UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

Date: 

Subject: 

September 18, 2013 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

Trinexapac-ethyl. Preliminary Occupational and Residential Exposure/Risk 

Assessment for Registration Review 

PC Code: I 12602 

Decision No.: lf';3f'1?; 

Petition No.: 

DP Barcode: D4/.J030 

Registration No.: 

Regulatory Action: Reg Review 

Risk Assessment Type: OccupationaVResidential Exposure Assessment Case No.: 7228 

TXRNo.: NA CAS No.: 95266-40-3 

MRIDNo.: NA 40CFR: 

From: 

Through: 

To: 

Introduction 

Monica Hawkins, Ph.D., M.P.H., Environmental Health ScientistJYl&v\J.,'Ctlt., ~ ~ Risk Assessment Branch VI 

Health Effects Division (7509P) 

Felecia Fort, Branch Chief --:l /)~~ /-

Risk Assessment Branch 6 ~ u 07 

Health Effects Division (7509P) 

and 

Kelly 

Ana Rivera-Lupianez, 

Lowe, ExpoSAC 

ExpoSAC 

Reviewer 

Reviewer 

#1 ~ #2 flvl-/v ~ 

Exposure Science Advisory Committee (ExpoSAC) I HED 

Sheila Piper, Senior Chemist/Risk Assessor 

Risk Assessment Branch VI 

Health Effects Division (7509P) 

Kaitlin Keller, Chemical Review Manager 

Risk Management and Implementation Branch 3 

Pesticide Re-Evaluation Division (7508P) 

As part of Registration Review, the Pesticide Re-evaluation Division (PRD) ofOPP requested 

that the Health Effects Division (HED) conduct an occupational and residential exposure 

Page I of41 
assessment, as needed, to estimate the risk to human health that will result from the currently 

registered uses oftrinexapac-ethyl. 

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; the Outdoor Residential Exposure Task Force 

(ORETF) database; the Agricultural Reentry Task Force (ARTF) database; the Residential SOPs 

(Turf/Lawn); and a chemical-specific turftransferable residue (TTR) study (MRID 45260201). 

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 [7/18/13). 

Page 2 of 41 
Page 3 of 41

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....................................................................................................... 7

4.0 Use Profile ......................................................................................................................... 10

5.0 Residential Exposure and Risk Estimates.......................................................................... 12

5.1 Residential Handler Exposure/Risk Estimates............................................................... 13

5.2 Residential Post-application Exposure/Risk Estimates.................................................. 17

5.3 Residential Risk Estimates for Use in Aggregate Assessment ...................................... 18

5.4 Spray Drift...................................................................................................................... 20

5.5 Residential Bystander Post-Application Inhalation Exposure ....................................... 20

6.0 Occupational Exposure and Risk Estimates ...................................................................... 21

6.1 Occupational Handler Exposure/Risk Estimates............................................................ 21

6.2 Occupational Post-application Exposure/Risk Estimates .............................................. 31

6.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates...................... 31

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates.......................... 31

Appendix A. Summary of Occupational and Residential Non-cancer Algorithms..................... 35

1.2 Residential Handler Dose Calculations.......................................................................... 35
Page 4 of 41

1.0 Executive Summary

Use Profile

Trinexapac–ethyl is a cyclohexadione plant growth regulator that is marketed as an emulsifiable 

concentrate, wettable powder packed in water-soluble bags, granule, and as a technical chemical 

used for formulation only. Trinexapac-ethyl has multiple end-use products that are registered for 

use on turf areas such as sod farms, golf courses, sports fields, cemeteries and similar areas, and 

on grasses grown for seed, sugarcane, and cereals (wheat, barley, oats, triticale). The labelrequired personal protective equipment (PPE) for occupational applicators and handlers is a 

long-sleeved shirt, long pants, shoes, and socks, chemical-resistant gloves, and protective 

eyewear. 

Hazard Profile

Since the previous human health risk assessment (D377921, S.Piper, 11/23/2011), no changes 

have been made to the hazard characterization for trinexapac-ethyl. Endpoints of concern for the 

incidental oral, inhalation, and dermal scenarios for children are not available from the 

trinexapac-ethyl toxicity studies (see rationale in Section 3, Hazard Characterization below). For 

short- and intermediate-term dermal and inhalation exposures for adults, the point of departure 

(POD) is from an oral developmental study in rabbits. The LOAEL (Lowest Observed Adverse 

Effect Level) from this study was 360 mg/kg/day based on a decrease in the mean number of 

fetuses/litter and an increase in post-implantation loss. The NOAEL (No Observed Adverse 

Effect Level) from this study was 60 mg/kg/day. A dermal absorption factor of 77.5 % was used 

for the exposure assessment based on information from a rat dermal penetration study (MRID 

42238105). An oral study was selected for the inhalation route because there was no inhalation 

study of appropriate duration, and based on a review by HASPOC, a route-specific inhalation 

toxicity study is not required at this time. The level of concern (LOC) for occupational and nonoccupational risk is for margins of exposure (MOEs) less (<) than 100. A body weight of 69 kg 

was used for the inhalation and dermal assessment since the endpoints were from a 

developmental toxicity study with fetal effects. Since the dermal and inhalation scenarios are 

based on the same study, they can be combined when assessing occupational and residential 

exposure. Trinexapac-ethyl is classified as “Not likely to be carcinogenic to humans.” 

Residential Exposure/Risk

HED determined that there is a potential for residential handler and post-application exposure to 

trinexapac-ethyl from the currently registered turf products. An updated residential handler and 

post-application assessment was conducted because HED recently updated the Standard 

Operating Procedures for Residential Pesticide Exposure Assessment 

(http://www.epa.gov/opp00001/science/EPA-OPP-HED_Residential%20SOPS_Feb2012.pdf) 

and body weights to be used in all human health assessments. The combined dermal plus 

inhalation risk estimates to residential handlers do not exceed HED’s LOC for all scenarios (i.e., 

MOEs ≥ 100); MOEs ranged from 240 to 21,000,000. The short-term dermal residential postapplication MOEs ranged from 450 to 61,000, and therefore, do not exceed HED’s LOC (MOEs

≥ 100). Chemical-specific TTR data are available for trinexapac-ethyl and were used in the 
Page 5 of 41

residential post-application exposure assessment in conjunction with standard default 

assumptions.

Occupational Exposure/Risk

HED determined that there is a potential for occupational handler and post-application exposure 

to trinexapac-ethyl from the currently registered products. The occupational handler assessment 

was completed assuming the maximum label application rate for each crop. The occupational 

handler exposure and risk estimates indicate that short- and intermediate-term dermal and 

inhalation combined MOEs are not of concern to HED (i.e., MOEs ≥ 100) with baseline attire 

and/or with the addition of gloves (as required on the labels). With baseline attire and/or gloves, 

the dermal plus inhalation MOEs range from 140 to 2,100,000. 

Chemical-specific TTR data are available for trinexapac-ethyl and were used in the occupational 

post-application exposure assessment to assess turf in conjunction with standard default 

assumptions to assess sugarcane, cereals (wheat, barley, oats, triticale), and grasses grown for 

seed. The occupational post-application dermal exposure and risk estimates indicate that shortand intermediate-term MOEs are not of concern to HED (i.e., MOEs ≥ 100) on the day of 

application, except for hand-harvesting sugarcane (MOE=87) where risk estimates are of concern 

until 2 days after application (MOE=110). The occupational post-application MOEs on the day 

of application range from 87 to 43,000. Based on HED’s occupational post-application exposure 

assessment, the restricted-entry interval (REI) for hand-harvesting sugarcane was estimated to be 

2 days for short- and intermediate-term exposure. However, HED does not recommend that 

sugarcane REI’s be changed on the trinexapac-ethyl labels at this time based on two main issues. 

One, almost all sugarcane harvesting in the United States is done mechanically. Two, the 

proposed trinexapac-ethyl labels have a 28-day pre-harvest interval (PHI) for sugarcane, so hand 

harvesting should not occur until after 28 days which is protective of the estimated REIs. 

Current trinexapac-ethyl labels have either no REI, 0 days, or a 4-hour REI. The trinexapacethyl technical material has been classified in Toxicity Category III for acute dermal, oral, and 

primary eye irritation, and Category IV for acute inhalation and primary skin irritation. 

Therefore, the acute toxicity categories for this chemical require a 12 hour REI under 40 CFR 

156.208 (c) (2) (iii). The Registration Division (RD) should ensure the proper REIs are put in 

place on the labels to reflect these requirements (D392798, M. Hawkins, 11/23/2011).

Based on the Agency's current practices, a quantitative non-cancer occupational post-application 

inhalation exposure assessment was not performed for trinexapac-ethyl at this time. If new 

policies or procedures are put into place, the Agency may revisit the need for a quantitative 

occupational post-application inhalation exposure assessment for trinexapac-ethyl.

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; the Outdoor Residential Exposure Task Force (ORETF) 

database; the ARTF database; the Residential SOPs (Turf/Lawn); and a chemical-specific TTR 

study (MRID 45260201) 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 
Page 6 of 41

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.

2.0 Risk Assessment Conclusions and Recommendations

2.1 Summary of Risk Estimates

There are no occupational/residential risk estimates of concern associated with the currently 

registered uses of trinexapac-ethyl.

2.2 Label Recommendations from Occupational/Residential Assessment 

The Registration Division (RD) should ensure the proper REIs are put in place considering the 

post-application assessment, the acute toxicity of trinexapac and the criteria for 4-hr REIs on the 

labels to reflect these requirements. (Hawkins, M., DP392798, 11/23/11).

2.3 Data Deficiencies and Requirements

Turf Transferable Residue (TTR): In accordance with the updated Part 158 data requirements 

(2007), a TTR study is required for all occupational (e.g., sod farms, golf courses, parks, and 

recreational areas) or residential turf uses. A TTR study (MRID 45260201) has been submitted 

and reviewed for trinexapac-ethyl. Therefore, there is not a data deficiency for this requirement.

Dislodgeable Foliar Residue (DFR): In accordance with the updated Part 158 data requirements 

(2007), one or more DFR studies are required when a pesticide has residential or occupational 

uses that could result in post-application dermal exposure. As part of the recent revision to the 

Health Effects Division’s 2012 Standard Operating Procedures for Residential Pesticide 

Exposure Assessment, HED analyzed a number of DFR studies and selected a new default value 

for the fraction of the application rate available to be dislodged after a foliar application (FAR). 

This default value is 25% and is based on an analysis of 19 DFR studies where the FAR value 

ranged from 2% to 89%. This value is recommended for use in both residential and occupational 

post-application assessments. Of the analyzed DFR studies, the maximum FAR value seen was 

89% or 3.6 times higher than the default residue transfer value. Therefore, the HED has decided 

that a calculated MOE of approximately 4 times higher than the level of concern (e.g., an MOE > 

400 if the LOC = 100) using the default dislodged residue values would provide an adequate 

margin of safety for any potentially higher residues seen in a chemical-specific DFR study 

(Guidance for Requiring/Waiving Turf Transferrable Residue (TTR) and Dislodgeable Foliar 

Residue (DFR) Studies. 6/7/2012, Exposure Science Advisory Council). A DFR study is

required for trinexapac-ethyl at this time since there are dermal MOEs less than 4 times the 

LOC based on default values for the fraction of application rate available for transfer after a 

foliar application.

 

1

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

http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 7 of 41

3.0 Hazard Characterization

Acute Toxicity

The acute toxicity for trinexapac-ethyl technical formulation was classified as Toxicity Category

III for acute oral, dermal, and eye irritation, and IV for acute inhalation and skin irritation. Table 

3.1 presents a summary of the acute toxicity information for trinexapac-ethyl.

Table 3.1. Acute Toxicity Profile - Trinexapac-ethyl (97%)

Guideline 

No. Study Type MRID Results Toxicity Category

870.1100 Acute oral [rat] 41563901

♂ LD50 = 4613 mg/kg

♀ LD50 = 4212 mg/kg

Combined LD50 = 4458 mg/kg

III

870.1200 Acute dermal [rabbit] 41563910 LD50 > 4000 mg/kg III

870.1300 Acute inhalation [rat] 41563912 LC50 ≥ 5.3 mg/L IV

870.2400 Acute eye irritation [rabbit] 41563914 Minimal irritant; cleared by 72 hours III

870.2500 Acute dermal irritation [rabbit] 41563916 Slightly irritating; cleared by day 7 IV

870.2600 Skin sensitization [guinea pig] 41869522 Not a dermal sensitizer N/A

Since the previous human health risk assessment (D377921, S.Piper, 11/23/2011), no changes 

have been made to the hazard characterization for trinexapac-ethyl. A NOAEL of 60 mg/kg/day 

was selected as the POD for short- and intermediate-term adult dermal and inhalation exposure. 

The LOAEL is 360 mg/kg/day based on a decrease in the mean number of fetuses/litter and an 

increase in post-implantation loss. The chronic dog study was also considered since it has a 

similar LOAEL (357 mg/kg/day). The NOAELs established in these two studies, however, are

2-fold different due to the dose-spread in the two studies. Therefore, the higher NOAEL of 60 

mg/kg/day from the rabbit developmental study (LOAEL 360 mg/kg/day) is protective of the 

effects observed (LOAEL 357 mg/kg/day) in the chronic dog study with NOAEL of 31.6 

mg/kg/day. In addition, although the 21-day rabbit dermal study did not result in systemic 

toxicity at the limit dose and suggests a dermal assessment is not warranted, this study is 

performed only in adult animals, not pregnant animals. It is currently unknown if a dermal study 

with pregnant rabbits would result in an in utero effect similar to that observed in the rabbit 

developmental study. Therefore, the use of the rabbit developmental study for the short- and 

intermediate-term adult dermal and inhalation scenarios is conservative and protective for these 

routes of exposure. Since the dermal and inhalation scenarios are based on the same study, they 

can be combined when assessing occupational and residential exposure.

The need for a subchronic inhalation study for trinexapac-ethyl was discussed by the Hazard and 

Science Policy Council (HASPOC) on June 20, 2013 (TXR 0056699). The HASPOC concluded 

that based on a weight-of-evidence approach, considering all the available hazard and exposure 

information for trinexapac-ethyl, a subchronic inhalation study is not needed at this time. 

The short- and intermediate-term dermal and inhalation endpoints selected for adults are only 

applicable to adults (females) because the endpoint is based on in utero effects. HED reviewed 

the full toxicological database for trinexapac-ethyl in an attempt to select endpoints for the 
Page 8 of 41

dermal and inhalation children scenarios; however, no appropriate endpoint was available for 

these scenarios based on the following reasons:

dermal irritation effects are mild after 21/28 days of exposure in the rabbit study,

dermal irritation effects after a single exposure disappear after seven days,

there are no systemic effects up to the limit dose in the dermal rabbit study,

there are no adverse toxicological effects (at doses close to the limit dose of 1000 

mg/kg/day) in the 2-generation reproductive study in rats or in the 

chronic/carcinogenicity studies in rats and mice, 

there is no maternal toxicity in the developmental toxicity studies in both rats and 

rabbits, and

there are no identifiable endpoints for the oral studies in the rat or rabbit.

An endpoint of concern for the incidental oral scenario is also not available from the available 

trinexapac-ethyl toxicity studies and the rationale for this conclusion is based on the following 

weight of evidence considerations: 

the toxicity observed during the appropriate duration of concern (short/intermediate 

term) were observed only at high doses [LOAELs = 900 mg/kg/day in the dog, 1000 

mg/kg/day in the rat, and 1212 mg/kg/day in the reproduction study],

the brain lesions observed in the chronic dog study are not appropriate for this 

scenario since the brain lesions were seen only at termination (i.e. after exposure for

1-year) and toxicity observed after chronic exposure is not appropriate for application 

to the short/intermediate term scenarios,

the brain lesions observed in the chronic study are not expected to occur after short 

term exposure due to the lack of similar lesions or associated toxicity (i.e., clinical 

neurologic signs) in the 90-day studies in rats or dogs,

the cause for concern for the brain lesions is low because of the minimal lesion 

severity, lack of associated changes (i.e., gliosis, myelin loss astrocyte hypertrophy, 

neuronal necrosis etc), and the non-specific nature of the lesions (i.e., focal 

vacuoles),

the overall toxicity profile of this chemical clearly shows that toxicity is observed 

only at high doses (lowest LOAEL = 360 mg/kg/day in the chronic dog study), and

the in utero endpoint identified in the rabbit study is not appropriate for this 

population of concern (children) (D392798, M.Hawkins, 11/23/2011).

The Agency’s LOC for risks (i.e., target level for MOEs) is defined by uncertainty factors. The 

Agency applies a factor of 10X to account for interspecies extrapolation to humans from the 

animal test species and another factor of 10X to account for intra-species sensitivity. HED 

previously concluded that the 10X FQPA Safety Factor for trinexapac-ethyl can be reduced to 

1X (D377921, S.Piper, 11/23/2011). The total uncertainty factor that has been applied to 

occupational and residential adult risk assessments is 100 for short- and intermediate-term 

dermal and inhalation exposures.
Page 9 of 41

Trinexapac-ethyl is classified as “Not likely to be carcinogenic to humans.” This is based on the 

lack of carcinogenic potential noted in the available studies. There is no concern for 

mutagenicity and clastogenicity. Quantification of cancer risk is not required.

Absorption

A dermal absorption factor of 77.5 % was used for the exposure assessment based on 

information from a rat dermal penetration study (MRID 42238105). The dermal absorption 

factor was estimated based on the sum of 56.5% absorbed after 10 hours in the low dose group 

(0.01 mg/cm2), in addition to 21% of applied dose that was associated with the application site. 

Since no inhalation absorption data are available, toxicity by the inhalation route is considered to 

be equivalent to the estimated toxicity by the oral route of exposure.

Body Weight

Since the dermal and inhalation PODs are based on developmental and/or fetal effects, the body 

weight appropriate for dermal and inhalation assessments is 69 kg.

Table 3.2 presents the selected points of departure for trinexapac-ethyl.

Table 3.2. Summary of Toxicological Doses and Endpoints for Trinexapac-ethyl for use in 

Occupational/Residential Human Health Risk Assessments.

Exposure/

Scenario

Point of 

Departure

Uncertainty/ 

FQPA Safety 

Factors

Level of Concern 

for Risk 

Assessment

Study and Toxicological Effects

Acute Dietary

(General Population, 

including Infants and 

Children)

No appropriate endpoint for the general population including infants and children

Incidental Oral 

(Short and 

Intermediate- Term )

No appropriate endpoint was available for the incidental oral scenario.

Dermal & Inhalation 

(Children)

Short and 

Intermediate-Term (1-

6 months)

No appropriate endpoint was available for the children’s dermal and inhalation scenarios.

Dermal & Inhalation 

(Adults)

Short and 

Intermediate-Term (1-

6 months)

NOAEL= 60 

mg/kg/day

Dermal 

absorption rate 

= 77.5% of 

oral absorption

Inhalation 

absorption rate 

= 100% of oral 

absorption

UFA= 10x

UFH = 10x

FQPA SF= 1x

Residential LOC 

for MOE = 100

Occupational 

LOC for MOE = 

100

Developmental rabbit study

MRID 41869524

LOAEL = 360 mg/kg, based on a 

decrease in mean number of 

fetuses/litter and an increase in postimplantation loss

Cancer (oral, dermal, 

inhalation)

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). FQPA SF = FQPA Safety Factor. 
Page 10 of 41

4.0 Use Profile 

Table 4.1 provides a summary of the registered uses of trinexapac-ethyl and represents the 

highest application rate for each of the trinexapac-ethyl formulations. Several of the trinexapacethyl labels did not provide the pounds (lb) active ingredient (ai) per gallon of product; therefore, 

HED made assumptions in order to convert the rates to lb ai/A. A detailed summary of the 

registered products and application rates is provided in an attached Excel spreadsheet.

Table 4.1 Trinexapac-ethyl Use Patterns and Formulations

Applic. Timing, 

Type, and 

Equip.

Formulation 

[EPA Reg. 

No.]

Applic. 

Rate (lb 

ai/A)

Max. Seasonal 

Applic. Rate 

(lb ai/A)

Max. 

Applic. 

per

Season

REI Use Directions and 

Limitations

Turf 

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Hand 

Gun Sprayers

12% ai, EC

Primo Liquid

(EPA Reg. No. 

100-729)

0.36 lb

ai/A

(0.017 lb 

ai/gallon; 

0.000008 

lb ai/ft2)

0.36 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Spray 

Gun

25.0 % ai, 

Primo WSB

WP in Water 

Soluble Bag

(EPA Reg. No. 

100-752)

0.34 lb 

ai/A

(0.016 lb 

ai/gallon)

0.34 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Turf (Edging/Banding)

Spreader, Shaker 

Can

.01 %-1.0 % ai,

Lawn Primo F, 

Granule, (EPA 

Reg. No.

100-931)

0.88 lb 

ai/A

(0.00002 

lb ai/ft2)

0.88 lb ai/A Multiple 0 days

Be sure the lawn has adequate 

fertility before using the 

product.

Backpack 

Sprayers, Hand 

Sprayers, Boom 

Sprayers, Spray 

Guns

12% ai, EC

Primo Liquid

(EPA Reg. No. 

100-729)

0.73 lb 

ai/A 0.73 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Spray 

Gun

25.0 % ai, 

Primo WSB,

WP in Water 

Soluble Bag

(EPA Reg. No. 

100-752)

0.68 lb 

ai/A 0.68 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Turf and Edging/Banding

Spreader, Shaker 

Can

0.39% ai,

The Andersons 

0.39% 

Trinexapac0.88 lb 

ai/A

0.88 lb ai/A Multiple 0 days Do not apply this product to 

grasses not listed on the label.
Page 11 of 41

Table 4.1 Trinexapac-ethyl Use Patterns and Formulations

Applic. Timing, 

Type, and 

Equip.

Formulation 

[EPA Reg. 

No.]

Applic. 

Rate (lb 

ai/A)

Max. Seasonal 

Applic. Rate 

(lb ai/A)

Max. 

Applic. 

per

Season

REI Use Directions and 

Limitations

ethyl + 

Fertilizer,

Granule,

(EPA Reg. No. 

9198-246)

Sod Farm

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Hand 

Gun Sprayers

12% ai, EC

Primo Liquid

(EPA Reg. No. 

100-729)

0.36 lb

ai/A 0.36 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Spray 

Gun, Aerial, 

Chemigation

25.0 % ai, 

Primo WSB,

WP in Water 

Soluble Bag

(EPA Reg. No. 

100-752)

0.34 lb 

ai/A 0.34 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Golf Course Fairways

Spreader, Shaker 

Can

0.39% ai,

The Andersons 

0.39% 

Trinexapacethyl + 

Fertilizer,

Granule,

(EPA Reg. No. 

9198-246)

0.44 lb 

ai/A 0.44 lb ai/A 0 days Do not apply this product to grasses not listed on the label.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Hand 

Gun Sprayers

12% ai, EC

Primo Liquid

(EPA Reg. No. 

100-729)

0.18 lb 

ai/A 0.18 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Spray 

Gun

25.0 % ai, 

Primo WSB,

WP in Water 

Soluble Bag

(EPA Reg. No. 

100-752)

0.17 lb 

ai/A 0.17 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Golf Course Greens

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Hand 

Gun Sprayers

11.3% ai, 

Microemulsion 

Concentrate

Primo Maxx

(EPA Reg. No. 

100-937)

0.07 lb 

ai/A 0.07 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.
Page 12 of 41

Table 4.1 Trinexapac-ethyl Use Patterns and Formulations

Applic. Timing, 

Type, and 

Equip.

Formulation 

[EPA Reg. 

No.]

Applic. 

Rate (lb 

ai/A)

Max. Seasonal 

Applic. Rate 

(lb ai/A)

Max. 

Applic. 

per

Season

REI Use Directions and 

Limitations

Spreader, Shaker 

Can

.01 %-1.0 % ai,

Lawn Primo F, 

Granule, (EPA 

Reg. No.

100-931)

0.07 lb 

ai/A 0.07 lb ai/A Multiple 0 days

Be sure the lawn has adequate 

fertility before using the 

product.

Back Pack, Hand 

Sprayers, Boom 

Sprayers, Spray 

Gun

25.0 % ai, 

Primo WSB, 

WP in Water 

Soluble Bag

(EPA Reg. No. 

100-752)

0.05 lb 

ai/A 0.05 lb ai/A Multiple 0 days

Do not apply this product 

through any type of irrigation 

system.

Grasses Grown For Seed

Aerial, Ground, 

Chemigation

12 %

Palisade EC, 

EC,

(EPA Reg. No. 

100-949) 

0.5 lb ai/A 0.5 lb ai/A 2 12 hours PHI = 35 days

Sugarcane

Aerial, Ground, 

Chemigation

12 %

Palisade EC, 

EC,

(EPA Reg. No. 

100-949)

0.31 lb 

ai/A 0.31 lb ai/A 2 12 hours PHI = 28 days

Cereals (Wheat, Barley, Oats, Triticale)

Aerial, Ground, 

Chemigation

12 %

Palisade EC, 

EC,

(EPA Reg. No. 

100-949)

0.1 lb ai/A 0.11 lb ai/A 2 12 hours PHI = 45 days.

5.0 Residential Exposure and Risk Estimates

This document addresses the potential residential exposure to trinexapac-ethyl from the currently 

registered turf products. Updated residential handler and post-application assessments were 

conducted because HED recently updated the Standard Operating Procedures for Residential 

Pesticide Exposure Assessment (http://www.epa.gov/opp00001/science/EPA-OPPHED_Residential%20SOPS_Feb2012.pdf) and body weights to be used in all human health 

assessments. Based on the updated assessments, the combined dermal plus inhalation risk

estimates to residential handlers do not exceed HED’s level of concern for all scenarios (i.e., 

MOEs ≥ 100). Short-term dermal post-application risk estimates were assessed for adults and 

children 11 to < 16 years old, and the residential post-application MOEs ranged from 450 to 

61,000 and therefore do not exceed HED’s LOC (MOEs ≥ 100). The revision of residential 

exposures will impact the human health aggregate risk assessment for trinexapac-ethyl.
Page 13 of 41

5.1 Residential 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 tasks related to applications and that 

exposures can vary depending on the specifics of each task. Residential handlers are addressed 

somewhat differently by HED as homeowners are assumed to complete all elements of an 

application without use of any protective equipment.

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

following scenarios: 

Mixing/Loading/Applying Liquid with Hose-End Sprayer,

Mixing/Loading/Applying Liquid with Manually-Pressurized Handwand,

Mixing/Loading/Applying Liquid with Sprinkler Can,

Mixing/Loading/Applying Liquid with Backpack,

Mixing/Loading/Applying Wettable Powders in Water-Soluble Packaging with Hose-end 

Sprayer,

Mixing/Loading/Applying Wettable Powders in Water-Soluble Packaging with 

Manually-Pressurized Handwand,

Mixing/Loading/Applying Wettable Powders in Water-Soluble Packaging with 

Backpack,

Applying Granules with Push-Type Rotary Spreader,

Applying Granules with Belly Grinder,

Applying Granules with Spoon,

Applying Granules with Cup,

Applying Granules with Hand Dispersal,

Applying Granules with Shaker Can.

Residential Handler Exposure Data and Assumptions

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

handler risk assessments. Each assumption and factor is detailed below.

Application Rate: The maximum application rates for the currently registered uses for 

trinexapac-ethyl are listed in Table 4.1.

Unit Exposures and Area Treated or Amount Handled: Unit exposure values and estimates for 

area treated or amount handled were taken from HED’s 2012 Residential SOPs2.

Exposure Duration: Residential handler exposure is expected to be short-term in duration. 

Intermediate-term exposures are not likely because of the intermittent nature of applications by 

homeowners.

Residential Handler Non-Cancer Exposure and Risk Estimate Equations

 

2 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Page 14 of 41

The algorithms used to estimate exposure and dose for residential handlers can be found in 

Appendix A and/or the 2012 Residential SOPs3.

Combining Exposures/Risk Estimates:

Dermal and inhalation risk estimates were combined in this assessment, since the toxicological 

effects for these exposure routes were similar. Dermal and inhalation risk estimates were 

combined using the following formula:

Total MOE = Point of Departure (mg/kg/day) ÷ Combined Dermal + Inhalation dose (mg/kg/day)

Summary of Residential Handler Non-Cancer Exposure and Risk Estimates

The combined dermal and inhalation MOEs for residential handlers ranged from 240 to 

21,000,000. The MOEs for all of the scenarios exceed the LOC of 100 which indicate that the 

residential handler exposure risk estimates are not of concern. The residential handler exposures 

and MOEs are calculated as detailed in Table 5.1.1.

 

3 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Page 15 of 41

Table 5.1.1. Residential Handler Non-cancer Exposure and Risk Estimates for Trinexapac-ethyl.

Exposure Scenario Level of 

Concern

Dermal Unit 

Exposure

(mg/lb ai)

Inhalation 

Unit 

Exposure

(mg/lb ai)

Maximum 

Application 

Rate1

Area Treated or 

Amount 

Handled Daily2

Dermal Inhalation Total

Dose 

(mg/kg/day)3 MOE4 Dose (mg/kg/day)5 MOE6 MOE7

Mixer/Loader/Applicator

Lawns/Turf Liquid with 

Hose-End Sprayer 100 13.4 0.022 0.36 lb ai/A 0.5 acres 0.027 2,200 0.000058 1,000,000 2,200

Lawns/Turf Liquid with 

Manually-Pressurized 

Handwand

100 63 0.018 0.017 lb 

ai/gallon 5 gallons 0.06 1,000 0.000022 2,700,000 1,000

Lawns/Turf Liquid with 

Sprinkler Can 100 13.4 0.022

0.000008 lb

ai/ft 2 1,000 ft2

0.0012 50,000 0.0000026 24,000,000 50,000

Lawns/Turf Liquid with 

Backpack 100 130 0.14 0.017 lb ai/gallon 5 gallons 0.12 480 0.00017 350,000 480

Lawns/Turf Liquid with 

Backpack 

(Edging/Banding)

100 130 0.14 0.034 lb 

ai/gallon 5 gallons 0.2482 240 0.00034 170,000 240

Lawns/Turf Wettable 

Powders in WaterSoluble Packaging with 

Hose-End Sprayer

100 6.26 0.034 0.34 lb ai/A 0.5 acres 0.012 5,000 0.000084 720,000 5,000

Lawns/Turf Wettable 

Powders in WaterSoluble Packaging with 

Manually-Pressurized 

Handwand

100 63 0.018 0.016 lb 

ai/gallon 5 gallons 0.057 1,100 0.000021 2,900,000 1,100

Lawns/Turf Wettable 

Powders in WaterSoluble Packaging with 

Backpack

100 63 0.018 0.016 lb 

ai/gallon 5 gallons 0.057 1,100 0.000021 2,900,000 1,100

Lawns/Turf Granule 

with Push-Type Rotary 

Spreader

100 0.81 0.0026 0.88 lb ai/A 0.5 acres 0.004 15,000 0.000017 3,600,000 15,000

Lawns/Turf Granule 

with Belly Grinder 100 360 0.039

0.00002 lb

ai/ft2 1,200 ft2

0.097 620 0.000014 4,400,000 620

Lawns/Turf Granule 

with Spoon 100 6.2 0.087

0.00002 lb

ai/ft2

100 ft20.00014 430,000 0.0000025 24,000,000 420,000

Lawns/Turf Granule 100 0.11 0.013 0.00002 lb 100 ft2

0.0000025 24,000,000 0.00000038 160,000,000 21,000,000
Page 16 of 41

Table 5.1.1. Residential Handler Non-cancer Exposure and Risk Estimates for Trinexapac-ethyl.

Exposure Scenario Level of 

Concern

Dermal Unit 

Exposure

(mg/lb ai)

Inhalation 

Unit 

Exposure

(mg/lb ai)

Maximum 

Application 

Rate1

Area Treated or 

Amount 

Handled Daily2

Dermal Inhalation Total

Dose 

(mg/kg/day)3 MOE4 Dose (mg/kg/day)5 MOE6 MOE7

with Cup ai/ft2

Lawns/Turf Granule 

with Hand Dispersal 100 160 0.38

0.00002 lb

ai/ft2 100 ft2

0.0036 17,000 0.000011 5,400,000 17,000

Lawns/Turf Granule 

with Shaker Can 100 0.11 0.013

0.00002 lb

ai/ft2

100 ft20.0000025 24,000,000 0.00000038 160,000,000 21,000,000

1 Based on currently registered trinexapac-ethyl labels.

2 Based on HED’s 2012 Residential SOPs (http://www.epa.gov/pesticides/science/residential-exposure-sop.html).

3 Dermal Dose = Dermal Unit Exposure (mg/lb ai) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A/day or gallons/day) × Dermal Absorption Factor 

(77.5%) ÷ Body Weight (69 kg).

4 Dermal MOE = Dermal NOAEL (60 mg/kg/day) ÷ Dermal Dose (mg/kg/day).

5 Inhalation Dose = Inhalation Unit Exposure (mg/lb ai) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A/day or gallons/day) ÷ Body Weight (69 kg).

6 Inhalation MOE = Inhalation NOAEL (60 mg/kg/day) ÷ Inhalation Dose (mg/kg/day).

7 Total MOE = NOAEL (60 mg/kg/day) ÷ (Dermal Dose + Inhalation Dose) 
Page 17 of 41

5.2 Residential Post-application Exposure/Risk Estimates

There is the potential for post-application exposure for individuals exposed as a result of being in 

an environment that has been previously treated with trinexapac-ethyl. Although there is the 

potential for dermal and oral post-application exposure to children, no dermal or oral exposure 

endpoints were selected (see rationale in Section 3, Hazard Characterization above). Therefore, 

a quantitative dermal and oral post-application assessment for children was not conducted. 

The quantitative exposure/risk assessment for residential post-application exposures is based on 

the following scenarios: 

Adults (dermal) performing high contact yard work on treated turf,

Adults (dermal) mowing treated turf, and

Adults (dermal) playing golf on treated turf.

Child 11 to < 16 years old (dermal) playing golf on treated turf

Child 11 to < 16 years old (dermal) mowing treated turf

Residential Post-application Exposure Data and Assumptions

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

post-application risk assessment. Each assumption and factor is detailed in the 2012 Residential 

SOPs4. In addition, chemical-specific residue data from a TTR study (MRID No. 45260201)

was used to estimate day zero residues for the dermal post-application exposure assessments

from use of liquid formulations. In the TTR study (MRID No. 45260201), the test sites

consisted of plots located in Georgia, California, and Indiana treated with a microemulsion

formulation. The Georgia site resulted in the highest average predicted day 0 residue value of 

0.031 ug/cm2but this was based on the edging/banding application rate of 0.69 lb ai/A. 

Therefore, HED adjusted the residue value of 0.031 ug/cm2for the maximum broadcast turf rates

of 0.36 and 0.88 lb ai/A for liquid and granular formulations, respectively, and the maximum 

golf course rates of 0.18 and 0.44 lb ai/A, for liquid and granular formulations, respectively, 

which resulted in predicted day 0 residue values of 0.016 and 0.008 ug/cm2for the liquid 

formulations and 0.040 and 0.020 ug/cm2for the granular formulations (See Appendix B for 

more details). Chemical-specific residue data from the TTR study (MRID No. 45260201) was 

used to assess residential post-application risk estimates from exposure to the liquid and granular 

formulations. The exposure potential to a granular formulation is expected to be less than that 

from a liquid formulation; therefore, the assessment of dermal exposure from the granular

formulation should be considered a conservative assessment.

Residential Post-application Non-Cancer Exposure and Risk Equations

The algorithms used to estimate residential post-application exposure and dose can be found in 

Appendix A and/or the 2012 Residential SOPs5.

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

 

4 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html

5 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Page 18 of 41

The residential post-application dermal MOEs ranged from 450 to 61,000 and therefore do not 

exceed HED’s LOC (MOEs ≥ 100). A summary of the residential post-application 

exposures/risk estimates is presented in Table 5.2.1.

Table 5.2.1 Residential Post-application Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl.

Lifestage

Post-application Exposure 

Scenario TTR

(ug/cm2)

1

Dose 

(mg/kg/day)2 MOEs3

Use Site Activity / Route 

of Exposure

Sprays

Child 11 to < 

16 years old Turf Golf Course (Dermal) 0.008 0.002 31,000

Child 11 to 

16 years old Turf Mowing (Dermal) 0.016 0.001 61,000

Adult Turf 

High Contact 

Lawn Activities 

(Dermal)

0.016 0.049 1,200

Mowing (Dermal) 0.016 0.001 61,000

Golf Course 

(Dermal) 0.008 0.002 31,000

Granular Formulation

Child 11 to < 

16 years old Turf Golf Course

(Dermal) 0.020 0.005 13,000

Child 11 to 

16 years old Turf Mowing (Dermal) 0.040 0.002 25,000

Adult Turf 

High Contact 

Lawn Activities 

(Dermal)

0.040 0.135 450

Mowing (Dermal) 0.040 0.002 24,000

Golf Course 

(Dermal) 0.020 0.005 13,000

1 TTR= chemical-specific data from MRID 45260201 for the Georgia site adjusted for differences in application rates (0.36 lb ai/A for 

residential turf and 0.18 lb ai/A for golf courses). See Appendix B for more information regarding the available data.

2 Dose (mg/kg/day) equations: See Appendix A and Appendix B for inputs.

3 MOE = POD (60 mg/kg/day) ÷ Dose (mg/kg/day).

5.3 Residential Risk Estimates for Use in Aggregate Assessment

Table 5.3.1 reflects the residential risk estimates that are recommended for use in the aggregate 

assessment for trinexapac-ethyl. 

The recommended residential exposure for use in the adult aggregate assessment reflects 

dermal and inhalation exposure from handler exposure to sprays that are applied on turf

with backpack sprayers (edging/banding), which resulted in a MOE of 240. 

The recommended residential exposure use in the child aggregate assessment reflects 

dermal exposure from mowing turf that has been treated with a granular formulation, 

which resulted in a MOE of 13,000.
Page 19 of 41

Table 5.3.1. Recommendations for the Residential Exposures for the Trinexapac-ethyl Aggregate Assessment.

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

Short-Term

Adult Female 0.2482 0.00034 0.249 240 170,000 240 0.135 N/A N/A 0.135 450 N/A N/A 450

Child 11 to 16 

years old N/A N/A N/A N/A N/A N/A 0.005 N/A N/A 0.005 13,000 N/A N/A 13,000

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

2 Residential Handler Dose = the highest handler dose for each applicable lifestage of all scenarios assessed from Table 5.1.1. Total = dermal + inhalation.

3 Residential Handler MOE = the MOEs associated with the highest doses identified in Table 5.1.1. Total = 1 ÷ (1/Dermal MOE) + (1/Inhalation MOE).

4 Residential Post-application Dose = the highest post-application dose for each applicable lifestage of all scenarios assessed from Table 5.2.1. Total = dermal + inhalation + incidental oral, where 

applicable.

5 Residential Post-application MOE = the MOEs associated with the highest doses identified in Table 5.2.1. Total = 1 ÷ (1/Dermal MOE) + (1/Inhalation MOE) + (1/Incidental oral MOE). 
Page 20 of 41

5.4 Spray Drift

Off-target movement of pesticides can occur via many types of pathways and it is governed by a 

variety of factors. Sprays that are released and do not deposit in the application area end up offtarget and can lead to exposures to those it may directly contact. They can also deposit on 

surfaces where contact with residues can eventually lead to indirect exposures (e.g., children 

playing on lawns where residues have deposited next to treated fields). The potential risk 

estimates from these residues can be calculated using drift modeling coupled with methods 

employed for residential risk assessments for turf products.

The approach to be used for quantitatively incorporating spray drift into risk assessment is based 

on a premise of compliant applications which, by definition, should not result in direct exposures 

to individuals because of existing label language and other regulatory requirements intended to 

prevent them.6 Direct exposures would include inhalation of the spray plume or being sprayed 

directly. Rather, the exposures addressed here are thought to occur indirectly through contact 

with impacted areas, such as residential lawns, when compliant applications are conducted. 

Given this premise, exposures for children (1 to 2 years old) and adults who have contact with 

turf where residues are assumed to have deposited via spray drift thus resulting in an indirect 

exposure are the focus of this analysis analogous to how exposures to turf products are 

considered in risk assessment. 

Several trinexapac-ethyl products have existing labels for use on turf, thus it was considered 

whether the risk assessment for that use may be considered protective of any type of exposure 

that would be associated with spray drift. It should be noted that the registered residential uses 

on turf result in exposure greater than potential exposure from spray drift; therefore, no new 

residential assessment for spray drift needs to be completed. If the maximum application rate on 

crops adjusted by the amount of drift expected is less than or equal to existing turf application 

rates, the existing turf assessment is considered protective of spray drift exposure. The proposed 

maximum single application rate of trinexapac-ethyl on grasses grown for seed is 0.5 lb ai/acre. 

According to the Tier 1 output from the groundboom spray profile of the AgDrift model, 

trinexapac-ethyl passed the spray drift screening because the maximum application rate to a crop 

target site (grasses grown for seed) multiplied by the adjustment factor for drift of 0.26 is less 

than the direct spray residential turf application rate (0.36 lb ai/A)7. The turf post-application 

MOEs have been previously assessed and are based on the revised SOPs for Residential 

Exposure Assessment (see above in Section 5.2). 

5.5 Residential Bystander Post-Application Inhalation Exposure

Based on the Agency's current practices, a quantitative post-application inhalation exposure 

assessment was not performed for trinexapac-ethyl at this time primarily because of the low 

acute inhalation toxicity (Toxicity Category III and IV). However, volatilization of pesticides 

may be a source of post-application inhalation exposure to individuals nearby pesticide 

 

6 This approach is consistent with the requirements of the EPA’s Worker Protection Standard which, 

when included on all labels, precludes direct exposure pathways.

7

0.5 lb ai/A x 0.26 = 0.13 lb ai/A
Page 21 of 41

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, 20108. The Agency is 

in the process of evaluating the SAP report and may, as appropriate, develop policies and 

procedures to identify the need for and, subsequently, the way to incorporate post-application 

inhalation exposure into the Agency's risk assessments. If new policies or procedures are 

developed, the Agency may revisit the need for a quantitative post-application inhalation 

exposure assessment for trinexapac-ethyl.

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 protection used by a handler can cause exposure levels to differ in a 

manner specific to each application event. 

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 currently 

registered uses. The quantitative exposure/risk assessment developed for occupational handlers 

is based on the following scenarios: 

Mixing/Loading Granules for Tractor Drawn Spreader Applications

Mixing/Loading Liquids for Aerial Applications

Mixing/Loading Liquids for Chemigation

Mixing/Loading Liquids for Groundboom Applications

Mixing/Loading Wettable Powders in Water Soluble Bags for Aerial Applications

Mixing/Loading Wettable Powders in Water Soluble Bags for Chemigation

Mixing/Loading Wettable Powders in Water Soluble Bags for Groundboom Applications

Applying Sprays for Aerial Applications

Applying Sprays for Groundboom Applications

Applying Granules for Tractor Drawn Spreader Applications

Flagging (Sprays) during Aerial Applications

Mixing/Loading/Applying Liquids for Backpack Applications

Mixing/Loading/Applying Liquids for Manually-Pressurized Handwand Applications

Mixing/Loading/Applying Liquids for Mechanically-Pressurized Handgun Applications

Mixing/Loading/Applying Wettable Powders in Water Soluble Bags for Backpack 

Applications

Mixing/Loading/Applying Wettable Powders in Water Soluble Bags for ManuallyPressurized Handwand Applications

Mixing/Loading/Applying Wettable Powders in Water Soluble Bags for MechanicallyPressurized Handgun Applications

 

8 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html
Page 22 of 41

Loading/Applying Granules for Belly Grinder Applications

Loading/applying granules for Rotary Spreader Applications

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 application rates for the currently registered uses of trinexapacethyl, as presented in Table 4.1, were used to estimate occupational handler exposure.

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, the Outdoor Residential Exposure Task Force 

(ORETF) database, 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 Table9”, 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 website10.

Area Treated or Amount Handled: 

Tractor-drawn spreader applications for golf course (fairways, tees, greens): 40 acres

Tractor-drawn spreader applications for golf course (tees and greens only): 5 acres

Aerial applications for typical crops: 350 acres

Aerial applications for high acre crops: 1200 acres

Chemigation applications for typical and high acre crops: 350 acres

Groundboom applications for golf course (tees and greens only): 5 acres

Groundboom applications for golf course (fairways, tees, greens): 40 acres

Groundboom applications for typical crops: 80 acres

Groundboom applications for high acre crops: 200 acres 

Flagging for aerial applications: 350 acres

Backpack applications: 40 gallons

Manually-pressurized handgun: 40 gallons

Mechanically-pressurized handgun: 5 acres

Belly grinder applications: 1 acre

Rotary spreader application: 5 acres

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 

 

9 Available: http://www.epa.gov/opp00001/science/handler-exposure-table.pdf

10 Available: http://www.epa.gov/pesticides/science/handler-exposure-data.html
Page 23 of 41

pesticide, and the cultural practices surrounding that use site. For most agricultural uses, it is 

reasonable to believe that occupational handlers will not apply the same chemical every day for 

more than a one-month time frame; however, there may be a large agribusiness and/or 

commercial applicators who may apply a product over a period of weeks (e.g., completing 

multiple applications for multiple clients within a region). 

For trinexapac-ethyl, based on the currently registered uses, short- and intermediate-term

exposure is expected for handlers. The short- and intermediate-term endpoints and PODs are the 

same for each exposure route, therefore only short-term handler exposures were estimated, and 

are considered protective for intermediate-term exposure and risk. Long-term exposures are not 

expected.

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

calculated for various levels of personal protective equipment (PPE). Results are presented for 

“baseline,” defined as a single layer of clothing consisting of a long sleeved shirt, long pants, 

shoes plus socks, no protective gloves, and no respirator, as well as baseline with various levels 

of PPE as necessary (e.g., gloves, respirator, etc). The trinexapac-ethyl product labels direct 

mixers, loaders, applicators and other handlers to wear long-sleeved shirt, long pants, shoes, and 

socks, chemical-resistant gloves, and protective eyewear.

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:

Dermal and inhalation risk estimates were combined in this assessment, since the toxicological 

effects for these exposure routes were similar. Dermal and inhalation risk estimates were 

combined using the following formula:

Total MOE = Point of Departure (mg/kg/day) ÷ Combined dermal + inhalation dose (mg/kg/day)

Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates

The short- and intermediate-term risk estimates for occupational handlers are included in Table 

6.1.1. All dermal and inhalation occupational handler scenarios are above HED’s LOC (MOEs 

≥ 100) with baseline attire and/or gloves and engineering control (i.e., enclosed cockpits) for 

aerial applications. With baseline attire and/or gloves, the dermal plus inhalation MOEs range 

from 140 to 2,100,000.

The Agency matches quantitative occupational exposure assessment with appropriate 

characterization of exposure potential. While HED presents quantitative risk estimates for human 

flaggers where appropriate, agricultural aviation has changed dramatically over the past two 

decades. According to the 2012 National Agricultural Aviation Association (NAAA) survey of 

their membership, the use of GPS for swath guidance in agricultural aviation has grown steadily 

from the mid 1990’s. Over the same time period, the use of human flaggers for aerial pesticide

applications has decreased steadily from ~15% in the late 1990’s to only 1% in the most recent 
Page 24 of 41

(2012) NAAA survey. The Agency will continue to monitor all available information sources to 

best assess and characterize the exposure potential for human flaggers in agricultural aerial 

applications.

HED has no data to assess exposures to pilots using open cockpits. The only data available is 

for exposure to pilots in enclosed cockpits. Therefore, risks to pilots are assessed using the 

engineering control (enclosed cockpits) and baseline attire (long-sleeve shirt, long pants, shoes, 

and socks); per the Agency’s Worker Protection Standard stipulations for engineering controls, 

pilots are not required to wear protective gloves for the duration of the application. With this 

level of protection, there are no risk estimates of concern for applicators.
Page 25 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Mixing/Loading Granules

Tractor-Drawn Spreader 

Application

Golf Course 

(Fairways, 

Tees, Greens)

8.4 1.7 0.44 40 0.00166 36,000 0.000433 140,000 29,000

Golf Course 

(Tees and 

Greens Only)

8.4 1.7 0.44 5 0.000208 290,000 0.0000542 1,100,000 230,000

Mixing/Loading Liquids

Aerial Application

Sod 220 0.219 0.36 350 0.314 190 0.000404 150,000 190

Grasses Grown 

For Seed 220 0.219 0.5 350 0.432 140 0.000555 110,000 140

Sugarcane 220 0.219 0.31 350 0.268 220 0.000345 170,000 220

Cereals (Wheat, 

Barley, Oats, 

Triticale)

220 0.219 0.11 1200 0.326 180 0.000419 140,000 180

Chemigation Application

Sod 220 0.219 0.36 350 0.314 190 0.000404 150,000 190

Grasses Grown 

For Seed 220 0.219 0.5 350 0.432 140 0.000555 110,000 140

Sugarcane 220 0.219 0.31 350 0.268 220 0.000345 170,000 220

Cereals (Wheat, 

Barley, Oats, 

Triticale)

220 0.219 0.11 350 0.0951 630 0.000122 490,000 630

Groundboom Application

Golf Course 

(Tees and 

Greens Only)

220 0.219 0.07 5 0.000865 69,000 0.00000111 54,000,000 69,000

Golf Course 

(Fairways, 

Tees, Greens)

220 0.219 0.18 40 0.018 3,300 0.000023 2,600,000 3,300

Sod 220 0.219 0.36 80 0.072 830 0.0000925 650,000 830

Grasses Grown 

For Seed 220 0.219 0.5 80 0.0988 610 0.000127 470,000 610
Page 26 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Sugarcane 220 0.219 0.31 80 0.0613 980 0.0000787 760,000 980

Cereals (Wheat, 

Barley, Oats, 

Triticale)

220 0.219 0.11 200 0.0544 1,100 0.0000699 860,000 1,100

Mixing/Loading Wettable Powders In Water Soluble Packaging

Aerial Application Sod 9.8 (EC) 0.24 (EC) 0.34 350 0.0131 (EC) 4,600 

(EC) 0.000414 (EC) 140,000 (EC) 4,500 (EC)

Chemigation Application Sod 9.8 (EC) 0.24 (EC) 0.34 350 0.0131 (EC) 4,600 

(EC) 0.000414 (EC) 140,000(EC) 4,500 (EC)

Groundboom

Golf Course 

(Tees and 

Greens Only)

9.8 (EC) 0.24 (EC) 0.05 5

0.0000275

(EC)

2,200,000

(EC)

0.00000087

(EC)

69,000,000

(EC)

2,100,000

(EC)

Groundboom

Golf Course 

(Fairways, 

Tees, Greens)

9.8 (EC) 0.24 (EC) 0.17 40 0.000748

(EC)

80,000

(EC)

0.0000236

(EC)

2,500,000

(EC)

78,000

(EC)

Groundboom Sod 9.8 (EC) 0.24 (EC) 0.34 80 0.003 (EC) 20,000

(EC)

0.0000946

(EC)

630,000

(EC)

19,000

(EC)

Appling Sprays

Aerial Application

Sod 2.08 (EC) 0.0049 (EC) 0.36 350 0.00298

(EC)

20,000

(EC)

0.00000904

(EC)

6,600,000

(EC)

20,000

(EC)

Grasses Grown 

For Seed 2.08 (EC) 0.0049 (EC) 0.5 350 0.00409

(EC)

15,000

(EC) 0.0000124(EC) 4,800,000(EC)

15,000

(EC)

Sugarcane 2.08 (EC) 0.0049 (EC) 0.31 350 0.00254

(EC)

24,000

(EC)

0.00000771

(EC) 7,800,000(EC) 24,000(EC)

Cereals (Wheat, 

Barley, Oats, 

Triticale)

2.08 (EC) 0.0049 (EC) 0.11 1200 0.00309

(EC)

19,000

(EC)

0.00000938

(EC)

6,400,000

(EC)

19,000

(EC)

Groundboom Application

Golf Course 

(Tees and 

Greens Only)

78.6 0.34 0.07 5 0.000309 190,000 0.00000172 35,000,000 190,000

Golf Course 

(Fairways, 

Tees, Greens)

78.6 0.34 0.18 40 0.00642 9,300 0.0000359 1,700,000 9,200
Page 27 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Sod 78.6 0.34 0.36 80 0.0257 2,300 0.000143 420,000 2,300

Grasses Grown 

For Seed 78.6 0.34 0.5 80 0.0353 1,700 0.000197 300,000 1,700

Sugarcane 78.6 0.34 0.31 80 0.0219 2,700 0.000122 490,000 2,700

Cereals (Wheat, 

Barley, Oats, 

Triticale)

78.6 0.34 0.11 200 0.0194 3,100 0.000108 560,000 3,100

Applying Granules

Tractor-Drawn Spreader 

Application

Golf Course 

(Fairways, 

Tees, Greens)

9.9 1.2 0.44 40 0.00195 31,000 0.000306 200,000 27,000

Tractor-Drawn Spreader 

Application

Golf Course 

(Tees and 

Greens Only)

9.9 1.2 0.44 5 0.000245 240,000 0.0000383 1,600,000 210,000

Flagger

Aerial Application

Sod 11 0.35 0.36 350 0.0157 3,800 0.000646 93,000 3,700

Grasses Grown 

For Seed 11 0.35 0.5 350 0.0217 2,800 0.000888 68,000 2,700

Sugarcane 11 0.35 0.31 350 0.0134 4,500 0.000551 110,000 4,300

Cereals (Wheat, 

Barley, Oats, 

Triticale)

11 0.35 0.11 350 0.00476 13,000 0.000196 310,000 12,000

Mixing/Loading/Appling Liquids

Backpack Application

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

8260 2.58 0.017 40 0.0631 950 0.0000254 2,400,000 950

Manually –Pressurized 

Handwand

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

100000

(baseline)

30 0.017 40

0.764

(baseline)

79

(baseline)

0.000296 200,000

79

(baseline)

430

(with gloves)

0.00328

(with gloves)

18,000

(with 

17,000

(with 
Page 28 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

gloves) gloves)

Backpack Application

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

8260 2.58 0.03 40 0.11 540 0.0000449 1,300,000 540

Manually –Pressurized 

Handwand

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

100000

(baseline)

30 0.03 40

1.35

(baseline)

44

(baseline)

0.000522 110,000

44

(baseline)

430

(with gloves)

0.0058

(with gloves)

10,000

(with 

gloves)

9,200

(with 

gloves)

Mechanically-Pressurized 

Handgun

Golf Course 

(Tees and 

Greens Only)

1140 1.9 0.07 5 0.00448 13,000 0.00000964 6,200,000 13,000

Mechanically-Pressurized 

Handgun

Golf Course 

(Fairways, 

Tees, Greens)

1140 1.9 0.18 5 0.0117 5,100 0.0000251 2,400,000 5,100

Mechanically-Pressurized 

Handgun

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

1140 1.9 0.36 5 0.0233 2,600 0.0000501 1,200,000 2,600

Mechanically-Pressurized 

Handgun

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

1140 1.9 0.73 5 0.0467 1,300 0.000101 590,000 1,300

Mixing/Loading/Applying Wettable Powders In Water Soluble Packaging

Backpack Application

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

8260 2.58 0.016 40 0.0594 1,000 0.0000239 2,500,000 1,000

Manually –Pressurized 

Handwand

Landscaping 

Turf (Lawns, 

Athletic Fields, 

100000

(baseline) 30 0.016 40

0.719

(baseline)

83

(baseline) 0.000278 220,000

83

(baseline)

430 0.00309 19,000 17,000
Page 29 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Parks, etc.) (with gloves) (with gloves) (with 

gloves)

(with

gloves)

Backpack Application

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

8260 2.58 0.03 40 0.11 540 0.0000449 1,300,000 540

Manually –Pressurized 

Handwand

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

100000

30 0.03 40

1.35

(baseline)

44

(baseline)

0.000522 110,000

44

(baseline)

430

(with gloves)

0.0058

(with gloves)

10,000

(with 

gloves)

9,200

(with 

gloves)

Mechanically-Pressurized 

Handgun

Golf Course 

(Tees and 

Greens Only)

1350 18 0.05 5 0.0038 16,000 0.0000652 920,000 16,000

Mechanically-Pressurized 

Handgun

Golf Course 

(Fairways, 

Tees, Greens)

1350 18 0.17 5 0.0129 4,700 0.000222 270,000 4,600

Mechanically-Pressurized 

Handgun

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

1350 18 0.34 5 0.0258 2,300 0.000443 140,000 2,300

Mechanically-Pressurized 

Handgun

Edging/Banding 

for Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

1350 18 0.68 5 0.0516 1,200 0.000887 68,000 1,200

Loading/Applying Granules

Belly Grinder Application

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

10000 62 0.88 1 0.0988 610 0.000791 76,000 610

Rotary Spreader 

Application

Golf Course 

(Tees and 440 10 0.44 5 0.0109 5,500 0.000319 190,000 5,300
Page 30 of 41

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Trinexapac-ethyl. 

Exposure Scenario Crop or Target

Dermal Unit 

Exposure (μg/lb 

ai)1

Inhalation Unit 

Exposure (μg/lb 

ai)1

Maximum 

Application 

Rate2

Area 

Treated or 

Amount 

Handled 

Daily3

Dermal Inhalation Total

Mitigation Level Mitigation Level Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day)6 MOE7 MOE8

Greens Only)

Rotary Spreader 

Application

Golf Course 

(Fairways, 

Tees, Greens)

440 10 0.44 5 0.0109 5,500 0.000319 190,000 5,300

Rotary Spreader 

Application

Landscaping 

Turf (Lawns, 

Athletic Fields, 

Parks, etc.)

440 10 0.88 5 0.0218 2,800 0.000638 94,000 2,700

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2013); Level of mitigation: Baseline (single layer of clothing, no gloves, no respirator), Baseline 

with gloves, or Eng. Controls (EC; closed cockpit) for aerial applicators.

2 Based on currently registered labels.

3 Exposure Science Advisory Council Policy #9.1.

4 Dermal Dose = Dermal Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) × DAF (77.5%) ÷ BW 

(69 kg).

5 Dermal MOE = Dermal NOAEL (60 mg/kg/day) ÷ Dermal Dose (mg/kg/day).

6 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre or gal) × Area Treated or Amount Handled (A or gal/day) ÷ BW (69 kg).

7 Inhalation MOE = Inhalation NOAEL (60 mg/kg/day) ÷ Inhalation Dose (mg/kg/day).

8 Total MOE = NOAEL (60 mg/kg/day) ÷ Dermal Dose + Inhalation Dose.
Page 31 of 41

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

Based on the Agency's current practices, a quantitative post-application inhalation exposure 

assessment was not performed for trinexapac-ethyl at this time primarily because of the low 

acute inhalation toxicity (Toxicity Category III and IV). However, 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, 201011. The Agency is in the process of evaluating 

the SAP report as well as available post-application inhalation exposure data generated by the 

ARTF and may, as appropriate, develop policies and procedures, to identify the need for and, 

subsequently, the way to incorporate occupational post-application inhalation exposure into the 

Agency's risk assessments. If new policies or procedures are put into place, the Agency may 

revisit the need for a quantitative occupational post-application inhalation exposure assessment 

for trinexapac-ethyl.

Although a quantitative occupational post-application inhalation exposure assessment was not 

performed, an inhalation exposure assessment was performed for occupational/commercial 

handlers. Handler exposure resulting from application of pesticides outdoors is likely to result in 

higher exposure than post-application exposure. Therefore, it is expected that these handler 

inhalation exposure estimates would be protective of most occupational post-application 

inhalation exposure scenarios.

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates

Occupational Post-application Dermal Exposure Data and Assumptions

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

post-application risk assessments. Each assumption and factor is detailed below on an individual 

basis.

 

11 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html
Page 32 of 41

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

days to six months as intermediate-term. For trinexapac-ethyl, based on the currently registered 

uses, short- and intermediate-term exposure is expected.

Transfer Coefficients: It is the policy of HED to use the best available data to assess postapplication exposure. Sources of generic post-application data, used as surrogate data in the 

absence of chemical-specific data, are derived from ARTF exposure monitoring studies, and, as 

proprietary data, are subject to the data protection provisions of FIFRA. The standard values 

recommended for use in predicting post-application exposure that are used in this assessment, 

known as “transfer coefficients”, are presented in the ExpoSAC Policy 312” which, along with 

additional information about the ARTF data, can be found at the Agency website13.

Table 6.2.2.1. Anticipated Post-Application Activities and Dermal Transfer Coefficients.

Crops

Policy Crop 

Group 

Category

Crop 

Height

Foliage 

Density

Transfer 

Coefficients 

(cm2/hr)

Activities

Golf Course Turf/sod Low Full 3700 Maintenance

Golf Course Turf/Sod Low Full 2500 Maintenance, greens only

Sod Turf/Sod Low Full 6700 Maintenance, Slab Harvesting, 

Transplanting/Planting

Sugarcane Sugarcane High Full 1100 Scouting

Sugarcane Sugarcane High Full 8800 Hand Harvesting

Sugarcane Sugarcane Low Minimum 70 Hand Weeding

Cereals (Wheat, 

Barley, Oats, 

Triticale)

Field/row 

crop, 

low/medium

Low Full/Minimum 1100 Scouting

Cereals (Wheat, 

Barley, Oats, 

Triticale)

Field/row 

crop, 

low/medium

Low Full/Minimum 70 Hand Weeding

Grasses Grown For 

Seed

Field/row 

crop, 

low/medium

Low Full 1900 Hand Set Irrigation

Grasses Grown For 

Seed

Field/row 

crop, 

low/medium

Low Minimum 1100 Scouting

Application Rate: The maximum application rates, as detailed in Table 4.1, were used in the 

occupational post-application calculations. 

Exposure Time: The average occupational workday is assumed to be 8 hours. 

Dislodgeable Foliar Residues: 

 

12 Available: http://www.epa.gov/pesticides/science/exposac_policy3.pdf

13 Available: http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 33 of 41

Chemical-specific dislodgeable foliar residue (DFR) data have not been submitted for 

trinexapac-ethyl. Therefore, the assessment uses HED’s default assumption that 25% of the 

application is available for transfer on day 0 following the application and the residues dissipate 

at a rate of 10% each following day.

Chemical-specific TTR data are available for trinexapac-ethyl and were used in the occupational 

post-application exposure assessment to assess turf in conjunction with standard default 

assumptions to assess sugarcane, cereals (wheat, barley, oats, triticale), and grasses grown for 

seed. Therefore, the assessment uses surface residues from the day of application (assume that 

individuals could be exposed to residues immediately after application) for occupational turf uses

(see Appendix B for more details). 

Occupational Post-application Non-Cancer Dermal Exposure and Risk Estimate Equations

The algorithms used to estimate non-cancer exposure and dose for occupational post-application 

workers can be found in Appendix A.

Occupational Post-application Non-Cancer Dermal Risk Estimates

The short- and intermediate-term occupational post-application dermal exposure and risk 

estimates indicate that the MOEs are not of concern to HED (i.e., MOEs ≥ 100) on the day of 

application, except for hand-harvesting sugarcane (MOE=87) where risk estimates are of concern 

until 2 days after application (MOE=110) as detailed in Table 6.2.2.2.

Table 6.2.2.2. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Trinexapacethyl.

Crop/Site Activities Transfer Coefficient 

(cm2/hr) DFR/TTR1 Dermal Dose (mg/kg/day)2 MOE3

Short-term/Intermediate-term

Granular Formulation

Golf Course (Turf/Sod) Maintenance 3700 0.015 0.005 12,000

Golf Course (Turf/Sod) Maintenance, Greens 

Only 2500 0.015 0.003 18,000

Liquid Formulations

Golf Course (Turf/Sod) Maintenance 3700 0.006 0.002 29,000

Golf Course (Turf/Sod) Maintenance, Greens 

Only 2500 0.006 0.001 43,000

Sod (Turf/Sod)

Maintenance, 

Harvesting, Slab, 

Transplanting

6700 0.012 0.008 8,000

Sugarcane Scouting 1100 0.87 0.086 700

Sugarcane Hand Harvesting 8800 0.87 0.688

87 (MOE=110 at 

Day 2 after 

treatment)

Sugarcane Hand Weeding 70 0.87 0.005 11,000

Cereals (Wheat, Barley, 

Oats, Triticale) Scouting 1100 0.31 0.030 2,000

Cereals (Wheat, Barley, 

Oats, Triticale) Hand Weeding 70 0.31 0.002 31,000
Page 34 of 41

Table 6.2.2.2. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Trinexapacethyl.

Crop/Site Activities Transfer Coefficient 

(cm2/hr) DFR/TTR1 Dermal Dose (mg/kg/day)2 MOE3

Short-term/Intermediate-term

Grasses Grown For 

Seed Hand Set Irrigation 1900 1.40 0.239 250

Grasses Grown For 

Seed Scouting 1100 1.40 0.139 430

1 DFR = Application Rate × F × (1-D)t × 4.54E8 μg/lb × 2.47E-8 acre/cm2; where F = 0.25 and D = 0.10 per day or TTR = chemical-specific 

data from MRID 45260201 for the Indiana site adjusted for differences in application rates

2 Daily Dermal Dose = [DFR (μg/cm2) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (77.5%)] BW (69 kg).

3 MOE = POD (60 mg/kg/day) / Daily Dermal Dose. Daily Dermal Dose = [DFR/TTR (μg/cm2) × TC × 0.001 mg/μg × 8 hrs/day × dermal 

absorption factor (77.5%)] BW (69 kg).

Restricted Entry Interval

The REI specified on the currently registered labels is based on the acute toxicity of trinexapac 

ethyl. Trinexapac-ethyl is classified as Toxicity Category III via the dermal route and Toxicity 

Category IV for skin irritation potential. It is not a skin sensitizer. Short- and intermediate-term 

post-application risk estimates were not a concern on day 0 (12 hours following application) for 

all post-application activities. Under 40 CFR 156.208 (c) (2) (iii), ai’s classified as Acute III or 

IV for acute dermal, eye irritation and primary skin irrigation are assigned a 12-hour REI. 

Therefore, the [156 subpart K] Worker Protection Statement interim REI of 12 hours is adequate 

to protect agricultural workers from post-application exposures to trinexapac-ethyl. 
Page 35 of 41

Appendix A. Summary of Occupational and Residential Non-cancer Algorithms

Residential Non-cancer Handler Algorithms

Daily dermal and inhalation exposure (mg/day) for residential pesticide handlers, for a given 

formulation-application method combination, is estimated by multiplying the formulationapplication method-specific unit exposure by an estimate of the amount of active ingredient 

handled in a day, using the equation below:

E = UE * AR * A

where:

E = exposure (mg/day);

UE = unit exposure (mg/lb ai);

AR = application rate (e.g., lb ai/ft2, lb ai/gal); and

A = area treated or amount handled (e.g., ft2/day, gal/day).

1.2 Residential Handler Dose Calculations

Dermal and/or inhalation absorbed doses normalized to body weight are calculated as:

D = E *AF / BW

where:

D = dose (mg/kg-day);

E = exposure (mg/day);

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

BW = body weight (kg).

Residential Non-cancer Post-application Algorithms

Post-application Dermal Exposure Algorithm – Physical Activities on Turf

Exposure resulting from contacting previously treated turf while performing physical activities is 

calculated as shown below. Residential post-application exposure assessment must include 

calculation of exposure on the day of application. Therefore, though an assessment can present 

exposures for any day “t” following the application, it must include “day 0” exposure.

E = TTRt * CF1 * TC * ET

where:

E = exposure (mg/day);

TTRt = turf transferable residue on day t (μg/cm2);

CF1 = weight unit conversion factor (0.001 mg/μg);
Page 36 of 41

TC = transfer coefficient (cm2/hr); and

ET = exposure time (hr/day).

Chemical-specific TTR data are available, 

Dermal absorbed doses are calculated as:

BW

E AF D*

where:

D = dose (mg/kg-day);

E = exposure (mg/day);

AF = absorption factor (dermal); and

BW = body weight (kg).

Table A-2: Turf (Physical Activities) -- Inputs for Residential Post-application Dermal Exposure

Algorithm Notation Exposure Factor

(units) Point Estimate(s)

TC

Transfer 

Coefficient 

(cm2/hr)

L/WP/WDG

Adults 180,000

Children 1 < 2 years old 49,000

Granules

Adults 200,000

Children 1 < 2 years old 54,000

ET Exposure Time

(hours per day)

Adults 1.5

Children 1 < 2 years old 1.5

BW Body Weight

(kg)

Adults 69

Children 1 < 2 years old 11

L/WP/WDG = Liquids/Wettable Powders/Water-dispersible Granules

Post-application Dermal Exposure Algorithm – Mowing

Exposure resulting from contacting previously treated turf while mowing is calculated as 

follows:

E = TTRt * CF1 * TC * ET

where:

E = exposure (mg/day);

TTRt = turf transferable residue on day "t" (μg/cm2);

CF1 = weight unit conversion factor (0.001 mg/μg);

TC = transfer coefficient (cm2/hr); and

ET = exposure time (hr/day).

and

TTRt = AR * FAR * (1-FD)

t

* CF2 * CF3
Page 37 of 41

where:

TTRt = turf transferable residue on day "t" (μg/cm2);

AR = application rate (lbs ai/ft2or lb ai/acre);

FAR = fraction of ai retained on turf (unitless);

FD = fraction of residue that dissipates daily (unitless);

t = post-application day on which exposure is being assessed;

CF2= weight unit conversion factor (4.54 x 108μg/lb); and

CF3 = area unit conversion factor (1.08 x 10-3ft2/cm2or 2.47 x 10-8acre/cm2).

Absorbed dose, normalized to body weight, are calculated as:

BW

E AF D*

where:

D = dose (mg/kg-day);

E = exposure (mg/day); 

AF = absorption factor (dermal); and

BW = body weight (kg).

Table A-6: Turf (Mowing) – Inputs for Residential Post-application Dermal Exposure 

Algorithm Notation Exposure Factor

(units) Point Estimate(s)

TC Transfer Coefficient

(cm2/hr)

Adult 5,500

Children 11 < 16 years 

old 4,500

ET Exposure time 

(hours per day) 1

BW Body Weight 

(kg)

Adults 69

Children 11 < 16 years 

old 57

L/WP/WDG = liquid/wettable powder/water dispersible granule

Post-application Dermal Exposure Algorithm – Golfing

Exposure resulting from contacting previously treated turf while golfing is calculated as follows:

E = TTRt * CF1 * TC * ET

where:

E = exposure (mg/day); 

TTRt = turf transferable residue on day "t" (μg/cm2);

CF1 = weight unit conversion factor (0.001 mg/μg);

TC = transfer coefficient (cm2/hr); and

ET = exposure time (hr/day).

and
Page 38 of 41

TTRt = AR * F * (1-FD)

t

* CF2 * CF3

where:

TTRt = turf transferable residue on day "t" (μg/cm2);

AR = application rate (lbs ai/ft2or lb ai/acre);

F = fraction of ai retained on turf (unitless);’

FD = fraction of residue that dissipates daily (unitless);

t = post-application day on which exposure is being assessed;

CF2 = weight unit conversion factor (4.54 x 108μg/lb); and

CF3 = area unit conversion factor (1.08 x 10-3ft2/cm2or 2.47 x 10-8acre/cm2).

Absorbed dose, normalized to body weight, is calculated as:

BW

E AF D*

where:

D = dose (mg/kg-day);

E = exposure (mg/day); 

AF = absorption factor (dermal); and

BW = body weight (kg).

Table A-7: Turf (Golfing) – Inputs for Residential Post-application Dermal Exposure 

Algorithm 

Notation

Exposure Factor

(units)

Point Estimate(s)

TC Transfer Coefficient

(cm2/hr)

Adult 5,300

Children 11 < 16 years old 4,400

Children 6 < 11 years old 2,900

ET Exposure time

(hours per day)

Pesticides used on greens, tees, 

and fairways 

4

Pesticides used only on greens 

and tees

1

BW Body Weight

(kg)

Adults 69

Children 11 < 16 years old 57

Children 6 < 11 years old 32

NA = not applicable

L/WP/WDG = liquid/wettable powder/water dispersible granule

Occupational Non-cancer Handler Algorithms

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

where:

E = exposure (mg ai/day),

UE = unit exposure (μg ai/lb ai),
Page 39 of 41

AR = maximum application rate according to registered labels (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:

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:

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).

Occupational Non-cancer Post-application Algorithms

Potential daily exposures for occupational post-application workers are calculated using the 

following formulas:

where:

DFRt = dislodgeable foliage residue on day "t" (μg/cm2),

AR = application rate (lb ai/acre),

F = fraction of ai retained on foliage or 25% (unitless),

D = fraction of residue that dissipates daily or 10% (unitless), and

t = number of days after application day (days).
Page 40 of 41

where:

E = exposure (mg ai/day),

TC = transfer coefficient (cm2/hr),

DFRt = dislodgeable foliar residue on day “t” (μg/cm2), and

ET = exposure time (hours/day).

The daily doses are calculated using the following formula:

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 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 dose received by occupational post-application workers is compared to the 

appropriate POD (i.e., NOAEL) to assess the risk to occupational post-application workers. All 

MOE values are calculated using the following formula:

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).
Page 41 of 41

Appendix B. Summary of the TTR Study: Determination of Transferable Residues of 

Trinexapac-ethyl Turf Treated with Primo Maxx (MRID 45260201)

The study was designed to determine the total transferable residues (TTR) of trinexapac-ethyl 

dislodged from turf treated with Primo Maxx, a microemulsion concentrate containing 11.3% 

trinexapac-ethyl as the active ingredient. The test site consisted of one treated plot located in 

Georgia, California, and Indiana. The treated plot was divided into subplots and three replicate 

samples were collected at each sampling interval. Applications were made at a rate of 0.69 lb 

ai/A to the treated plot (maximum application rate for edging/banding), which is twice the 

maximum broadcast application rate of 0.35 lb ai/A. The application was made as a ground 

application to a single treatment plot at each site using a water carrier through a turf handgun 

sprayer. The Modified California Roller technique was used to evaluate the amount of 

transferable residues from turf grass. First-order dissipation kinetics were assumed to generate 

dissipation curves for trinexapac-ethyl at the test sites. The individual residue data were

collected after the last application through the first day when all triplicate TTR levels were less 

than the level of quantitation (LOQ). For values that were less than the LOQ, a value was used 

that is one-half of the LOQ. A linear regression analysis was conducted using the natural 

logarithm of the individual TTR values from cloth dosimeters.

At the Indiana test site, the average trinexapac-ethyl TTR value on Day 0 was 0.054 ug/cm2. At 

the California test site, the average trinexapac-ethyl TTR value on Day 0 was 0.024 ug/cm2. At 

the Georgia test site, the average trinexapac-ethyl TTR value on Day 0 was 0.038 ug/cm2. The 

average TTR values were highest immediately after application for all sites.

Based on the study results, the half-life was determined to be 11.1 hours (R2=0.893) for Indiana, 

13.3 hours (R2=0.944) for California, and 7.6 hours (R2=0.984) for Georgia.

The results of the study are acceptable for risk assessment purposes.

Table B1. Summary of TTR Values and Regression Analysis Results for Treated Turf with Primo Maxx 

(MRID# 45260201).

Input/Parameter Georgia California Indiana

Application Rate (lb ai/A) 0.69 0.69 0.69

Spray Volume (GPA) 145 124.8 114

Measured Average Day 0 

Residue (μg/cm2)

0.038 0.024 0.054

Predicted Day 0 Residue 

(μg/cm2)

0.031 0.018 0.023

Slope -2.20 -1.25 -1.50

Half-life (days) 0.315 0.553 0.464

R

2

0.984 0.944 0.893