using label-
Page 7 of 22 

required clothing and PPE plus a PF10 respirator. Risks for backpack sprayer treatments remain 

of concern (ARI=0.39) despite consideration of additional levels of PPE (e.g., double layer 

clothing and PF10 respirator). 

The product label EPA Reg No. 1381-170 is unclear about the potential treatment of empty 

storage bins. Therefore, this assessment quantitatively calculates risk estimates using handheld 

equipment (i.e., mechanically-pressurized handgun, manually-pressurized handwand and 

backpack sprayer) to treat empty storage bins. Risk concerns were identified for all handler 

scenarios. Total ARIs range from 0.001-0.09 for mixers/loaders/applicators treating empty 

storage bins using handheld equipment. Risks for these scenarios remain of concern despite 

consideration of additional PPE (e.g., double layer clothing and PF10 respirator). 

Seed Treatment Assessment: All risk estimates for commercial seed treatment handlers were not 

of concern (i.e., MOEs ≥ 1,000 for dermal and MOEs ≥ 3,000 for inhalation) when wearing 

single layer clothing + gloves for loader/applicator and multiple activities worker; and single 

layer clothing + no gloves for sewer and bagger. All Total ARIs are greater than 1 and therefore, 

are not of concern. 

Occupational Post-application Exposure 

Post-application exposure from treated stored grains/seeds is unlikely because sustained levels of 

contact with treated stored grain/seed after application is not expected. Commercial applicators 

rarely have direct contact with the stored grain during testing of grain, maintenance, or other 

intermittent activities. Therefore, post-application exposure is expected to be negligible and a 

quantitative post-application assessment was not required for pirimiphos-methyl from treated 

stored grains/seeds. 

Also, post-application exposures are not expected for workers removing ear-tags from treated 

cattle. No REI is listed on the available product label as the label-defined use sites are not 

subject to the Worker Protection Standard (WPS). 

Human Studies Review 

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

PHED 1.1; the AHETF database; ExpoSAC Policy 14 (SOPs for Seed Treatment); these studies 

are: (1) subject to ethics review pursuant to 40 CFR 26, (2) have received that review, and (3) are 

compliant with applicable ethics requirements. For certain studies, the ethics review may have 

included review by the Human Studies Review Board. Descriptions of data sources, as well as 

guidance on their use, can be found at the Agency website1

. 

 

1

 Available at: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handlerexposure-data and http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-postapplication-exposure.
Page 8 of 22 

2.0 Risk Assessment Conclusions and Recommendations 

2.1 Summary of Risk Estimates 

There are no risks of concern for workers applying RTU impregnated ear-tag to cattle with use of 

label required personal protective equipment or PPE (i.e., chemical-resistant gloves). In 

addition, all risk estimates for commercial seed treatment handlers were not of concern. 

However, there are risk of concern for occupational handlers when mixing/loading/applying 

pirimiphos-methyl when using handheld equipment. Based on the occupational risk estimates, 

additional PPE will be needed in the registered labels. Detailed risk estimates description is 

available in Section 6.0. 

2.2 Label Recommendations from Occupational Assessment 

Based on the occupational risk estimates, additional PPE will be needed on the registered labels 

to protect occupational handlers when mixing/loading/applying pirimiphos-methyl during spray 

or surface (“top-dressing”) treatments using manually-pressurized handwand (i.e., PF 10 

respirator). Risks for backpack sprayer treatments remain of concern (ARI=0.39) despite 

consideration of additional levels of PPE (e.g., double layer clothing and PF10 respirator). 

The registered label EPA Reg No. 1381-170 is unclear about the potential treatment of empty 

storage bins. This assessment quantitatively calculates risk estimates for empty storage bins 

treatment using handheld equipment (i.e., mechanically-pressurized handgun, manuallypressurized handwand and backpack sprayer). If the label is clarified about the potential 

treatment of empty storage bins, that scenario will not be applicable and the occupational risk 

estimates for that scenario will not be applicable for risk assessment. 

2.3 Label Recommendations from Residential Assessment 

None. 

2.4 Data Deficiencies and Requirements 

None. 
Page 9 of 22 

3.0 Hazard Characterization 

The toxicology database for pirimiphos-methyl is adequate for risk assessment. Pirimiphosmethyl is a member of the organophosphate (OP) class of pesticides. Like other OPs, the 

initiating event in the adverse outcome pathway (AOP)/mode of action (MOA), for pirimiphosmethyl involves inhibition of the enzyme AChE via phosphorylation of the serine residue at the 

active site of the enzyme. This inhibition leads to accumulation of acetylcholine and ultimately 

to neurotoxicity in the central and/or peripheral nervous system and is the endpoint of concern. 

Cholinesterase inhibition is the endpoint of concern for pirimiphos-methyl. 

3.1 Acute Toxicity 

Pirimiphos-methyl has low toxicity (Toxicity Category III) via oral, dermal, and inhalation 

routes of exposure. It is an eye irritant (Toxicity Category II) and moderate dermal irritant 

(Toxicity Category III); it is not a dermal sensitizer. The acute toxicity for pirimiphos-methyl is 

summarized in Table 3.1. 

Table 3.1. Acute Toxicity Studies for Pirimiphos-methyl. 

Guideline No./Study Type MRID No. Results Toxicity 

Category 

870.1100 Acute oral toxicity (rat) 00126257 LD50 =2.4 g/kg III 

870.1200b Acute dermal toxicity (rabbit) 00126257 LD50 = M: 2.2-3.5 g/kg 

 F: >3.5 g/kg 

III 

870.1300 Acute inhalation toxicity (rat) 41556304 LC50 >4.7 mg/L IV 

870.2400 Acute eye irritation (rabbit) 00126257 Irritant II 

870.2500 Acute dermal irritation (rabbit) 00126257 Moderate Irritant III 

870.2600 Skin sensitization (guinea pig) 00126257 Non-sensitizer NA 

NA = Not applicable.

3.2 Toxicological PODs Used for Risk Assessment 

For risk assessment, a 21- day dermal rat toxicity study, with a NOAEL of 25 mg/kg/day, was 

selected for dermal exposure. However, an endpoint was not determined for the study since no 

treatment-related effects were observed at any dose. The study is appropriate for the route and 

duration of exposure; there is no concern for increased sensitivity after repeated exposure. 

Since inhalation AChE data are not available for pirimiphos-methyl, an oral study was used for 

endpoint selection. A steady state inhalation PoD was selected from the repeat comparative 

cholinesterase study based on RBC AChE inhibition in pups (BMDL10 = 0.73 mg/kg/day or 

0.00062 mg/L/day; BMD10 = 1.01 mg/kg/day). HED determined that a subchronic inhalation 

study is required for pirimiphos-methyl. 

The level of concern (LOC) for occupational dermal exposure is equal to a margin of exposure 

(MOE) of 1,000 (10X to account for interspecies extrapolation, 10X for intraspecies variation, 
Page 10 of 22 

and 10X for FQPA SF due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects and the lack of gestational data). The LOC for inhalation exposure 

is 3,000 (10X for interspecies extrapolation, 10X for intraspecies variation, and 30X database 

uncertainty factor incorporating uncertainty in the human dose-response relationship for 

neurodevelopmental effects, lack of gestational component, and absence of the inhalation study). 

For pirimiphos-methyl, the risk assessment for inhalation exposure is based on RBC AChE 

inhibition. For dermal exposure, an endpoint was not identified for the dermal study used for 

risk assessment, as no treatment related effects were seen at doses up to the highest dose tested 

(HDT) of 25 mg/kg/day. However, since the dermal study did not test up to the limit dose, there 

is potential for treatment related effects on AChE inhibition at higher doses. Therefore, dermal 

and inhalation routes can be combined. The inhalation and dermal routes have different LOCs; 

therefore, in order to combine exposure from both routes, the aggregate risk index (ARI) is used 

to estimate exposure and risk. ARIs ≥ 1 are not of concern. 

Pirimiphos-methyl is classified as “not likely to be carcinogenic to humans.” No treatmentrelated increase in tumors was observed in carcinogenicity studies in rats and mice. 

Additionally, there is no concern for mutagenicity. 

Table 3.2. Summary of Toxicological Doses and Endpoints for Pirimiphos-methyl for Use in Occupational 

Human Health Risk Assessments. 

Exposure/ 

Scenario 

Point of 

Departure 

Uncertainty/FQP

A Factors 

Level of Concern 

for Risk 

Assessment 

Study and Toxicological Effects 

Dermal 

Steady State 

(21 days and 

longer) 

NOAEL = 

25 mg/kg/day 

UFA = 10x 

UFH = 10x 

UFDB = 10x 

(covers epi, 

gestational) 

Occupational 

LOC=1,000 

21-day dermal toxicity study 

(MRID 45764501) in rats 

LOAEL= not determined 

Inhalation 

Steady State 

(21 days and 

longer) 

BMDL10 = 

0.73 

mg/kg/day 

UFA = 10x 

UFH = 10x 

UFDB = 30x 

(covers epi, 

gestational, and 

inhalation) 

Occupational 

LOC=3,000 

Repeat CCA Study (MRID 

49037406) in the rat 

BMD10 = 1.01mg/kg/day 

Inhibition of RBC AChE in pups 

on PND 21 

Cancer (oral, 

dermal, 

inhalation) 

Classification: Classification: "Not likely to be carcinogenic to humans.” 

Point of Departure (PoD) = A data point or an estimated point that is derived from observed dose-response data and 

used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human 

exposures. NOAEL = no observed adverse effect level. LOAEL = lowest observed adverse effect level. UF = 

uncertainty factor. UFA = extrapolation from animal to human (interspecies). UFH = potential variation in 

sensitivity among members of the human population (intraspecies). UFDB=database uncertainty factor. MOE = 

margin of exposure. LOC = level of concern. N/A = not applicable. BMDL = benchmark dose level. BMD = 

benchmark dose.
Page 11 of 22 

Absorption: Since the dermal PoDs were based on route-specific toxicity studies, no absorption 

factors were necessary to estimate dermal exposure. Furthermore, no inhalation absorption data 

are available; therefore, toxicity by the inhalation route is considered to be equivalent to the 

estimated toxicity by the oral route of exposure. 

Body Weight: For adults, when an endpoint is not sex-specific (i.e., the endpoints are based on 

developmental or fetal effects) a body weight of 80 kg is typically used in risk assessment; 

however, in this case, a female-specific body weight of 69 kg was used. While the endpoint of 

concern, RBC AChE inhibition, is not sex-specific, the female-specific body weight was used to 

protect for pregnant women due to uncertainty in the human dose-response relationship for 

neurodevelopmental effects. 

4.0 Use Profile 

Pirimiphos-methyl is registered as a post-harvest treatment to control insects on stored grain and 

seeds going into storage or shipping containers or to treat empty grain bins where grain is stored. 

There were also two special local need labels registered for the use of pirimiphos-methyl on iris 

and gladiolas bulbs in Washington state and Michigan state. Both labels were cancelled or the 

registration has been expired. Currently, there are no registered uses of pirimiphos-methyl that 

could result in residential exposure. 

 

The pirimiphos-methyl is also registered for ear-tag treatment of livestock (Dominator® 

Insecticide Ear Tag [EPA Reg. No. 773-68] and Double Barrel® VP Insecticide Ear Tag [EPA 

Reg. No. 773-81]) and the labels direct handlers to wear long-sleeved shirt and long pants, shoes 

plus socks, and chemical-resistant gloves. 

The registered product labels Actellic® 5E Insecticide [EPA Reg. No. 1381-170] and Executive 

S-PTM Insecticide Emulsifiable Concentrate [EPA Reg. No. 1381-198] direct mixers, loaders, and 

other handlers to wear long-sleeved shirt and long pants, shoes plus socks, chemical-resistant 

gloves and protective eyewear. All other mixers, loaders, applicators and other handlers must 

wear: coveralls over long-sleeved shirt and long pants, chemical-resistant footwear plus socks, 

chemical-resistant gloves and protective eyewear. In addition, mixers and loaders must wear a 

chemical-resistant apron. 

The use directions of the pirimiphos-methyl products are summarized in Table 4.0. 

 
Page 12 of 22 

Table 4.0. Summary of Directions for Use of Pirimiphos-methyl. 

Applic. Timing, 

Type, and Equip. 

Formulation 

[EPA Reg. No.] 

Max. Single 

Applic. Rate 

Max. No. 

Applic. per 

Season 

Max. 

Seasonal 

Applic. 

Rate 

(lb ai/A) 

PHI 

(days) 

Use Directions and 

Limitations 

Cattle Ear Tags 

Animal treatment; 

Impregnated material 

(controlled release). 

Dominator®

Insecticide Ear Tag 

(20% ai) 

[EPA Reg. No. 773-

68] 

2 ear tags/animal 

(9.6 g/tag or 1.92 g 

ai/tag) 

1 appl. /year N/A N/A 

Apply when flies appear in 

Spring. Effective for 5 

months, remove in fall. 

Apply with ALLFLEX 

Animal treatment; Tagging System. 

Impregnated material 

(controlled release). 

Double Barrel® VP 

Insecticide EarTag 

(14% ai) 

[EPA Reg. No. 773-

81]1

2 ear tags/animal 

(9.5 g/tag or 1.92 g 

ai/tag) 

1 appl./year N/A N/A 

Stored Corn (field and pop); Grain Sorghum (including bulk and bagged seed) 

Spray treatment using 

large tanks as grain 

enters storage or 

export containers. Actellic® 5E 

Insecticide 

Water Soluble 

Packets 

(WPS)/Emulsifiable 

Concentrate (EC)3

(57% ai) 

(5 lb ai/gal) 

[EPA Reg. No. 

1381-170] 

12.3 fl.oz/30 tons of 

grain equivalent to 

0.016 lb ai/ton of 

grain, 

0.000008 lb ai/lb of 

seed 1 appl./stored 

crop 

N/A N/A 

Treated seed for planting at 

point of transfer (8-9 months 

before planting). Treatment 

is only off-farm (or in a 

facility were the seed is 

bagged). 

Surface treatment (or 

“top dressing”) by 

spraying on top of 

stored grain. 

Handheld sprayers. 

0.12 lb ai /1,000 ft2

of surface area 

Apply as a split treatment 

before and after raking. 

Empty bins spray 

treatment. Handheld 

sprayers. 

0.059 lb ai/gal 1 appl./bin N/A N/A 

Apply to clean and treat 

empty storage bins prior to 

storage of seeds. 

Spray treatment as 

grain enters storage 

or export containers.

Executive S-PTM 

Insecticide 

Emulsifiable 

Concentrate 

(57% ai) 

(5 lb ai/gal) 

[EPA Reg. No. 

1381-198]2

0.0078 lb ai/ton of 

grain; 0.0000039 lb 

ai/lb of grain 

1 appl./stored 

crop 

N/A N/A 

Treated seed for planting at 

point of transfer (8-9 months 

before planting). Treatment 

of seed is off-farm in a 

facility where seed is 

bagged. Do not use as a “top 

dressing” treatment. Product 

not for use as a seed 

treatment to control insects. 

No bins treatment; always 

start with clean storage bins. 

1. Mixture with lambda-cyhalothrin 6.8%.

2. Double pack with Spinosad (EPA Reg. No. 62719-294 (22.8% ai or 2 lb spinosad technical/gal). The two products are mixed at the time of 

treatment (i.e., “admixture”). 

3. Statements on product label: 1) For the product label Actellic® 5E Insecticide [EPA Reg. No. 1381-170], the EC formulation is to be used with 

a closed system/loading system designed by the manufacturer to prevent pesticide from contacting handlers. This product is formulated in a 

container designed for closed mixing and loading. 2) For the product Actellic® 5E Insecticide [EPA Reg. No. 1381-170] when packaged in water 

soluble packets (WSP), when used correctly, qualify as a closed mixing/loading system under the description of 40 CFR 170.240(d)(4). Mixers 

and loaders using water soluble packets must wear the PPE required for mixers/loaders, and must be provided, must have immediately available 

and must use in an emergency (such as a broken package, spill or equipment breakdown) the following PPE: coveralls and chemical-resistant 

footwear. 
Page 13 of 22 

5.0 Non-Occupational (Residential) Exposure and Risk Estimates 

There are no registered residential uses, or commercial/professional uses at residential sites 

associated with pirimiphos-methyl at this time. Therefore, a quantitative residential exposure 

assessment is not required. 

5.1 Non-Occupational Spray Drift Exposure and Risk Estimates 

All the pirimiphos-methyl uses were evaluated as part of the Registration Review process to 

ensure that the potential for spray drift from all registered uses have been considered in the risk 

assessment. Based on the use-pattern, HED determined that pirimiphos-methyl is not registered 

on use sites or applied via equipment or methods that would result in spray drift. Therefore, a 

quantitative spray drift assessment was not conducted for pirimiphos-methyl. 

6.0 Occupational Exposure and Risk Estimates 

6.1 Occupational Handler Exposure/Risk Estimates 

HED uses the term handlers to describe those individuals who are involved in the pesticide 

application process. HED believes that there are distinct job functions or tasks related to 

applications and exposures can vary depending on the specifics of each task. Job requirements 

(amount of chemical used in each application), the kinds of equipment used, the target being 

treated, and the level of PPE protection used by a handler can cause exposure levels to differ in a 

manner specific to each application event. 

Pirimiphos-methyl is currently registered for use on impregnated ear tags for cattle, as a postharvest treatment to control of insects on stored grains as a surface spray (or “top-dressing”) 

using handheld equipment. Also, grain storage workers may apply liquid pirimiphos-methyl to 

the walls of empty grain storage bins using handheld sprayers. Since the labels state that the 

products could be use in off-farm facilities and that a spray solution could be applied uniformly 

as grain enters storage or export containers, a quantitative commercial seed treatment assessment 

(for primary and secondary handlers) was also conducted for stored grains/seeds (corn and 

sorghum). Both labels state that the products are not intended for use to control of soil insects. 

Based on the anticipated use patterns and current labeling, types of equipment and techniques 

that can potentially be used, occupational handler exposure is expected from the registered uses. 

The quantitative exposure/risk assessment developed for occupational handlers is based on the 

following scenarios: 

 Applicator of RTU (impregnated) ear tags; 

 Mixing/Loading/Applying Liquids using Manually-pressurized Handwand Equipment for 

Empty Storage Bins Treatment Applications; 

 Mixing/Loading/Applying Liquids using Backpack Sprayer Equipment for Empty 

Storage Bins Treatment Applications; 

 Mixing/Loading/Applying Liquids using Mechanically-pressurized Handgun Equipment 
Page 14 of 22 

for Empty Storage Bins Treatment Applications; 

 Mixing/Loading/Applying Liquids using Manually-pressurized Handwand Equipment for 

Spray or Surface (“Top-dressing”) Treatment Applications on Stored Grains or Seeds; 

 Mixing/Loading/Applying Liquids using Backpack Sprayer Equipment for Spray or 

Surface (“Top-dressing”) Treatment Applications on Stored Grains or Seeds; 

 Primary Handler Seed Treatment Scenarios (i.e., activities associated to treating the 

seed); and 

 Secondary Handler Seed Treatment Scenarios (i.e., activities associated with planting 

treated seed). 

No mechanically-pressurized handgun equipment was assessed for surface spray (or “Topdressing”) treatment applications on stored grains/seeds, because the equipment (hand-gun 

sprayer) is not suitable (i.e., to treat a thin layer of solution on stored grains/seeds) for that 

scenario. 

Primary Handler (Treating Seed) 

Potential primary occupational handler exposure scenarios from the use of pirimiphos-methyl as 

a commercial seed treatment include: 

 Mixing, loading, applying liquid formulations; 

 Bagging treated seed; 

 Sewing bags; and 

 Multiple activities. 

Typically, for large-scale commercial seed treatments, workers perform only those specific 

individual tasks listed above; however, it is assumed that workers also may perform multiple 

activities throughout the day. As a result a “multiple activities” scenario (i.e., where one worker 

performs all seed treatment tasks such as loading/applying, sewing, bagging, cleaning, 

calibration, repair, forklift driver, etc.) was addressed. Furthermore, the grain is treated only 

once with pirimiphos-methyl; however, repeat treatment of grain by workers at storage silos and 

shipping ports may result in repeated worker exposures. 

Secondary Handler (Planting Treated Seed) 

Potential secondary occupational handler exposure scenarios from the use of pirimiphos-methyl 

as a commercial seed treatment include planting treated seed. 

It is the policy of HED to use the best available data to assess handler exposure. Sources of 

generic handler data for seed treatment are incorporated in HED ExpoSAC Policy 14: SOPs for 

Seed Treatment. The amount of active ingredient handled depends on the application rate (lb 

ai/lb seed or lb ai/seed), the pounds of seed treated in a day, and the pounds of seed that can be 

planted in a day, all of which vary depending upon the seed type. Values for the amount of seed 

treated and planted per day were obtained from HED ExpoSAC Policy 15.1: Interim Guidance – 

Amount of Commercial Seed per Day and the Biological and Economic Analysis Division 
Page 15 of 22 

(BEAD) memo: “Acres Planted per Day and Seeding Rates of Crops Grown in the United 

States.” (J. Becker, March 2011). 

Occupational Handler Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the occupational 

handler risk assessments. Each assumption and factor is detailed below on an individual basis.

Application Rate: The maximum single application rates on the registered labels were used to 

assess the handler exposure scenarios. Refer to Table 4.0 for a complete use pattern description. 

Unit Exposures: It is the policy of HED to use the best available data to assess handler exposure. 

Sources of generic handler data, used as surrogate data in the absence of chemical-specific data, 

include PHED 1.1, the AHETF database, and ExpoSAC Policy 14 for Seed Treatment, or other 

registrant-submitted occupational exposure studies. Some of these data are proprietary (e.g., 

AHETF data), and subject to the data protection provisions of FIFRA. The standard values 

recommended for use in predicting handler exposure that are used in this assessment, known as 

“unit exposures”, are outlined in the “Occupational Pesticide Handler Unit Exposure Surrogate 

Reference Table2

”, which, along with additional information on HED policy on use of surrogate 

data, including descriptions of the various sources, can be found at the Agency website3. 

Amount Handled: The amount handled is based on the specifications on the registered labels and 

guidance in ExpoSAC Policy 9.1, Policy 15.1: Interim Guidance – Amount of Commercial Seed 

per Day and the BEAD memo “Acres Planted Per Day and Seeding Rates of Crops Grown in the 

United States” (J. Becker, March 2011). 

Exposure Duration: HED classifies exposures from 1 to 30 days as short-term and exposures 30 

days to six months as intermediate-term. Exposure duration is determined by many things, 

including the exposed population, the use site, the pest pressure triggering the use of the 

pesticide, and the cultural practices surrounding that use site. For the OP pesticides, the match 

between the toxicological endpoint selection and the exposure duration is different than HED’s 

approach for conventional chemicals. The endpoint selection for OP pesticides involves a 

“single day” and “steady state” approach based on an individual chemical’s cholinesterase 

inhibition. The steady state approach is appropriate for pirimiphos-methyl given the 

toxicological and exposure profile. The “steady state” endpoint selection for pirimiphos-methyl 

overlaps HED’s traditional short-term exposure duration endpoint selection and is considered 

health protective for occupational handlers that apply commercially over longer periods of time 

(i.e., intermediate-term exposures). 

Based on the anticipated use patterns and current labeling, types of equipment and techniques 

that can potentially be used, steady state exposures are expected for occupational handlers. The 

steady state toxicological endpoints can be found in Table 3.2. 

 

2

 Available at: http://www2.epa.gov/sites/production/files/2015-09/documents/handler-exposure-table-2015.pdf. 3

 Available at: http://www2.epa.gov/pesticide-science-and-assessing-pesticide-risks/occupational-pesticide-handlerexposure-data. 
Page 16 of 22 

Mitigation/Personal Protective Equipment: Estimates of dermal and inhalation exposure were 

calculated for various levels of PPE depending on the scenario. The pirimiphos-methyl 

registered products for ear-tag treatment of livestock (Dominator® Insecticide Ear Tag [EPA 

Reg. No. 773-68] and Double Barrel® VP Insecticide Ear Tag [EPA Reg. No. 773-81]) direct 

handlers to wear baseline clothing (i.e., long-sleeved shirt and long pants, shoes plus socks) and 

chemical-resistant gloves. The pirimiphos-methyl product labels Actellic® 5E Insecticide [EPA 

Reg. No. 1381-170] and Executive S-PTM Insecticide Emulsifiable Concentrate [EPA Reg. No. 

1381-198] direct mixers, loaders, and other handlers to wear baseline clothing, chemical-resistant 

gloves and protective eyewear. All other mixers, loaders, applicators and other handlers must 

wear: coveralls over long-sleeved shirt and long pants, chemical-resistant footwear plus socks, 

chemical-resistant gloves and protective eyewear. In addition, mixers and loaders must wear a 

chemical-resistant apron. 

Occupational Handler Non-Cancer Exposure and Risk Estimate Equations 

The algorithms used to estimate non-cancer exposure and dose for occupational handlers can be 

found in Appendix A. 

Combining Exposures/Risk Estimates

A total aggregated risk index (ARI) was used since the LOC values for dermal exposure (1,000) 

and inhalation exposure (3,000) are different. The target ARI is 1; therefore, ARIs of less than 1 

are risk estimates of concern. The aggregate risk index (ARI) was calculated as follows: 

Aggregate Risk Index (ARI) = 1÷ [(Dermal LOC ÷ Dermal MOE)+ (Inhalation LOC ÷ Inhalation MOE)] 

Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates 

Tables 6.1a and b present the estimated steady state dermal and inhalation risk estimates for 

occupational handlers. Dermal and inhalation risk estimates were combined for risk assessment 

because effects on AChE inhibition were observed in both routes. Since the inhalation and 

dermal routes have different LOCs, the aggregate risk index (ARI) is used to estimate exposure 

and risk. ARIs ≥ 1 are not of concern. 

Impregnated ear-tag: Negligible dermal and inhalation exposures are expected for workers 

applying RTU impregnated ear-tag to cattle with use of label required personal protective 

equipment or PPE (i.e., chemical-resistant gloves); therefore, no risks of concern are expected. 

Stored grains/seeds and empty storage bins: Steady state dermal and inhalation exposures and 

risks were calculated for occupational handlers for the registered use on stored grain/seeds or in 

empty grain storage bins. Pirimiphos-methyl may be applied to grain with handheld equipment 

as a surface spray to control insects. It may be applied via handheld equipment to empty storage 

bins. 

Risk concerns were identified for all handler scenarios (mixer/loader/applicator) using handheld 

equipment (i.e., manually-pressurized handwand and backpack sprayer) when treating stored 

grain/seeds as a surface spray (“top-dressing”) using label-required clothing (e.g., long-sleeved 

shirt, long pants, shoes plus socks) and PPE (i.e., chemical-resistant gloves and protective 
Page 17 of 22 

eyewear). Risks for manually-pressurized handwand obtained an ARI=1.0 when using labelrequired clothing and PPE in addition to a PF10 respirator. Risks for backpack sprayer 

treatments remain of concern (ARI=0.39) despite consideration of additional levels of PPE (e.g., 

double layer clothing and PF10 respirator). 

The product label EPA Reg No. 1381-170 is unclear about the potential treatment of empty 

storage bins. Therefore, this assessment quantitatively calculates risk estimates using handheld 

equipment (i.e., mechanically-pressurized handgun, manually-pressurized handwand and 

backpack sprayer) to treat empty storage bins. Risk concerns were identified for all handler 

scenarios. Total ARIs range from 0.001-0.09 for mixers/loaders/applicators treating empty 

storage bins using handheld equipment. Risks for these scenarios remain of concern despite 

consideration of additional PPE (e.g., double layer clothing and PF10 respirator). 

Seed Treatment Assessment: All risk estimates for commercial seed treatment handlers were not 

of concern (i.e., MOEs ≥ 1,000 for dermal and MOEs ≥ 3,000 for inhalation) when wearing 

single layer clothing + gloves for loader/applicator and multiple activities worker; and single 

layer clothing + no gloves for sewer and bagger. All Total ARIs are greater than 1 and therefore, 

are not of concern. 

Seed Treatment 

Steady state risk estimates for commercial seed treatment (primary and secondary handlers) are 

presented in Table 6.1b. All MOEs calculated for commercial seed treatment handlers (i.e., 

loader/applicator, sewer, bagger, and multiple activities seed treatment workers) are greater than 

the LOCs (Dermal LOC=1,000 and Inhalation LOC=3,000). All ARIs are greater than 1 and not 

of concern for workers wearing single layer clothing + gloves for loader/applicator and multiple 

activities worker; and single layer clothing + no gloves for sewer and bagger. The lowest ARI 

was 3 for workers conducting multiple activities (primary handlers).
Page 18 of 22 

Table 6.1a. Occupational Handler Exposure and Risk Estimates for Pirimiphos-methyl. Exposure Scenario and Product 

Target Site 

Application Ratea

Amount Handled 

Dermal Unit Exposureb(mg/lb) [Mitigation Level]

Inhalation Unit Exposureb(mg/lb) [Mitigation Level] 

Dermal Dosec (mg/kg/day) 

Dermal MOEdLOC = 1,000 

Inhalation Dosee (mg/kg/day) 

InhMOLO3,0

Applicator 

RTU Impregnatedmaterial Tag Eartag (Cattle) 1.92 g ai/tag 

200 

cattle/day 

at 2 tags 

per cattle 

No data No data Negligible. PPE required on label include che

handlers. 

Mixer/Loader/Applicator 

Sprays using Manuallypressurized Handwand 

Empty Storage Bin Treatment 

0.059 lb 

ai/gal 500 gal 

100 

[Baseline; No-G] 

0.030 

[No-R] 42.8 0.58 0.01280 

0.430 

[Baseline; G] 

0.006 

[PF5] 0.184 140 0.00257 

0.365 

[DL-G] 

0.003 

[PF10] 0.157 160 0.00128 

Sprays using Mechanicallypressurized Handgun 

0.059 lb 

ai/gal 500 gal 

1.8 

[Baseline; No-G] 

0.079 

[No-R] 0.770 30 0.0338 

0.640 

[Baseline; G] 

0.0158 

[PF5] 0.274 90 0.00675 

0.365 

[DL-G] 

0.0079 

[PF10] 0.157 160 0.00338 

Sprays using Backpack Sprayer 

0.059 lb 

ai/gal 500 gal 

2.50 

[Baseline; G] 

0.030 

[No-R] 1.1 23 0.0128 

1.6 

[DL-G] 

0.006 

[PF5] 0.684 37 0.00257 

1.6 

[DL-G] 

0.003 

[PF10] 0.684 37 0.00128 

Sprays using Manuallypressurized Handwand 

Spray or Surface (Topdressing) Appl. on Stored Grain or Seed 

0.059 lb 

ai/gal 40 gal 

100 

[Baseline; No-G] 

0.030 

[No-R] 3.42 10 0.00103 

0.430 

[Baseline; G] 

0.006 

[PF5] 0.0146 1,700 0.000206 

0.430 

[Baseline; G] 

0.003 

[PF10] 0.0146 1,700 0.000103 

Sprays using Backpack Sprayer 

0.059 lb 

ai/gal 40 gal 

2.50 

[Baseline; G] 

0.030 

[No-R] 0.0858 290 0.00103 

1.6 

[DL-G] 

0.006 

[PF5] 0.0548 460 0.000206 
Page 19 of 22 

Table 6.1a. Occupational Handler Exposure and Risk Estimates for Pirimiphos-methyl. Exposure Scenario and Product 

Target Site 

Application Ratea

Amount Handled 

Dermal Unit Exposureb(mg/lb) [Mitigation Level]

Inhalation Unit Exposureb(mg/lb) [Mitigation Level] 

Dermal Dosec (mg/kg/day) 

Dermal MOEdLOC = 1,000 

Inhalation Dosee (mg/kg/day) 

InhMOLO3,0

1.6 

[DL-G] 

0.003 

[PF10] 0.0548 460 0.000103 

a. Maximum single application rates are based on registered labels (see Table 4.0). b. Occupational Pesticide Handler Unit Exposure Surrogate Reference Table (March, 2014). Baseline clothing or single layer (SL): long-sleeved shirt, long pants, shoes 

chemical-resistant gloves. DL: double layer clothing which includes coveralls or apron plus baseline clothing. No-R: no respirator. PF5 or PF 10 respirator. 

c. Dermal Dose (mg/kg/day) = [Dermal Unit Exposure (mg/lb ai) * Application Rate * Amount Handled]/Body Weight (69 kg). 

d. Dermal MOE = NOAEL (25 mg/kg/day)/Dermal Dose (mg/kg/day); LOC= 1,000. e. Inhalation Dose (mg/kg/day) = [Inhalation Unit Exposure (mg/lb ai) * Application Rate * Amount Handled]/Body Weight (69 kg).

f. Inhalation MOE = NOAEL (0.73 mg/kg/day)/Inhalation Dose (mg/kg/day); LOC = 3,000. g. ARI = Aggregate Risk Index = 1÷ [(Dermal LOC ÷ Dermal MOE) + (Inhalation LOC ÷ Inhalation MOE)]. ARI≥1 not of concern. 
Page 20 of 22 

Table 6.1b. Occupational Non-Cancer Primary & Secondary Handlers Exposure and Risk Estimates for Seed-Treatment for Pirimiphos-metExposure Scenario 

Seed Species 

Mitigation Level 

Dermal Unit Exposure (mg/lb ai)a

Inhalation Unit Exposure (mg/lb ai)a

Application Rate (lb ai/lb seed) 

Amount Handledb(lb seed treated/day) 

Dermal Dosec(mg/kg/day) 

Dermal MOEd

Primary Handlers 

Loader/Applicator 

Loading/Applying Liquid for Seed Treatment 

Corn Single 

Layer, Gloves 

0.023 0.00034 0.000008 339,500 0.00091 28,000 

Sorghum 360,000 0.00096 26,000 

Sewer 

Sewing Seeds after Seed treatment 

Corn Single 

Layer, No Gloves 

0.0062 0.00023 0.000008 339,500 0.00024 100,000 

Sorghum 360,000 0.00026 97,000 

Bagger 

Bagging Seeds after Seed treatment 

Corn Single 

Layer, No Gloves 

0.0091 0.00016 0.000008 339,500 0.00036 70,000 

Sorghum 360,000 0.00038 66,000 

Multiple Activities Worker 

Multiple Activities for Seed treatment 

Corn Single 

Layer, Gloves 

0.042 0.0016 0.000008 339,500 0.00165 15,000 

Sorghum 360,000 0.00175 14,000 

Secondary Handlers 

Planters 

Secondary Seed Handlers: planting seeds in the field 

Corn Single 

Layer, Gloves 

0.25 0.0034 0.000008 6,000 0.0001714 150,000 

Sorghum 1,800 0.0000527 470,000 

a. Unit Exposures from HED Exposure Science Advisory Council Policy 14: Standard Operating Procedures for Seed Treatment (baseline inhalation = no respirator). b. HED default for lb seed treated/planted per day from HED Exposure Science Advisory Council Interim Policy 15.1 and the BEAD memo “Acres Planted Per Day and 

in the United States” (J. Becker, March 2011). 

c. Daily Dermal Dose (mg/kg/day) = Unit Exposure (mg/lb ai) * Application Rate (lb ai/lb seed) * Daily Amount Handled/Body Weight (69 kg). d. Dermal MOE = NOAEL (25 mg/kg/day)/Dermal Dose (mg/kg/day); LOC= 1,000. e. Daily Inhalation Dose (mg/kg/day) = Unit Exposure (mg/lb ai) * Application Rate (lb ai/lb seed) * Daily Amount Handled/Body Weight (69 kg). f. Inhalation MOE = NOAEL (0.73 mg/kg/day)/Inhalation Dose (mg/kg/day); LOC = 3,000. 

g. ARI = Aggregate Risk Index = 1÷ [(Dermal LOC ÷ Dermal MOE) + (Inhalation LOC ÷ Inhalation MOE)]. ARI≥1 not of concern. 
Page 21 of 22 

6.2 Occupational Post-application Exposure/Risk Estimates 

HED uses the term post-application to describe exposures that occur when individuals are 

present in an environment that has been previously treated with a pesticide (also referred to as reentry exposure). Such exposures may occur when workers enter previously treated areas to 

perform job functions, including activities related to crop production, such as scouting for pests 

or harvesting. Post-application exposure levels vary over time and depend on such things as the 

type of activity, the nature of the crop or target that was treated, the type of pesticide application, 

and the chemical’s degradation properties. In addition, the timing of pesticide applications, 

relative to harvest activities, can greatly reduce the potential for post-application exposure. 

6.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates 

There are multiple potential sources of post-application inhalation exposure to individuals 

performing post-application activities in previously treated fields. These potential sources 

include volatilization of pesticides and resuspension of dusts and/or particulates that contain 

pesticides. The Agency sought expert advice and input on issues related to volatilization of 

pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel 

(SAP) in December 2009, and received the SAP’s final report on March 2, 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The Agency has 

evaluated the SAP report and has developed a Volatilization Screening Tool and a subsequent 

Volatilization Screening Analysis (http://www.regulations.gov/#!docketDetail;D=EPA-HQOPP-2014-0219). During Registration Review, the agency will utilize this analysis to determine 

if data (i.e., flux studies) or further analysis is required for pirimiphos-methyl. 

A post-application inhalation exposure assessment is not required as exposure is expected to be 

negligible. Seed treatment assessments provide quantitative inhalation exposure assessments for 

primary (i.e., seed treaters) and secondary handlers (i.e., planters). It is expected that these 

exposure estimates would be protective of any potential low-level post-application inhalation 

exposure that could result from these types of applications. 

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates 

A quantitative post-application dermal exposure assessment was not conducted since such 

exposure is also expected to be negligible. Post-application exposure from treated stored 

grain/seeds is unlikely because sustained levels of contact with treated stored grain/seed after 

application is not expected. Commercial applicators rarely have direct contact with the stored 

grain during testing of grain, maintenance, or other intermittent activities. In addition, a postapplication dermal exposure is not expected for workers distributing and/or removing ear-tags 

from treated animals (cattle). Therefore, a quantitative post-application dermal assessment was 

not conducted. 

No REI is listed on the registered product labels, as the label-defined use sites are not subject to 

the Worker Protection Standard (WPS). 
Page 22 of 22 

Appendix A. Summary of Occupational Non-cancer Algorithms 

Occupational Non-cancer Handler Algorithms 

Potential daily exposures for occupational handlers are calculated using the following formulas: 

E=UE * AR * A * 0.001 mg/ug

where: 

E = exposure (mg ai/day), 

UE = unit exposure (μg ai/lb ai), 

AR = maximum application rate according to label (lb ai A or lb ai/gal), and 

A = area treated or amount handled (e.g., A/day, gal/day). 

 

The daily doses are calculated using the following formula: 

ADD= 

E * AF

BW

where: 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day), 

E = exposure (mg ai/day), 

AF = absorption factor (dermal and/or inhalation), and 

BW = body weight (kg). 

Margin of Exposure: Non-cancer risk estimates for each application handler scenario are 

calculated using a Margin of Exposure (MOE), which is a ratio of the toxicological endpoint to 

the daily dose of concern. The daily dermal and inhalation dose received by occupational 

handlers are compared to the appropriate POD (i.e., NOAEL) to assess the risk to occupational 

handlers for each exposure route. All MOE values are calculated using the following formula: 

MOE= 

POD

ADD

where: 

MOE = margin of exposure: value used by HED to represent risk estimates (unitless), 

POD = point of departure (mg/kg/day), and 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day).