UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

Date: 

Subject: 

August 4, 2015 

Triclopyr. Occupational and Residential Exposure Assessment for a 

Reevaluation of Existing Residential Uses with the Updated Residential 

Standard Operation Procedures (SOPs). 

PC Code: I 16000, I 16001 , 116002, 1 16004 

Decision No.: 488478 

DP Barcode: 0426070 

Registration No.: 62719-37, 627 19-53, 62719-87, 

627 I 9-552, 627 I 9-637, 627 I 9-AIT(687) 

Petition No.: 4F8249, 4F8279 Regulatory Action: Section 3 

Risk Assessment Type: Case No.: 2710 

Occupational/Residential Exposure Assessment 

TXRNo.: NA CAS No.: 55335-06-3, 572 13-69-1, 64700-56-7,/ 

FROM: Lata Venkateshwara, Environmental Scientist 

1048373-85-8 w~ 

40CFR: §180.417 \)tr\.. 

l-rMRID No.: NA 

Jennifer R. Tyler, Chemist ~ ~~J /....,_ _____ ___ 

Risk Assessment Branch 1 (RAB I) ~ ~ 

Health Effects Division (HED; 7509P) 

THROUGH: 

Charles 

Kelly M. 

Smith, 

Lowe, 

Branch 

Environmental 

Chief Cf'" Scientist ~ 

-~ 

~ 

~ 

RAB1/HED(7509P) ~ 

TO: 

Introduction 

Mindy Ondish, Risk Reviewer 

Reuben Baris, Product Manager 25 

Herbicide Branch (HB) 

Registration Division (RD, 7505P) 

RD forwarded an action to HED for triclopyr that included: 1) the removal of a grazing 

restriction for lactating dairy cattle, and the establishment of milk and milk fat tolerances; 

and 2) the registration of triclopyr choline salt for use on all existing registered uses. Neither 

of these actions is anticipated to require a quantitative occupational exposure assessment 

since no new uses are being requested. The rates for triclopyr choline salt on existing 

registered uses are no higher than what was assessed previously, so no new assessments are 

required. No new residential uses are being requested either; however, since _a revised 

dietary assessment is required to incorporate the new tolerances, a reevaluation of existing 

Page 1 of 17 
Page 2 of 17

triclopyr residential uses has been performed for inclusion in an updated aggregate 

assessment. The reevaluation reflects updates to HED’s 2012 Residential Standard 

Operating Procedures (SOPs) along with policy changes for body weight assumptions.

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 the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the 

Agricultural Handler Exposure Task Force (AHETF) database; the Outdoor Residential 

Exposure Task Force (ORETF) database; and the Residential SOPs (Lawns/Turf). Some of

these data are proprietary, and subject to the data protection provisions of the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA). 

 
Page 3 of 17

Table of Contents

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

2.0 Risk Assessment Conclusions and Recommendations.................................................. 6

2.1 Summary of Risk Estimates....................................................................................... 6

2.2 Label Recommendations from Occupational/ Residential Assessment..................... 6

2.3 Data Deficiencies and Requirements ......................................................................... 6

3.0 Hazard Characterization................................................................................................. 6

4.0 Proposed Use Profile...................................................................................................... 9

5.0 Residential Exposure and Risk Estimates...................................................................... 9

5.1 Residential Handler Exposure/Risk Estimates......................................................... 10

5.2 Residential Post-application Exposure/Risk Estimates............................................ 11

5.3 Residential Risk Estimates for Use in Aggregate Assessments............................... 12

5.4 Spray Drift ............................................................................................................ 14

5.5 Residential Bystander Post-Application Inhalation Exposure.............................. 14

6.0 Occupational Exposure and Risk Estimates ................................................................ 14
Page 4 of 17

1.0 Executive Summary

This document presents a reevaluation of existing triclopyr residential uses to support a 

submitted action that includes: 1) the removal of a grazing restriction for lactating dairy cattle 

and the establishment of milk and milk fat tolerances; and 2) the registration of triclopyr 

choline salt for use on all existing registered uses. Neither of these actions is anticipated to 

require a quantitative occupational exposure assessment since no new uses are being 

requested. The rates for triclopyr choline salt on existing registered uses are no higher than 

what was assessed previously, so no new assessments are required.

The proposed actions will not result in new residential exposures; however, the currently 

registered turf and aquatic use have been reassessed in this document to reflect updates to 

HED’s 2012 Residential SOPs along with policy changes for body weight assumptions. The 

residential exposures have been revised since they will impact the aggregate assessment for 

triclopyr.

Use Profile: Triclopyr, triclopyr TEA, and triclopyr BEE products are used as selective 

herbicides to control broadleaf weeds and woody brush. Triclopyr products are registered for 

use on rice as well as a variety of terrestrial non-agricultural sites (rights of way, pasture and 

rangelands, forests, and turf including home lawns, golf courses, and athletic fields) and 

aquatic sites (lakes, ponds, reservoirs, and wetlands). Triclopyr products are formulated as 

soluble concentrates, emulsifiable concentrates, liquids (pressurized and ready-to-use), 

granules, wettable powders, and pellets. 

Exposure Profile: While occupational exposures are anticipated from the proposed triclopyr 

choline salt uses, a quantitative assessment has not been conducted since the rates for these 

uses are not higher than what has already been assessed.

The registered residential uses (turf and aquatic use) result in handler inhalation and postapplication inhalation and ingestion exposures for adults, post-application inhalation and 

ingestion exposure for children (3 to <6 years old), and post-application incidental oral 

exposures for children (1 to <2 years old). The dermal route of exposure is not quantitatively 

assessed because there is no dermal hazard. Short-term exposures are anticipated for 

residential handlers, while short- and intermediate-term residential post-application 

exposures are expected. Chronic exposures are not anticipated.

Hazard Characterization: A short-term dermal endpoint was not selected since there were no 

adverse dermal or systemic effects observed in a 28-day dermal study in rats. Dermal 

endpoints were previously selected for the intermediate- and long-term scenarios for 

triclopyr; however, a reevaluation of the available data indicates that the toxicity profile for 

triclopyr does not show progression of toxicity with increased duration. HED identified 

short- and intermediate-term inhalation and incidental oral toxicological points of departure

(PODs). The no-observed adverse-effect level (NOAEL) for short- and intermediate-term 

inhalation and incidental oral exposure is 5 mg/kg/day. Triclopyr is classified as “not likely 

to be carcinogenic to humans.” HED’s level of concern (LOC) for non-cancer risks (i.e., 

LOC for Margins of Exposure (MOEs)) is defined by uncertainty factors. HED applies a 
Page 5 of 17

10X factor to account for inter-species extrapolation and a 10X factor to account for intraspecies variation. The subchronic inhalation study is required at this time, and an additional 

10X database uncertainty factor will be applied for assessment of inhalation exposure 

scenarios. The total uncertainty factor that is applied to inhalation risk assessments is 1000X

for short- and intermediate-term risks, while the factor applied to incidental oral risk 

assessments is 100x for short- and intermediate-term risks. 

Residential Exposure and Risk Estimates: The results of the residential handler exposure and 

risk assessment indicate that short-term inhalation risks are not of concern (i.e. MOEs ≥1000) 

for all turf scenarios. Short-term incidental oral post-application risk estimates for all turf 

scenarios are not of concern to HED (i.e., MOEs ≥ 100). Short-term incidental oral postapplication risk estimates are protective of intermediate-term because the POD is the same. 

Short-term inhalation post-application risk estimates for all swimmer scenarios are not of 

concern to HED (i.e., MOEs ≥ 1000). Furthermore, short-term inhalation post-application 

risk estimates are protective of intermediate-term because the POD is the same. The postapplication ingestion risk estimates for swimmers are also not of concern to HED (i.e., MOEs 

≥ 100).

Occupational Exposure and Risk Estimates: The proposed action to remove a grazing 

restriction for dairy cattle is not expected to result in occupational exposures; and the 

proposed registration of the choline salt is covered by the previous actions. As a result, no 

new occupational assessments have been conducted for these actions. However, 

occupational handler inhalation exposure and risk estimates were updated to reflect all of the 

currently registered uses of triclopyr for the July 2014 HASPOC meeting in order to assess 

the inhalation waiver request submitted by the triclopyr registrants. Besides mixer/loader for 

aerial applications to forestry, all occupational inhalation MOEs are 1,200-180,000. For 

mixers/loaders of the liquid formulation for aerial application by helicopter to forestry, the 

inhalation MOE is 41 (see Table 6.1).

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 Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the 

Agricultural Handler Exposure Task Force (AHETF) database; the Outdoor Residential 

Exposure Task Force (ORETF) database; and the Residential SOPs (Lawns/Turf; Aquatic 

Use), 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 http://www.epa.gov/pesticides/science/handler-exposure-data.html and 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 6 of 17

2.0 Risk Assessment Conclusions and Recommendations

2.1 Summary of Risk Estimates

Occupational Exposure and Risk Estimates: The proposed action to remove a grazing 

restriction for dairy cattle is not expected to result in occupational exposures; and the 

proposed registration of the choline salt is covered by the previous actions. No new 

occupational assessments have been conducted. 

Residential Exposure and Risk Estimates: There are no risk estimates of concern for all 

registered residential uses of triclopyr.

2.2 Label Recommendations from Occupational/ Residential Assessment 

No label recommendations are required at this time.

2.3 Data Deficiencies and Requirements

There are no data deficiencies or data requirements for the proposed new use of triclopyr.

3.0 Hazard Characterization

Acute Toxicity: The acute toxicity categories are presented in Tables 3.1 -3.3.

Table 3.1. Acute Toxicity Profile – Triclopyr Acid.

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral 00031940 LD50 = 729 mg/kg (M)

LD50 = 630 mg/kg (F) III

870.1200 Acute dermal 00056009 LD50 > 2000 mg/kg III

Table 3.2. Acute Toxicity Profile – Triclopyr Triethylamine Salt.

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral 41443301 LD50 = 1847 mg/kg III

870.1200 Acute dermal 41443302 LD50 > 2000 mg/kg III

870.1300 Acute inhalation 41443303 LC50 > 2.6 mg/L III

870.2400 Primary eye irritation 41443304 corrosive I 

870.2500 Primary skin irritation 41443305 not irritating IV

870.2600 Dermal sensitization 41443306 sensitizer --
Page 7 of 17

Table 3.3. Acute Toxicity Profile – Triclopyr Butoxyethyl Ester.

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral 40557004 LD50 = 803 mg/kg III

870.1200 Acute dermal 40557005 LD50 > 2000 mg/kg III

870.1300 Acute inhalation 40557006 LC50 > 4.8 mg/L III

870.2400 Primary eye irritation 40557007 minimally irritating III

870.2500 Primary skin irritation 40557008 not irritating IV

870.2600 Dermal sensitization 40557009 sensitizer --

Toxicological PODs Used for Risk Assessment: The bioequivalency of the three chemical 

forms of triclopyr (acid, triethylamine salt, and butoxyethyl ester) has been addressed 

through a variety of special studies with the salt and ester forms, including data on 

comparative disposition, plasma half-life, tissue distribution, and hydrolytic cleavage. These 

studies were found to adequately address the issue of bioequivalency. In addition, in a memo 

dated 22-MAR-2012, HED reviewed a request to determine the bioequivalence between 

triclopyr and triclopyr choline salt, and agreed that bioequivalence was supported by the 

currently available information (Memo, G. Kramer, D399410). Therefore, studies conducted 

with any one form of triclopyr have been used to support the toxicology database as a whole. 

Triclopyr has been classified as having low acute toxicity via the oral, dermal and inhalation 

routes (Toxicity Category III-IV). The salt form was found to be corrosive to the eye, while 

the ester form was only minimally irritating. Both the salt and ester forms of triclopyr were 

found to be dermal sensitizers, but not a dermal irritant.

Waivers have been submitted by the registrant for the acute neurotoxicity (ACN) and 

subchronic inhalation studies. The HED Hazard and Science Policy Council (HASPOC) 

discussed the need for these studies using a WOE approach (J. Leshin; TXR# 0057009). 

HASPOC concluded that the ACN is not required at this time. The subchronic inhalation 

study is required at this time, and an additional 10X database uncertainty factor will be 

applied for assessment of inhalation exposure scenarios. 

The toxicity endpoints and the PODs for various exposure scenarios are presented in Tables

3.4 and 3.5.

Table 3.4. Summary of Toxicological Doses and Endpoints for Triclopyr for Use in Dietary and NonOccupational Human Health Risk Assessments.

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/F

QPA Safety 

Factors

RfD, PAD, Level 

of Concern for 

Risk Assessment

Study and Toxicological Effects

Acute Dietary

(General 

Population 

including infants 

and children)

NOAEL = 100 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA = 1X

aRfD = 1.0 

mg/kg/day

aPAD = 1.0 

mg/kg/day

Developmental Rat Toxicity Study 

with ester

Maternal LOAEL = 300 mg/kg/day 

based on mortality (other effects seen 

at this dose included clinical signs, 

necropsy findings, decreased food and 

water consumption, and increased 

kidney and liver weights).
Page 8 of 17

Table 3.4. Summary of Toxicological Doses and Endpoints for Triclopyr for Use in Dietary and NonOccupational Human Health Risk Assessments.

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/F

QPA Safety 

Factors

RfD, PAD, Level 

of Concern for 

Risk Assessment

Study and Toxicological Effects

Acute Dietary

(Females 13-50 

years old)

NOAEL = 5 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA = 1X

aRfD = 0.05 

mg/kg/day

aPAD = 0.05 

mg/kg/day

Two-Generation Rat Reproduction 

Study with acid

LOAEL = 25 mg/kg/day based on 

increased incidence of rare 

malformations (exencephaly and 

ablepharia)

Chronic Dietary

(All Populations)

NOAEL = 5 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA = 1X

cRfD = 0.05 

mg/kg/day

cPAD = 0.05 

mg/kg/day

Two-Generation Rat Reproduction 

Study with acid

LOAEL = 25 mg/kg/day based on 

degeneration of the proximal renal 

tubules 

Incidental Oral 

Short-Term (1-30 

days) and 

IntermediateTerm (1-6 

months) 

NOAEL = 5 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA = 1X

Residential LOC 

for MOE = 100

Subchronic Oral Rat Toxicity Study 

with acid

LOAEL = 20 mg/kg/day based on 

degeneration of the proximal renal 

tubules

Dermal

Short-Term (1-30 

days) and 

IntermediateTerm (1-6 

months) 

No hazard was identified for dermal exposure; therefore a quantitative dermal assessment is not 

needed.

Inhalation

Short-Term (1-30 

days) and 

IntermediateTerm (1-6 

months)

NOAEL = 5 

mg/kg/day

Inhalation 

assumed 

equivalent to 

oral

UFA = 10X

UFH = 10X

FQPA = 10X

Residential LOC 

for MOE = 1000

Subchronic Oral Rat Toxicity Study 

with acid

LOAEL = 20 mg/kg/day based on 

degeneration of the proximal renal 

tubules

Cancer (oral, 

dermal, 

inhalation)

Classified as a “Group D Chemical – unable to be classified as to human carcinogenicity”

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). UFL = use of a LOAEL to 

extrapolate a NOAEL. FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = reference dose. 

MOE = margin of exposure. LOC = level of concern. 
Page 9 of 17

Table 3.5. Summary of Toxicological Doses and Endpoints for Triclopyr for Use in Occupational Human 

Health Risk Assessments

Exposure/ 

Scenario

Point of 

Departure

Uncertainty 

Factors

Level of Concern 

for Risk 

Assessment

Study and Toxicological 

Effects

Dermal

Short-Term (1-30 

days) and 

IntermediateTerm (1-6 

months) 

No hazard was identified for dermal exposure; therefore a quantitative dermal assessment is not 

needed.

Inhalation

Short-Term (1-30 

days) and 

IntermediateTerm (1-6 

months)

NOAEL = 5 

mg/kg/day

Inhalation 

assumed 

equivalent to oral

UFA = 10X

UFH = 10X

UFDB = 10X

Occupational LOC 

for MOE = 1000

Subchronic Oral Rat Toxicity 

Study with acid

LOAEL = 20 mg/kg/day based 

on degeneration of the 

proximal renal tubules

Cancer (oral, 

dermal, 

inhalation)

Classified as a “Group D Chemical – unable to be classified as to human carcinogenicity”

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). UFL = use of a LOAEL to 

extrapolate a NOAEL. MOE = margin of exposure. LOC = level of concern. 

Body Weight: The standard body weight for the general population (80 kg) was used for all 

exposure scenarios covered in this risk assessment since the endpoints selected were not 

developmental and/or fetal effects.

4.0 Proposed Use Profile

The current actions for triclopyr include the 1) removal of a grazing restriction for lactating 

dairy cattle and the establishment of milk and milk fat tolerances; and 2) the registration of 

triclopyr choline salt for use on all existing registered uses. Neither of these actions is 

anticipated to require a quantitative occupational exposure assessment since no new uses are 

being requested. No new residential uses are being requested either; however, since a revised 

dietary assessment is required to incorporate the new tolerances, a reevaluation of existing 

triclopyr residential uses has been performed for inclusion in an updated aggregate 

assessment. The reevaluation reflects updates to HED’s 2012 Residential SOPs along with 

policy changes for body weight assumptions.

5.0 Residential Exposure and Risk Estimates

The proposed uses do not involve applications by homeowners or commercial applicators in 

residential settings. Therefore, no new residential exposure is expected. However, there are 

existing residential uses that have been reassessed in this document to reflect updates to 

HED’s 2012 Residential SOPs (http://www.epa.gov/pesticides/science/residential-exposuresop.html) along with policy changes for body weight assumptions. The revision of 

residential exposure estimates will impact the human health aggregate risk assessment for 

triclopyr.
Page 10 of 17

Triclopyr is registered for use on several terrestrial non-agricultural use sites including rightsof-way, pasture and rangelands, forests, and turf, including home lawns golf courses and 

athletic field. The residential lawn uses include spot and broadcast applications. It is also 

used in aquatic settings to control aquatic weeds growing in lakes, ponds, reservoirs, and 

wetlands, and to control woody brush and herbaceous weeds in wetlands and on the banks 

and shores of aquatic sites. 

According to the most recent scoping document, there are hundreds of products that contain 

triclopyr, triclopyr salts, and triclopyr esters. HED focused on a subset of these labels that 

covered a majority of the uses in order to identify relevant use sites and application rates for 

this reassessment. Table 5.0.1 below summarizes the scenarios and rates assessed.

Table 5.0.1. Summary of Relevant Residential Use Patterns for Reevaluation

Chemical 

Name

Registration 

Number and 

Product Name

Use Site

Formulation 

and Percent 

Active 

Ingredient

Application 

method Maximum App Rate

Triclopyr 

triethylamine 

salt (116002) 

62719-226 Dow 

AgroSciences 

Brush & Weed 

Herbicide

For the control of 

woody plants, vines 

and broadleaf weeds 

around homes, cabins, 

fences, walkways and 

other non-crop areas. 

Contains Hammer 

Herbicide. This 

product is for outdoor 

residential use only.

Soluble 

Liquid (SL) 

8.8%

Ground, hose end 

sprayer, tank type 

sprayer, backpack 

sprayer

9 lb ae/A

0.0375

lb ae/gal

0.0096 lb ae/ ft2

Triclopyr, 

butoxyethyl 

ester 

(116004)

62719-566 Turflon 

Ester Ultra

Golf course turf, 

ornamental lawn and 

turf 

EC 60.5% Ground (sprayer) 1.5 lb ae /A

Triclopyr 

triethylamine 

salt (116002)

62719-187 

Renovate* Aquatic areas/water SL 44.4 %

Spray boom, 

handgun, or other 

suitable 

equipment 

mounted on a 

boat or vehicle, 

helicopter.

6 lb ae/A

(equivalent to 0.552 

mg/L water 

concentration)

Residential handler assessments were only conducted for the turf uses, and not the aquatic 

use sites because the aquatic sites are not residential in nature and homeowner applications 

are unlikely. It is noted that the aquatic label includes the following statements which imply 

commercial/professional applications: (1) state and/or local authorities are to be consulted 

prior to applying this product to public waters; and (2) State or local public agencies may 

require permits.

5.1 Residential Handler Exposure/Risk Estimates

Summary of Residential Handler Non-Cancer Exposure and Risk Estimates

Residential handler assessments were only conducted for the turf uses, and not the aquatic 

use sites because the aquatic sites are not residential in nature and homeowner applications 
Page 11 of 17

are unlikely. It is noted that the aquatic label includes the following statements which imply 

commercial/professional applications: (1) state and/or local authorities are to be consulted 

prior to applying this product to public waters; and (2) State or local public agencies may 

require permits. Table 5.0.2 presents the residential handler exposures and risks for triclopyr, 

triclopyr TEA and triclopyr BEE.

Table 5.0.2. Residential Handler Exposure and Risk for Triclopyr, Triclopyr TEA, and Triclopyr BEE.

Exposure Scenario Application 

Rate a

Amount 

Handledb

Unit 

Exposure

(mg/lb ai)b

Dose 

(mg/kg/day)d

MOEe

(LOC = 

1000)

Baseline 

Inhalationc

Baseline 

Inhalation

Baseline 

Inhalation

Mixing/Loading/Applicator – Turf

Mixing/Loading/Applying Liquids with 

Hose End Sprayer 9 lb ae/acre 0.5 acres 0.022 0.0012 4,000

Mixing/Loading/Applying Liquids with 

Manually Pressurized Handwand

0.0375

lb ae/gal 5 gallons 0.018 0.000042 120,000

Mixing/Loading/Applying Liquids with 

Sprinkler Can

0.0096 lb 

ae/ ft2

1000

ft2 0.022 0.0026 1,900

Mixing/Loading/Applying Liquids with 

Backpack

0.0375

lb ae/gal 5 gallons 0.14 0.00033 15,000

a. Application rate based on label Dow AgroSciences Brush &Weed Herbicide (Reg. No. 62719-226).

b. Unit exposure values and estimates for area treated or amount handled based on Exposure Science Advisory Council 2012 

Residential SOPs: http://www.epa.gov/pesticides/science/residential-exposure-sop.html

c. Baseline Inhalation: no respirator.

d. Inhalation Dose (mg/kg/day) = daily unit exposure (mg/lb ae) * application rate (lb ae/unit volume or area) * amount handled 

(unit volume or area) * inhalation absorption (100%) / body weight (80 kg). 

e. MOE = NOAEL (short- term inhalation = 5 mg/kg/day) / daily dose (mg/kg/day). LOC = 1000.

5.2 Residential Post-application Exposure/Risk Estimates

Summary of Residential Post-Application Non-Cancer Exposure and Risk Estimates

Table 5.0.3 presents the post-application incidental oral MOE values calculated for the 

broadcast liquid application of triclopyr, triclopyr TEA, and triclopyr BEE to turf. The postapplication MOEs for hand-to-mouth, object to mouth and soil ingestion are not of concern 

to HED (MOEs range from 220 to 98,000). 

Table 5.0.3. Residential Post-application Non-cancer Exposure and Risk Estimates for Triclopyr, Triclopyr TEA, and 

Triclopyr BEE.

Lifestage

Post-application Exposure Scenario Application 

Ratea

Dose 

(mg/kg/day)b

MOEsc

Use Site Route of Exposure (LOC = 100)

Child

(1 to <2 years old)

Liquid Application to 

Turf

ST Hand-to-Mouth

1.5 lb ae/acre

0.0228 220

ST Object-to-mouth 0.00069 7,200

ST/IT Soil Ingestion 5.1E-04 98,000

a Based on label Dow AgroSciences Turflon Amine (Reg. No. 62719-257). 

b Dose (mg/kg/day) equations (see Appendix B)

c MOE = NOAEL ÷ Daily Dose (mg/kg/day). ST/IT Incidental Oral and Inhalation NOAEL = 5 mg/kg/day. Level of concern = 100.

Tables 5.0.4 and 5.0.5 provide the post-application inhalation and ingestion risk estimates for 

exposure of swimmers to triclopyr. 
Page 12 of 17

Table 5.0.4. Short -Term Post-application Exposure - Inhalation of Water by Swimmers.

Exposure Scenario Cw1 (mg/L) IR2 (L/hr) ET3

(hr/day) BW4 (kg) Exposure5 Absorbed Dose6(mg/kg/day)

MOE7

(LOC = 

1000)

Swimmer; adult 0.552 0.64 0.025 80 9.1E-05 1.14E-06 4,400,000

Swimmer; child (3 to <6 years old) 0.42 0.076 19 1.8E-04 9.55E-06 520,000 1 Cw = concentration in water is based on the application rate provided on the product label. An assumption of 4 feet depth 

(and uniform distribution) was used to estimate the concentration in water. 2 IR = inhalation of water; based on the Risk Assessment Guidance for Superfund (RAGS) Part A 

(http://www.epa.gov/oswer/riskassessment/ragsa/) which references a value from the Superfund Exposure Assessment 

Manual (USEPA, 1988). The recommended point estimate for use in post-application incidental ingestion exposure 

assessments is 0.05 L/hr of swimming for adults and children 3 to <6 years old. 3 ET =exposure time; based on 2011 Exposure Factors Handbook (Table 16-20). 4 BW = body weight; based on the Residential Pesticide Exposure Assessment SOP (February-2012). 5 Exposure = (VVpp* IR * ET ) 6 Absorbed Inhalation dose = (E x AF) ÷ BW 7 MOE = NOAEL (5 mg/kg/day; adult and child) ÷ dose (mg/kg/day)

Table 5.0.5. Short -Term Post-application Exposure - Ingestion of Water by Swimmers.

Exposure Scenario Cw1

(mg/L) IgR2 (L/hr) ET3 (hr/day) BW4 (kg) Oral Dose5 (mg/kg/day) MOE6(LOC = 100)

Swimmer; adult 0.552 0.05 0.025 80 0.000008625 580,000

Swimmer; child (3 to <6 years old) 0.05 0.076 19 0.0001104 45,000 1 Cw = concentration in water is based on the application rate provided on the product label. An assumption of 4 feet depth 

(and uniform distribution) was used to estimate the concentration in water. 2 IgR = ingestion rate of water; based on the Risk Assessment Guidance for Superfund (RAGS) Part A 

(http://www.epa.gov/oswer/riskassessment/ragsa/) which references a value from the Superfund Exposure Assessment 

Manual (USEPA, 1988). The recommended point estimate for use in post-application incidental ingestion exposure 

assessments is 0.05 L/hr of swimming for adults and children 3 to <6 years old. 3 ET =exposure time; based on 2011 Exposure Factors Handbook (Table 16-20). 4 BW = body weight; based on the Residential Pesticide Exposure Assessment SOP (February-2012). 5 Oral dose = (Cw x IgR x ET) ÷ BW 6 MOE = NOAEL (5 mg/kg/day; adult and child) ÷ dose (mg/kg/day)

5.3 Residential Risk Estimates for Use in Aggregate Assessments

Tables 5.3.1 and 5.3.2 reflects the residential risk estimates that are recommended for use in 

the aggregate assessment for triclopyr.

MOE Approach (Table 5.3.1)

• The recommended residential exposure for use in the short-term aggregate assessment 

for children 1 to <2 years old reflects hand-to-mouth incidental oral exposure due to 

applications to turf.

Aggregate Risk Index (ARI) Approach (Table 5.3.2)

• The recommended residential exposures for use in the short-term aggregate 

assessment for adults reflects handler inhalation exposures from spot applications to 

turf via sprinkler can.

• The recommended residential exposure for use in the short-term aggregate assessment 

for children 3 to <6 years old reflects combined inhalation and ingestion of water by 

swimmers.
Page 13 of 17

Table 5.3.1. Recommendations for the Residential Exposures for the Triclopyr Aggregate Assessment Using Total MOE Approach.

1

Lifestage

Residential Handler Residential Post-application

Dose (mg/kg/day)2 MOE3 Dose (mg/kg/day)4 MOE5

Dermal Inhalation Total Dermal Inhalation Total Dermal Inhalation Oral Total Dermal Inhalation Oral Total

Child (1 to <2 

years old) –

ST Hand-toMouth 

Exposure Due 

to Turf Use

N/A - - 0.0228 - - - 220 220

1. Bolded risk estimates should contribute to the residential exposure portion of the aggregate assessment. 

2. Residential Handler Dose = the highest handler doses for each applicable lifestage of all scenarios assessed. Not applicable.

3. Residential Handler MOE = the MOEs associated with the highest doses identified. Not applicable.

4. Residential Post-application Dose = the highest post-application dose for each applicable lifestage of all scenarios assessed (see Tables 5.0.3 through 5.0.5). Total = incidental oral.

5. Residential Post-application MOE = the MOEs associated with the highest doses identified (see Tables 5.0..3 through 5.0.5). Total MOE = 1/[(1/Inhalation MOE) + (1/Incidental oral MOE)], 

where applicable. 

Table 5.3.2. Recommendations for the Residential Exposures for the Triclopyr Aggregate Assessment Using ARI Approach.

1

Lifestage

Residential Handler Residential Post-application

Dermal

MOE

Dermal 

ARI

Inhalation 

MOE2

Inhalation

ARI2

Dermal 

MOE

Dermal

ARI

Inhalation 

MOE2

Inhalation 

ARI2

Oral 

MOE3

Oral 

ARI3

Total 

ARI4

Adult – M/L/A Liquids to 

Turf with Sprinkler Can - - 1,900 1.9 N/A

Child (3 to <6 years old) –

Swimmer Exposure Due to 

Aquatic Use

N/A - - 520,000 520 45,000 450 240

1. Bolded risk estimates should contribute to the residential exposure portion of the aggregate assessment.

2. MOE inhalation residential exposure = [(short-term inhalation NOAEL)/(high end inhalation residential exposure)]. ARI inhalation = [(MOE inhalation residential exposure)/(MOE target)]. 

Short-term inhalation NOAEL = 5 mg/kg/day; high-end inhalation residential handler exposure for adults = 0.0026 mg/kg/day; high-end inhalation residential post-application exposure for 

children 3 to <6 years old = 0.00000955 mg/kg/day (swimmer). MOE target = 1000.

3. MOE oral residential exposure = [(short-term oral NOAEL)/(high-end incidental oral residential exposure)]. ARI oral residential exposure = [(MOE oral residential exposure)/(MOE target)]. 

Short-term oral NOAEL = 5 mg/kg/day; high-end incidental oral residential exposure for children 3 to <6 years old (swimmer) = 0.00001104 mg/kg/day. MOE target = 100.

4. Total ARI = 1/[(1/ARI oral) + (1/ARI inhalation)].
Page 14 of 17

5.4 Spray Drift

Spray drift is a potential source of exposure to those nearby pesticide applications. This is 

particularly the case with aerial application, but, to a lesser extent, spray drift can also be a 

potential source of exposure from the ground application methods (e.g., groundboom and airblast) 

employed for triclopyr. The agency has been working with the Spray Drift Task Force (a task 

force composed of various registrants which was developed as a result of a Data Call-In issued by 

EPA), EPA Regional Offices and State Lead Agencies for pesticide regulation and other parties to 

develop the best spray drift management practices (see the agency’s Spray Drift website for more 

information). 2 The agency has also developed a policy on how to appropriately consider spray 

drift as a potential source of exposure in risk assessments for pesticides. The potential for spray 

drift will be quantitatively evaluated for each pesticide during the Registration Review process 

which ensures that all uses for that pesticide will be considered concurrently. The approach is 

outlined in the revised (2012) Standard Operating Procedures For Residential Risk Assessment 

(SOPs) - Residential Exposure Assessment Standard Operating Procedures Addenda 1: 

Consideration of Spray Drift. This document outlines the quantification of indirect nonoccupational exposure to drift. 

5.5 Residential Bystander Post-Application Inhalation Exposure

Volatilization of pesticides may be a source of post-application inhalation exposure to individuals 

nearby pesticide applications. 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-HQ-OPP-2014-0219). 

During Registration Review, the agency will utilize this analysis to determine if data (i.e., flux 

studies, route-specific inhalation toxicological studies) or further analysis is required for triclopyr.

6.0 Occupational Exposure and Risk Estimates

The proposed action to remove a grazing restriction for dairy cattle is not expected to result in 

occupational exposures; and the proposed registration of the choline salt is covered by the previous 

actions. As a result, no new occupational assessments have been conducted for these actions. 

However, occupational handler inhalation exposure and risk estimates were updated to reflect all 

of the currently registered uses of triclopyr for the July 2014 HASPOC meeting in order to assess 

the inhalation waiver request submitted by the triclopyr registrants. 

For mixers/loaders of the liquid formulation for aerial application by helicopter to forestry, the 

inhalation MOE is 41. The current label requires baseline PPE (single layer clothing with gloves). 

With the addition of a PF5 or PF10 respirator to the label, MOEs for this scenario would increase 

to 200 and 410, respectively. These estimates are considered conservative given aerial 

applications are only made by helicopter and the high acreage default of 7,500 acres would be an 

overestimate of the acreage that would be treated. Previously, data was obtained from the U.S. 

 2 Available: http://www.epa.gov/opp00001/factsheets/spraydrift.htm 
Page 15 of 17

Army Corps of Engineers, University of South Florida, and the South Florida Water Management 

District that indicated typical acreage treated with triclopyr by helicopter was 100 acres (J.T. 

Swackhammer; 22-JUL-2002; D269448). This estimate was not used for calculating MOEs for 

this evaluation because it is based on informal discussions from over a decade ago and commercial 

users were not included the estimate. More current, all-inclusive data regarding the typical acreage 

that is treated with triclopyr using aerial applications by helicopter would be needed to refine this 

exposure scenario.

A summary of the occupational handler inhalation risk estimates from these uses of triclopyr are 

presented in Table 6.1.
Page 16 of 17

Table 6.1. Triclopyr: Summary of Occupational Handler Inhalation Risks for Currently Registered Uses.

Activity

Application Equipment Crop/Target

Inhalation 

Unit 

Exposure

(μg/lb ai)1 App Rate2 Acres3 Dose4

ST and IT 

Inhalation 

MOE 

(Baseline)5

Mitigation 

Level

Mixer/Loader

Groundboom app. of 

liquid formulation

Range and pasture, forests and non-crop areas, including manufacturing and 

storage sites, rights-of-way such as electrical power lines, communication 

lines, pipelines, roadsides, railroads, fence rows, non-irrigation ditch banks, 

and around farm buildings; and applications to grazed areas, and 

establishment and maintenance of wildlife openings, and in Christmas tree

plantations and aquatic sites.

0.219

(baseline)

0.0438 (PF5)

0.0219 (PF10)

9 lb ae/A 80 0.00198 2,500

Aerial/Helicopter app. of 

liquid formulation 6 lb ae/A 7,500

0.123 41

0.0246 200 (PF5)

0.0123 410 (PF10)

Groundboom app. of 

liquid formulation Rice 

0.219

(baseline)

0.375 lb ae/A 200 0.000205 24,000

Aerial app. of liquid 

formulation 1,200 0.00123 4,100

Applicator

Applicator, 

Aerial/Helicopter

Range and pasture, forests and non-crop areas, including manufacturing and 

storage sites, rights-of-way such as electrical power lines, communication 

lines, pipelines, roadsides, railroads, fence rows, non-irrigation ditch banks, 

and around farm buildings; and applications to grazed areas, and 

establishment and maintenance of wildlife openings, and in Christmas tree

plantations and aquatic sites.

0.0049 (EC) 6 lb ae/A 7,500 0.00414 1,800 (EC)

Applicator, Open Cab 

Groundboom

0.34 

(baseline) 9 lb ae/A 200 0.00306 1,600

Applicator, Aerial

Rice 

0.0049 (EC)

0.375 lb ae/A

1,200 0.0000276 180,000 (EC)

Applicator, Open Cab 

Groundboom

0.34 

(baseline) 200 0.0000404 16,000

Mixer/Loader/Applicator

M/L/A Backpack

Range and pastures and in non-crop areas including industrial manufacturing 

and storage sites, rights-of-way such as electrical power lines, 

communications lines, pipelines, roadsides, railroads, fence rows, nonirrigation ditch banks and around farm buildings. Use on these sites may 

include application to grazed areas, as well as establishment and maintenance 

of wildlife openings.

2.58 8 lb ae/A or 

0.75 lb ae/gal

40 

gallons 0.000968 5,200
Page 17 of 17

Table 6.1. Triclopyr: Summary of Occupational Handler Inhalation Risks for Currently Registered Uses.

Activity

Application Equipment Crop/Target

Inhalation 

Unit 

Exposure

(μg/lb ai)1 App Rate2 Acres3 Dose4

ST and IT 

Inhalation 

MOE 

(Baseline)5

Mitigation 

Level

M/L/A spray boom, 

handgun, or other suitable 

equipment mounted on a 

boat or vehicle, 

helicopter.

Aquatic Sites: For control of immersed, submersed and floating aquatic 

plants in aquatic sites such as ponds, lakes, reservoirs, non-irrigation canals 

and ditches which have little or no continuous outflow, marshes and 

wetlands, including broadleaf and woody vegetation on banks and shores 

within or adjacent to these and other aquatic sites.

3.9 0.08436 lb 

ae/gal

1,000 

gallons 0.00411 1,200

M/L/A Handheld sprayer

Cool season turfgrass, and on non-crop areas including industrial sites, rightsof-way (such as roadsides, electric utility and communication transmission 

lines, pipelines and railroads), non-irrigation ditch banks, natural areas (such 

as wildlife management areas, wildlife openings, wildlife habitats, recreation 

areas, campgrounds, trailheads and trails) and grazed areas in and around 

these sites

30 0.23 lb ae/gal 40 

gallons

0.00345

1,400

Flagger

Aerial spray app.

Rice

0.35

(baseline)

0.375 lb ae/A

350

0.000574 8,700

Range and pasture, forests and non-crop areas, including manufacturing and 

storage sites, rights-of-way such as electrical power lines, communication 

lines, pipelines, roadsides, railroads, fence rows, non-irrigation ditch banks, 

and around farm buildings; and applications to grazed areas, and 

establishment and maintenance of wildlife openings, and in Christmas tree 

plantations and aquatic sites. 

9 lb ae/A 0.0138 360

1. Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table”; Level of mitigation: Baseline, PPE (gloves), Eng. Controls.

2. Based on proposed labels.

3. Exposure Science Advisory Council Policy #9.1.

4. Inhalation Dose = Inhalation Unit Exposure (μg/lb)× Conversion Factor (0.001 mg/μg) × Application Rate (lb ae/acre) × Area Treated (A/day) x IAF (100 %) ÷ BW (80 kg).

5. Inhalation MOE = Inhalation NOAEL (5 mg/kg/day) ÷ Inhalation Dose (mg/kg/day).