Page 3 of 23

1.0 Executive Summary

HED has conducted an occupational and residential exposure assessment for the proposed use of 

the herbicide ai, topramezone, on golf courses, sod farms and residential turfgrass. Topramezone 

is currently registered for use on field, pop, seed and sweet corn, as well as non-crop 

ornamentals, rights-of-way, tree plantations, and other non-crop areas. There are currently no 

registered residential uses.

The proposed label allows for broadcast applications to golf courses and sod farms, but restricts 

applications to residential turfgrass and athletic fields to spot spray only. The end-use product is 

Topramezone 2.8 SC (EPA Reg # 7969-xxx), a 2.8 lb ai/gallon liquid formulation. The 

maximum single application rate proposed is 2 fl oz/A (0.044 lb ai/A) or 0.001 lb ai/1000 ft2

(with a spray volume of 1 gallon per 1000 ft2). 

Topramezone is a 4-hydroxyphenylpyruvate dioxygenase (HHPD) inhibitor and the effects 

observed following repeated oral exposures to topramezone are consistent with those expected 

from HPPD inhibition in mammals. The primary target organs affected following topramezone 

administration were the eyes, thyroid, and pancreas. Points of departure (PODs) for the dermal, 

inhalation, and incidental oral routes are based on effects seen in a two generation reproduction

study with a no-observed-adverse-effect level (NOAEL) of 0.4 mg/kg/day. Since an oral study 

was selected for the short- and intermediate-term assessments, a 2.6% dermal absorption factor 

was applied and inhalation toxicity was assumed to be equivalent to oral toxicity. Exposures 

from the dermal and inhalation routes were combined because the PODs for these routes are 

based on the same toxicological effects. HED’s level of concern (LOC) for topramezone

occupational and residential dermal, inhalation and incidental oral exposures is 100 (i.e., a 

margin of exposure (MOE) less than 100 is considered by HED to be a risk of concern). The 

LOC is based on 10X to account for interspecies extrapolation to humans from the animal test 

species and 10X to account for intraspecies sensitivity. 

The residential handler assessment was completed assuming the maximum label application rate 

allowed for residential turfgrass and athletic fields. The proposed label only allows for spot 

applications to residential sites; therefore, it was assumed that handheld equipment would be 

used. The label states to use “low-pressure sprayers”; therefore, backpack and manuallypressurized handwands were assessed for residential handlers. Dermal and incidental oral 

exposure scenarios were assessed for potential post-application exposure from the use of 

topramezone. A chemical-specific turf transferable residue (TTR) study was available and was 

used to estimate transferable residues from treated turf. Residential exposure scenarios are 

considered to be short-term only, due to the infrequent use patterns associated with homeowner 

products. 

Residential handler dermal and inhalation risk estimates were calculated. For residential

handlers, dermal and inhalation MOEs above 100 do not exceed HED’s LOC. The combined 

dermal and inhalation exposure risks for mixer/loaders are not of concern (i.e., MOEs >100) at 

baseline for all scenarios. Residential dermal and incidental oral post-application risk estimates 

were also calculated. The combined MOEs are greater than 100 and are not of concern.
Page 4 of 23

The occupational handler assessment was completed assuming the maximum label application 

rate. The proposed label allows for application by groundboom or by handheld equipment. 

Based on the activity use pattern, the duration of exposure is expected to be short- term (ST; 1 to 

30 days) and intermediate- term (IT; 1 to 6 months) for occupational scenarios; long-term 

exposures (greater than 6 months) are not anticipated based on the proposed use pattern. The 

same endpoints are used for short- and intermediate-term exposures; therefore, risks are the same 

for all durations of exposure. The proposed label requires long-sleeved shirt and long pants, 

chemical-resistant gloves, shoes plus socks and goggles, face shield or safety glasses as dermal 

personal protective equipment (PPE) for all applicators and other handlers. 

Occupational handler dermal and inhalation risk estimates were calculated. For occupational 

handlers, dermal and inhalation MOEs above 100 do not exceed HED’s LOC. The combined 

dermal and inhalation estimated risks are not of concern (i.e., MOEs >100) at baseline for all 

scenarios. Occupational dermal post-application risk estimates were calculated. The resulting 

MOEs are greater than 100 on day 0 (12 hours after application) for all activities. Since the postapplication MOEs are not of concern, the restricted entry interval (REI) for topramezone is based 

on the acute toxicity categories. Topramezone has low acute toxicity via the oral, dermal and 

inhalation routes of exposure (Toxicity category III or IV). It is a slight eye and dermal irritant 

(Toxicity category III and IV), but is not a dermal sensitizer. Therefore, the Worker Protection 

Standard (WPS) interim REI of 12 hours is adequate to protect agricultural workers from postapplication exposures to topramezone. 

Review of Human Research

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 

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 Agricultural Re-entry Task Force (ARTF) database are subject to 

ethics review pursuant to 40 CFR 26, have received that review, and are compliant with 

applicable ethics requirements. For certain studies that 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 http://www.epa.gov/pesticides/science/handler-exposure-data.html and 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html.

2.0 Hazard Profile

Topramezone has low acute toxicity via the oral, dermal and inhalation routes of exposure 

(Toxicity category III or IV). It is a slight eye and dermal irritant (Toxicity category III and IV), 

but is not a dermal sensitizer. Table 2.0.1 presents a summary of the acute toxicity information 

for topramezone.

Table 2.0.1. Acute Toxicity Profile on Topramezone.

OPPTS Guideline Study Type Results Toxicity Category

870.1100 Acute oral toxicity / rat LD50 2000 mg/kg (males and females) III

870.1200 Acute dermal toxicity / rat LD50 2000 mg/kg (males and females) III
Page 5 of 23

Table 2.0.1. Acute Toxicity Profile on Topramezone.

OPPTS Guideline Study Type Results Toxicity Category

870.1300 Acute inhalation toxicity / 

rat LC50 5.05 mg/L (males and females) IV

870.2400 Primary eye irritation / 

rabbit Slight irritant III

870.2500 Primary dermal irritation / 

rabbit Slight irritant IV

870.2600 Dermal sensitization / 

guinea pig Non-Sensitizer --

The effects observed following repeated oral exposures to topramezone are consistent with those 

expected from HPPD inhibition in mammals. The primary target organs affected following 

topramezone administration were the eyes, thyroid, and pancreas. The most sensitive species 

was the rat and, at least in rats and dogs, males were more sensitive than females. The Cancer 

Assessment Review Committee (CARC) classified topramezone as “Not likely to be 

carcinogenic to humans at doses that do not alter rat thyroid hormone homeostasis.” The CARC 

determined that quantification of human cancer risk is not required since the NOAEL (0.4 

mg/kg/day) for non-cancer risk assessment is not expected to alter thyroid hormone homeostasis 

nor result in thyroid tumor formation. 

The short- (1-30 days), and intermediate- (1-6 months) term dermal, inhalation and incidental 

oral toxicological PODs were identified from a two generation reproduction study where the 

effects were based on decreased body weight, body-weight gain in males, increased thyroid and 

kidney weights of both sexes, and microscopic findings in eyes, kidney and thyroid of both 

sexes. The NOAEL was 0.4 mg/kg/day. Since an oral study was used, a dermal absorption 

factor of 2.6% was used for the dermal risk assessment. Inhalation toxicity is assumed to be 

equivalent to oral toxicity. A summary of the toxicological endpoints and doses chosen for the

relevant exposure scenarios for human risk assessment are found in Table 2.0.2.

Table 2.0.2: Summary of Toxicology Endpoints and Point of Departure Doses for Topramezone in Dietary and 

Residential Risk Assessment.

Exposure

Scenario

Point of Departure Uncertainty/ FQPA 

Safety Factors or LOC 

for Risk Assessment

Study and Toxicological Effects

Incidental Oral

(Short- and 

Intermediate-Term)

NOAEL = 0.4 

mg/kg/day

Residential LOC for 

MOE = 100

Two Generation Reproduction Study in Rats

Offspring LOAEL = 4.2 mg/kg/day based 

decreases in body weights and body-weight 

gains in the F2 generation offspring and 

increased time to preputial separation in the F1 

male offspring

Short- and 

Intermediate-Term, 

Dermal 

Oral NOAEL= 0.4 

mg/kg/day

(dermal-absorption

factor = 2.6%)

Residential LOC for 

MOE = 100

Two Generation Reproduction Study in Rats

Parental LOAEL = 4.2 mg/kg/day based on 

decreased body weight, body-weight gain in 

males, increased thyroid and kidney weights of 

both sexes, and microscopic findings in eyes, 

kidney and thyroid of both sexes.

Short- and 

Intermediate-Term 

Oral NOAEL= 0.4 

mg/kg/day

Residential LOC for 

MOE = 100

Two Generation Reproduction Study in Rats
Page 6 of 23

Table 2.0.2: Summary of Toxicology Endpoints and Point of Departure Doses for Topramezone in Dietary and 

Residential Risk Assessment.

Exposure

Scenario

Point of Departure Uncertainty/ FQPA 

Safety Factors or LOC 

for Risk Assessment

Study and Toxicological Effects

Inhalation

(inhalation absorption 

rate = 100%)

Parental LOAEL = 4.2 mg/kg/day based on 

decreased body weight, body-weight gain in 

males, increased thyroid and kidney weights of 

both sexes, and microscopic findings in eyes, 

kidney and thyroid of both sexes.

Cancer 

(Oral, dermal, 

inhalation)

In accordance with the EPA Final Guidelines for Carcinogen Risk Assessment (March 29, 2005), the CARC classified 

topramezone as “Not likely to be carcinogenic to humans at doses that do not alter rat thyroid hormone homeostasis”. The 

CARC determined that the thyroid tumors arise through a non-linear mode of action and the NOAEL (0.4 mg/kg/day) 

established for deriving the chronic Reference Dose (cRfD) is not expected to alter thyroid hormone homeostasis nor result in

thyroid tumor formation. 

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 (intraspecies). UFH = 

potential variation in sensitivity among members of the human population (interspecies). FQPA SF = FQPA Safety Factor. MOE = margin of 

exposure. LOC = level of concern. 

The Agency’s level of concern for risks (i.e., target level for MOEs) is defined by the uncertainty 

factors that are applied to the assessment. 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 has concluded that the FQPA safety factor for 

topramezone can be reduced to 1X for residential non-dietary scenarios. The total uncertainty 

factor that has been applied to occupational and residential risk assessments is 100 for short- and 

intermediate-term dermal, inhalation and incidental oral exposures. 

3.0 Use Profile

Topramezone 2.8 SC (EPA Reg # 7969-xxx) is a 29.7% (2.8 lb ai/gal) liquid formulation

proposed for use on golf courses, sod farms and residential turfgrass. The specific use sites listed 

on the label include: airports, athletic fields, cemeteries, golf courses, grounds or lawns around 

residential and commercial establishments, houses of worship, military and other institutions, 

single/multifamily dwellings, parks, picnic grounds, roadsides, schools, and sod farms. 

The label allows for broadcast applications via ground equipment to golf courses and sod farms. 

Applications to residential sites are limited to spot sprays using low-pressure equipment, such as 

backpack and manually-pressurized sprayers. The label prohibits application to golf course 

collars or greens, and application via chemigation or air. The REI specified on the label is 12 

hours. The use profile proposed for this Section 3 registration is summarized in Table 3.0.1.
Page 7 of 23

Table 3.0.1. Summary of Directions for Use of Topramezone.

Application 

Equipmenta

Formulation 

[EPA Reg. 

No.]

Maximum 

Application 

Rate

Max. No. 

Applic. 

per Year

Maximum 

Yearly 

Application 

Rate

(lb ai/A)

Use Directions and Limitations

Golf Courses, Sod Farms, Residential Turfgrass

Groundboom 

applications

Soluble 

concentrate

[7969-xxx]

0.044 lb ai/A

2 0.089

REI = 12 hrs

Application to residential turfgrass and 

athletic fields limited to spot sprays 

(i.e., handheld equipment)

Do not apply to golf course collars or 

greens

Do not apply via chemigation or air

If single application of topramezone 

does not provide complete control, a 

sequential application can be made 2 to 

3 weeks later

Handheld 

equipment:

(1) Backpack

(2) Manuallypressurized 

handwand

(3) 

Mechanicallypressurized 

handgun

0.001 lb 

ai/1000 ft2

(spray 

volume: 1 

gallon/1000 

ft2)

a. Proposed label personal protective equipment: Applicators and all handlers must wear long-sleeved shirt and long pants, chemical-resistant 

gloves, shoes plus socks, goggles, face shield or safety glasses.

4.0 Occupational Exposure/Risk Characterization

4.1 Short- and Intermediate-Term Handler Risk

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 proposed uses. 

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

following scenarios: 

(1) Open mixing/loading liquids for groundboom applications;

(2) Applying sprays via groundboom applications;

(3) Mixing/loading/applying with a manually-pressurized handwand; 

(4) Mixing/loading/applying with a mechanically-pressurized handwand; and

(5) Mixing/loading/applying with a backpack sprayer.

For pesticide handlers, HED presents estimates of dermal exposure for “baseline” (i.e., workers 

wearing a single layer of work clothing consisting of a long sleeved shirt, long pants, shoes plus 

socks and no protective gloves), as well as for “baseline” and the use of protective gloves or 

other PPE, as might be necessary. The topramezone product labels direct mixers, loaders, 

applicators and other handlers to wear long-sleeved shirt and long pants, chemical-resistant 

gloves, shoes plus socks, goggles, face shield or safety glasses.

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 the 
Page 8 of 23

PHED 1.1, the AHETF database, the ORETF database, or other registrant-submitted 

occupational exposure studies. Some of these data are proprietary 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 Table” 

(http://www.epa.gov/opp00001/science/handler-exposure-table.pdf), which, along with 

additional information on HED policy on use of surrogate data, including descriptions of the 

various sources, can be found at http://www.epa.gov/pesticides/science/handler-exposuredata.html.

 

Typically, HED completes short- and intermediate-term assessments for occupational scenarios 

in all cases because these kinds of exposures are likely and acceptable use/usage data are not 

available to justify deleting intermediate-term scenarios. Based on use data and label 

instructions, HED believes that occupational exposures may occur over a single day or up to 

weeks at a time for many of the use-patterns and that intermittent exposure over several weeks 

may also occur. Some applicators may apply these products over a period of weeks, because 

they are commercial applicators who are completing multiple pesticide applications for multiple 

clients. Long-term exposures are not expected; therefore, a long-term assessment was not 

conducted. 

The daily areas treated and amounts handled were defined for each handler scenario (in 

appropriate units) by determining the amount that can be reasonably treated by an individual in a 

single day. When possible, the assumptions for daily areas treated and amounts handled are 

taken from the HED’s ExpoSAC Policy #9: “Standard Values for Daily Acres Treated in 

Agriculture”, which was revised on July 5, 2000. Values used for area treated and amount 

handled in each scenario include: 80 acres for groundboom application, 1000 gallons for 

mechanically-pressurized handgun, and 40 gallons for backpack and manually-pressurized 

handwand equipment.

Since an oral study was selected for the short- and intermediate-term assessments, a 2.6% dermal 

absorption factor was applied. In addition, an assumption of equivalent toxicity from the oral 

and inhalation routes of exposure was made. A body weight of 80 kg was used. Daily dermal or 

inhalation handler exposures are estimated for each applicable handler task with the application 

rate, the amount handled or area treated in a day, and the applicable dermal or inhalation unit 

exposure using the following formula:

Daily Exposure = Unit Exposure x Application Rate x Daily Area Treated

Where: 

Daily Exposure = Amount (mg/day) deposited on the surface of the skin that is available for 

dermal absorption or amount inhaled that is available for inhalation absorption;

Unit Exposure = Unit exposure value (mg/lb ai) derived from August 1998 PHED data;

Application Rate = Normalized application rate based on a logical unit treatment, such as acres (A); 

and

Daily Area Treated = Normalized application area based on a logical unit treatment such as acres 

(A/day). 
Page 9 of 23

The daily dermal or inhalation dose is calculated by normalizing the daily exposure by body 

weight and adjusting, if necessary, with an appropriate dermal or inhalation absorption factor 

using the following formula:

Average Daily Dose = Daily Exposure x Absorption Factor / Body Weight

Where:

Average Daily Dose = Absorbed dose received from exposure to a pesticide in a given scenario 

(mg/kg/day);

Daily Exposure = Amount (mg/day) deposited on the surface of the skin that is available for 

dermal absorption or amount inhaled that is available for inhalation absorption;

Absorption Factor = A measure of the amount of chemical that crosses a biological boundary such as 

the skin or lungs (% of the total available absorbed); and

Body Weight = Body weight determined to represent the population of interest in a risk 

assessment (kg).

Dermal and inhalation risks were combined in this assessment, since the toxicological effects for 

these exposure routes were similar. Dermal and inhalation risks were combined using the 

following formula:

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

Table 4.1.1 presents the exposure/risks for short and intermediate-term dermal and inhalation 

exposures at baseline. The combined dermal and inhalation exposure risk estimates are not of 

concern (i.e., MOEs >100) at baseline for all scenarios.
Page 10 of 23

Table 4.1.1. Short-/Intermediate-Term Occupational Exposure and Risk Estimates for Topramezone. 

All estimates are at Baseline (i.e., no gloves/respirator).

Exposure Scenario Crop or 

Target

Dermal Unit 

Exposure

(ug/lb ai)1

Inhalation 

Unit 

Exposure

(ug/lb ai)1

Application 

Rate2

Amount 

Treated 

Daily3

Dermal Inhalation Total

Baseline Baseline Dose

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

Mixer/Loader

Mixing/Loading Liquids 

for Groundboom 

Applications

Turf 220 0.219 0.044 lb 

ai/A 80 A 0.00025 1,600 9.6 x 10-6

42,000 1,500

Applicator

Applying Sprays via 

Groundboom Equipment Turf 78.6 0.34 0.044 lb ai/A 80 A 0.00009 4,400 1.5 x 10-5

27,000 3,800

Mixer/Loader/Applicator

Mixing/Loading/Applying 

Liquids via Manuallypressurized HandwandTurf 100,000 30 0.001 lb 

ai/gallon

40 

gallons 0.0013 310 1.5 x 10-5

27,000 300

Mixing/Loading/Applying 

Liquids via Backpack 

Sprayer

Turf 8,260 2.58 0.001 lb 

ai/gallon

40 

gallons 0.00011 3,700 1.3 x 10-6

310,000 3,700

Mixing/Loading/Applying 

Liquids via Mechicallypressurized HandgunTurf 1,140 1.9 0.001 lb 

ai/gallon

1000 

gallons 0.00037 1,100 2.4 x 10-5

17,000 1,000

1 Based on “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (September 26, 2011); includes data from PHED/ORETF/AHETF (level of mitigation: Baseline and PPE 

(gloves)).

2 Based on proposed label (Reg. No. #7969-xxx).

3 Exposure Science Advisory Council Policy #9.1.

4 Dermal Dose = Dermal Unit Exposure (mg/lb ai) x Application Rate (lb ai/acre or lb ai/gallon) x Area Treated or Amount Handled (A/day or Gallons/day) x DAF (2.6%)/BW (80 kg).

5 Dermal MOE = Dermal NOAEL (0.4 mg/kg/day)/Dermal Dose (mg/kg/day).

6 Inhalation Dose = Inhalation Unit Exposure (mg/kg) x Application Rate (lb ai/acre or lb ai/gallon) x Area Treated or Amount Handled (A/day or Gallons/day) /BW (80 kg).

7 Inhalation MOE = Inhalation NOAEL (0.4 mg/kg/day)/ Inhalation Dose (mg/kg/day).

8 Total MOE = NOAEL (mg/kg/day)/Dermal Dose + Inhalation Dose.
Page 11 of 23

4.2 Short- and Intermediate-Term Post-Application Risk

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. 

4.2.1 Dermal Post-Application Risk

In the case of topramezone, there is a potential for post-application dermal exposure to workers 

following foliar applications of topramezone to golf courses and sod farms. It is the policy of 

HED to use the best available data to assess post-application exposure. Sources of generic postapplication data, used as surrogate data in the absence of chemical-specific data, are derived 

from Agricultural Reentry Task Force (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 “Science Advisory Council for Exposure 

(ExpoSAC) Policy 3” (http://www.epa.gov/pesticides/science/exposac_policy3.pdf), which, 

along with additional information about the ARTF data, can be found at 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html. Table 4.2.1.1 provides a 

summary of the transfer coefficients and activities associated with golf course and sod farm turf.

Table 4.2.1.1. Post-application Activities and Dermal Transfer Coefficients.

Proposed Use Site Transfer Coefficients (cm2/hr) Activities

Turf

3,700 golf course maintenance

6,700 harvesting, maintenance, transplanting

In addition, the following assumptions and data were used in the topramezone dermal postapplication assessment:

• Application Rate = 0.044 lb ai/A 

• Exposure Duration = 8 hours per day

• Body Weight = 80 kg

• Dermal absorption = 2.6%

• Chemical-specific TTR data submitted in support of the proposed turf uses (MRID 

48379401).

Summary of the TTR Study: Determination of Transferable Residues of Topramezone 

Turf Treated with BAS 670 01 H (MRID 48379401)

This study was designed to determine the transferable turf residue (TTR) of topramezone 

dislodged from turf at three field trial sites in Pennsylvania, California, and Washington. Three 

separate plots were set up at each study site: (1) Plot #1 acted as a control plot, (2) Plot #2 
Page 12 of 23

received 3 applications for an average total application rate of 0.088 lb ai/A and (3) Plot #3 

received 1 application for an average total application rate of 0.046 lb ai/A. The re-treatment 

interval for Plot #2 at each site was approximately 21 days. Applications were made with 

groundboom equipment at the Washington and California sites and with a backpack sprayer 

equipped with a 3-gallon stainless tank and a hand-held boom at the Pennsylvania site. 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 topramezone. 

The individual data points (rather than averages) were included in the analysis for each site from 

the day of application up until the point where residues were less than the level of quantitation 

(LOQ). A separate analysis was performed for each site as well as a combined analysis of all the 

sites for the two different application regimes (plot #2 versus plot #3). 

For the plots that received 3 applications (plot #2 from each site), the highest average measured 

TTR values were 0.0015 μg/cm2(occurring immediately after the 2nd application), 0.0011 

μg/cm2(occurring 4 hours after the 3rd application), and 0.0011 μg/cm2(occurring immediately 

after the 2nd application) for the PA, WA, and CA sites, respectively. At all sites, residue levels 

declined to <LOQ by day 4 or 5 after the last application.

For plots that received 1 application (plot #3 from each site), the highest average measured TTR 

values were 0.0018 μg/cm2(occurring immediately after the application), 0.0016 μg/cm2

(occurring 4 hours after the application), and 0.0014 μg/cm2(occurring immediately after the 

application) for the PA, WA, and CA sites, respectively. At all sites, residue levels declined to 

<LOQ by day 4 or 5 after the application.

Based on the results from the plots that received 3 applications (plot #2 from each site), the halflife of topramezone on turf was determined to be 1.16 days (R2

=0.929), 1.43 days (R2=0.930), 

and 0.947 days (R2=0.932) for the PA, WA, and CA test sites, respectively. When the data were 

combined for the three sites for plot #2, the half-life of topramezone on turf was determined to be 

1.14 days (R2=0.899). Based on the results from the plots that received 1 application (plot #3 

from each site), the half-life of topramezone on turf was determined to be 1.06 days (R2=0.787), 

0.855 days (R2=0.864), and 0.874 days (R2=0.953) for the PA, WA, and CA test sites, 

respectively. When the data were combined for the three sites for plot #3, the half-life of 

topramezone on turf was determined to be 0.899 days (R2=0.865).

There were some quality control issues noted with regard to the field fortification samples and 

recoveries. Average field fortification recoveries were not in the acceptable range of 70 to 

120%. Individual recoveries ranged from 40 to 87% and average recoveries ranged from 49 to 

73%. In addition, the field fortification levels did not bracket the topramezone TTR values 

found on cloth dosimeters. The field fortification levels were 25 and 250 μg/sample. Field 

sample TTRs were all lower than the lowest field fortification level. Field sample TTRs ranged 

from 1.14 to 6.70 μg/sample. Fortified samples were analyzed; however, at levels close to the 

field samples during the method validation procedure. Method validation was performed prior to 

the start of the study and included an analysis of five replicates fortified with topramezone at the 

method LOQ (1 μg/sample) and five replicates fortified at a higher level (250 μg/sample). 
Page 13 of 23

Recoveries ranged from 67 to 87%, with an overall average recovery of 80%. Concurrent 

laboratory recoveries of topramezone ranged from 67 to 115%, averaging 88% (n=46). In 

addition, a freezer storage stability study was performed, where fortified cloth storage stability 

samples spiked at 25 μg/sample were analyzed after 45, 90 and 176 days of frozen storage. 

Recoveries ranged from 72 to 96% (n=6). 

Even though the field fortification recoveries were not all within the acceptable range outlined in 

the study guidelines, taking into consideration all of the quality control information provided, the 

results of this study are still considered acceptable for risk assessment purposes. 

Summary of TTR Values and Regression Analysis Results for Turf Treated with 3 Applications of Topramezone

(MRID# 48379401).

Input/Parameter Pennsylvania Washington California Combined

Application Rate 

(lb ai/A) 

Application 

Equipment

Average single application: 0.029 

Total rate: 0.088 

Backpack sprayer equipped with 

a 3-gallon stainless tank and a 

hand-held boom

Average single 

application: 0.030

Total rate: 0.090

Groundboom

Average single 

application rate: 0.029

Total rate: 0.087

Groundboom

Spray volume 

(GPA) 86.0 to 88.9 86.0 to 88.9 86.0 to 88.9

Measured Average 

Day 0 Residue 

(μg/cm2)

0.0007

(first application)

0.0015 

(second application)

0.0012

(third application)

0.0010

(first application)

0.0008

(second application)

0.0010

(third application)

0.0007

(first application)

0.0011

(second application)

0.0009

(third application)

0.0010

(third 

application)

Predicted Day 0 

Residue (μg/cm2)

a 0.0011 0.0012 0.0009 0.0011

Slope -0.599 -0.484 -0.732 -0.607

Half-life (days) 1.16 1.43 0.947 1.14

R

2

0.929 0.930 0.936 0.899

a. Regression data is based on TTRs collected after the third (last) application.

Summary of TTR Values and Regression Analysis Results for Turf Treated with 1 Application of Topramezone

(MRID# 48379401).

Input/Parameter Pennsylvania Washington California Combined

Application Rate 

(lb ai/A) 

Application 

Equipment

Total rate: 0.047

Backpack sprayer 

equipped with a 3-

gallon stainless tank 

and a hand-held boom

Total rate: 0.045

Groundboom

Total rate: 0.045

Groundboom

Spray volume (GPA) 85.1 to 89.0 85.1 to 89.0 85.1 to 89.0

Measured Average 

Day 0 (μg/cm2)

0.0018 0.0013 0.0014 0.0015

Predicted Day 0 

(μg/cm2)

0.0020 0.0020 0.0015 0.0019

Slope -0.654 -0.811 -0.793 -0.771

Half-life (days) 1.06 0.855 0.874 0.899

R

2

0.787 0.864 0.953 0.865
Page 14 of 23

The proposed use profile allows for a maximum of two applications, with the second application 

occurring 2 to 3 weeks after the first (if needed). Since this use pattern does not match either of 

the two approaches used in the study, the predicted TTR value on Day 0 based on the combined 

data from the plots from each site that received one application was chosen (0.0019 ug/cm2). 

This value is the highest TTR value reported for the study and is considered health protective for 

the proposed use.

The following equations were used to calculate risks for workers performing post-application 

activities:

Dermal Daily Doset = [TTRt (μg/cm2) x 0.001 mg/μg x TC (cm2/hr) x ET (hrs) x DAF]/BW (kg)

Where:

t = number of days after application day (days);

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

TC = transfer coefficient (cm2/hr);

ET = exposure time (hr/day); and,

BW = body weight (kg).

MOE= Dermal NOAEL (mg/kg/day)/Dermal Daily Dose (mg/kg/day)

Post-application dermal exposure and risk estimates for workers conducting activities on golf 

courses and sod farms resulted in MOEs greater than the LOC of 100 and, therefore, are not of 

concern. A summary of the post-application exposure and risk estimates from use of 

topramezone is provided in Table 4.1.2.2.

Table 4.1.2.2. Summary of Short-and Intermediate-term Occupational/Commercial Post-application Risks for 

Topramezone.

Crop/Site Activities

Transfer 

Coefficient 

(cm2/hr)

Application 

Rate 

(lb ai/A)

TTR1

(ug/cm2)

Day 0 

MOE2

Day X at 

which 

MOE ≥ 

LOC

Turf

golf course maintenance 3,700

0.044 0.0019

23,000 0

harvesting, maintenance, 

transplanting 6,700 13,000 0

1. TTR value is from chemical-specific turf transferable residue study (MRID 48379401)

2. MOE = POD (NOAEL, 0.4 mg/kg/day) / Daily Dermal Dose. Daily Dermal Dose = [TTR (μg/cm2) x TC x 0.001 mg/μg x 8 hrs/day x 2.6% 

dermal absorption] body weight (80 kg adult). 

REI

Short- and intermediate-term post-application risks were not a concern on day 0 (12 hours 

following application) for all post-application activities. Therefore, the REI is based on the acute 

toxicity of topramezone. Topramezone has low acute toxicity via the oral, dermal and inhalation 

routes of exposure (Toxicity category III or IV). It is a slight eye and dermal irritant (Toxicity 

category III and IV), but is not a dermal sensitizer. Therefore, the WPS interim REI of 12 hours 

is adequate to protect agricultural workers from post-application exposures to topramezone. 
Page 15 of 23

4.2.2 Inhalation Post-Application Risk

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

exposure assessment was not performed for topramezone at this time. However, there are 

multiple potential sources of post-application inhalation exposure to individuals performing postapplication 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. 

The Agency received the SAP’s final report on March 2, 2010 

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

process of evaluating the SAP report as well as available post-application inhalation exposure 

data generated by the Agricultural Reentry Task Force 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 topramezone. 

5.0 Residential (Non-Occupational) Exposure/Risk Characterization

Since the product can be applied to residential turf sites, exposure and risk estimates were 

calculated for both residential handlers and for post-application activities associated with 

residential turfgrass and golf courses. 

5.1 Residential Handler Exposure and Risk 

The residential handler exposure assessment estimates dermal and inhalation exposures for 

individuals using topramezone on residential turfgrass. The following are key differences 

between residential and occupational handler assessments: 

Residential handler exposure scenarios are considered to be short-term only, due to the 

infrequent use patterns associated with homeowner products.

A tiered approach for personal protection using increasing levels of PPE is not used in 

residential handler risk assessments. Homeowner handler assessments are based on the 

assumption that individuals are wearing shorts, short-sleeved shirts, socks, and shoes.

Homeowner handlers are expected to complete all tasks associated with the use of a 

pesticide product including mixing/loading if needed as well as the application.

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

following scenarios: 

(1) Mixing/Loading/Applying Liquids with Backpack Sprayer, and

(2) Mixing/Loading/Applying Liquids with Manually-pressurized Handwand.
Page 16 of 23

Unit exposure values and estimates for area treated were taken from the Health Effects 

Division’s 2012 Standard Operating Procedures for Residential Pesticide Exposure Assessment: 

Lawns/Turf. 

Handler dermal and/or inhalation exposures are estimated by multiplying the application 

method-specific unit exposure by an estimate of the amount of active ingredient handled in a 

day, using the following algorithm:

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).

Dermal and/or inhalation doses are estimated using the following algorithm:

BW

E*AF D

where:

D = dose rate (mg/kg-day);

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

BW = body weight (kg).

Dermal and inhalation risks were combined in this assessment, since the toxicological effects for 

these exposure routes were similar. Dermal and inhalation risks were combined using the 

following formula:

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

Short-term risks for residential handlers are presented in Table 5.1.1. Intermediate-term 

exposures are not likely because of the intermittent nature of applications by homeowners. 

Short-term combined dermal plus inhalation risk estimates to residential handlers do not exceed 

HED’s level of concern for all scenarios. 

Table 5.1.1. Residential Handler Exposure and Risk Estimates for Topramezone Applications to Turfgrass.

Exposure Scenario

Application 

Rate (lb 

ai/gallon)

a

Area 

Treated 

Daily 

(gallons)

b

Baseline Unit 

Exposuresb(mg/lb ai)

Baseline Dosed

(mg/kg/day) Baseline MOEe Combined MOEf

DermalcInhalationc Dermal Inhalation Dermal Inhalation Dermal + Inhalation 

Mixer/Loader/Applicator

Mixing/Loading/Applying 

Liquids with Manuallypressurized Handwand 0.001 5 63 0.018 0.0001 1.1 x 10-63,900 360,000 3,900
Page 17 of 23

Table 5.1.1. Residential Handler Exposure and Risk Estimates for Topramezone Applications to Turfgrass.

Exposure Scenario

Application 

Rate (lb 

ai/gallon)

a

Area 

Treated 

Daily 

(gallons)

b

Baseline Unit 

Exposuresb(mg/lb ai)

Baseline Dosed

(mg/kg/day) Baseline MOEe Combined MOEf

DermalcInhalationc Dermal Inhalation Dermal Inhalation Dermal + Inhalation 

Mixing/Loading/Applying 

Liquids with Backpack 

Sprayer

0.001 5 130 0.14 0.00021 8.8 x 10-61,900 46,000 1,800

a. Application rates based on proposed label for topramezone (Topramezone 2.8 SC, EPA Reg#7969-xxx).

b. Based on HED’s Standard Operating Procedures for Residential Pesticide Exposure Assessment; Lawns/Turf (January 2012).

c. Baseline Dermal: Long-sleeve shirt, long pants, and no gloves; Baseline Inhalation: no respirator. 

d. Dose (mg/kg/day) = daily unit exposure (mg/lb ai) x application rate (lb ai/gal) x gal treated * absorption factor (dermal = 2.6%) / body 

weight (80 kg).

e. MOE = NOAEL (0.4 mg/kg/day) / daily dose (mg/kg/day). Level of concern = 100.

f. Combined MOE = NOAEL (0.4 mg/kg/day) / combined dermal + inhalation dose (mg/kg/day).

5.2 Residential Post-application Exposure and Risk

Topramezone can be used in many areas that can be frequented by the general population 

including residential areas (e.g., home lawns). As a result, individuals can be exposed by 

entering these areas if they have been previously treated. 

5.2.1 Post-application Inhalation

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

assessment was not performed for topramezone at this time. However, volatilization of 

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

to pesticide applications. The Agency sought expert advice and input on issues related to 

volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 

Scientific Advisory Panel (SAP) in December 2009. The Agency received the SAP’s final report 

on March 2, 2010 (http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). The 

Agency is in the process of evaluating the SAP report and may, as appropriate, developing 

policies and procedures, to identifying 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 put into place, the Agency may revisit the need for a quantitative post-application 

inhalation exposure assessment for topramezone.

5.2.2 Post-application Dermal and Incidental Oral

Short-term dermal and incidental oral exposure and risk estimates have been assessed here and 

since the short- and intermediate-term PODs are the same, the short-term assessment is 

protective of longer-term exposures. However, in the case of incidental soil ingestion, HED has 

conducted a conservative assessment of potential intermediate-term oral risk from soil ingestion 

by using a yearly application rate of 0.089 lb ai/A, instead of the maximum single rate of 0.044 

lb ai/A, to address the persistence [half life of ≥ 240 days (J. Hetrick, D388368, 11/14/2011)] and 

likely potential build-up of topramezone in the soil. 

The scenarios, routes of exposure and lifestages assessed include:

Physical activities on turf: adults (dermal) and children 1 < 2 years old (dermal and 
Page 18 of 23

incidental oral);

Mowing: adults (dermal) and children 11 < 16 years old (dermal); and

Golfing: adults (dermal), children 11 < 16 years old (dermal), and children 6 < 11 years 

old (dermal).

The following equations and assumptions were used to calculate post-application risk estimates:

Dermal 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);

TC = transfer coefficient (cm2/hr); and

ET = exposure time (hr/day).

Assumptions:

TTR value is based on chemical-specific study; assumed to be 0.0019 ug/cm2based on 

predicted day 0 residue value calculated by a first-order dissipation kinetics and decay 

model. A summary of the TTR study is presented in the occupational post-application 

section of this document.

Transfer coefficients:

o Physical activities on turf: 180,000 cm2/hr for adults and 49,000 cm2/hr for 

children 1 < 2 years old

o Mowing: 5,500 cm2/hr for adults and 4,500 cm2/hr for children 11 < 16 years old

o Golfing: 5,300 cm2/hr for adults, 4,400 cm2/hr for children 11 < 16 years old, and 

2,900 cm2/hr for children 6 < 11 years old

Exposure time (hr):

o Physical activities on turf: 1.5 hr for adults and children

o Mowing: 1 hr

o Golfing: 4 hr

Hand-to-Mouth:

E = [HR * (FM * SAH) * (ET * N_Replen) * (1- (1- SE)

(Freq_Replen/N-Replen))]

where:

E = exposure (mg/day);

HR = hand residue loading (mg/cm2);

FM = fraction hand surface area mouthed / event (0.127/event);

SAH = typical surface area of one hand (150 cm

2

);

ET = exposure time (1.5 hr/day);

N_Replen = number of replenishment intervals per hour (4 intervals/hour);
Page 19 of 23

SE = saliva extraction factor (0.5); and

Freq_Replen = number of hand-to-mouth contacts events per hour (13.9 events/hour).

and

SA * 2

Faihands *DE HR

H

where:

HR = hand residue loading (mg/cm2);

Faihands = fraction ai on hands compared to total surface residue from dermal 

transfer coefficient study (0.06);

DE = dermal exposure (mg); and

SAH = typical surface area of one hand (150 cm

2

).

Object-to-Mouth:

E = [OR* CF1 * SAMO * (ET * N_Replen) * (1- (1- SEO)

(Freq_Replen/N_Replen))]

where:

E = exposure (mg/day);

OR = chemical residue loading on the object on day “t” (ug/cm2);

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

SAMO = area of the object surface that is mouthed (10 cm

2

/event);

ET = exposure time (1.5 hr/day);

N_Replen = number of replenishment intervals per hour (4 intervals/hour);

SE = saliva extraction factor (0.5); and

Freq_Replen = number of object-to-mouth contact events per hour (8.8 events/hour).

and

OR = AR * FO * CF2 * CF3

where:

OR = chemical residue loading on the object (μg/cm2);

AR = application rate (0.044 lb ai/acre);

FO = fraction of residue available on the object (0.01);

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 10-8

acre/cm2).

Soil ingestion:

E = SRt * SIgR * CF1
Page 20 of 23

where:

E = exposure (mg/day);

SRt = soil residue on day "t" (μg/g);

SIgR = ingestion rate of soil (50 mg/day); and

CF1 = weight unit conversion factor (1 x 10-6g/μg).

and

SRt = AR * FS * (1-FD)

t

* CF2 * CF3 * CF4

where:

SRt = soil residue on day "t" (μg/g);

AR = application rate (0.044 lb ai/acre for short-term and 0.089 lb ai/acre for 

intermediate-term);

FS = fraction of ai available in uppermost cm of soil (1.0/cm);

FD = fraction of residue that dissipates daily (0.1);

t = post-application day on which exposure is being assessed (0);

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

CF3 = area unit conversion factor (1.08 x 10-3ft2/cm2 or 2.47 x 10-8acre/cm2); and

CF4 = soil volume to weight unit conversion factor (0.67 cm3/g soil).

For each scenario, absorbed dose (normalized to body weight) was calculated as:

BW

E*AF D

where:

D = dose (mg/kg-day);

E = exposure (mg/day); 

AF = absorption factor (dermal only; 13%); and

BW = body weight (80 kg for adults; 57 kg for children 11 < 16 years old, 32 kg for 

children 6 < 11 years old, 11 kg for children 1 < 2 years old).

Dermal and incidental oral risk estimates were calculated using the following formula:

MOE = Point of Departure (mg/kg/day) / Dermal or incidental oral dose (mg/kg/day)

where:

Dermal NOAEL = 0.4 mg/kg/day, and 

Incidental oral NOAEL = 0.4 mg/kg/day

Table 5.2.2.1 presents the post-application dermal and incidental oral MOE values calculated for 

the appropriate lifestages after applications of topramezone to turf. Since the toxicological 

effects are similar for dermal versus incidental oral PODs, dermal risks were combined with 

incidental oral risks for children 1 < 2 years old. Post-application risk estimates do not exceed 
Page 21 of 23

HED’s level of concern for any of the scenarios assessed. 

Table 5.2.2.1. Short-Term Residential Post-application Exposure and Risk Estimates for Topramezone.

Lifestage Post-application Exposure Scenario Dose (mg/kg/day) MOEs

Adult

Turf -

sprays

Dermal 

Physical Activities on Turf 0.00083 480

Mowing 1.7 x 10-524,000

Golfing 6.6 x 10-56,100

Child 11 < 16 years old Dermal Mowing 2.0 x 10-5

21,000

Golfing 7.6 x 10-55,200

Child 6 < 11 years old Dermal Golfing 9.0 x 10-54,500

Child 1 < 2 year old

Dermal Physical Activities on Turf 0.0017 240

Hand to Mouth 0.00026 1,500

Object to Mouth 2.1 x 10-519,000

Short-term Incidental Soil Ingestion 1.5 x 10-6270,000

Intermediate-term Incidental Soil Ingestion 3.0 x 10-6130,000

5.3 Combined Exposure

HED combines risk estimates resulting from separate post-application exposure scenarios when 

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

with the exposed population and when the toxicological effects are similar. For topramezone, the 

toxicological effects are similar for the dermal, inhalation and incidental oral routes; therefore, 

the exposures via these routes were combined where appropriate. For residential handlers, 

dermal and inhalation exposures were combined. For post-application scenarios, dermal and 

incidental oral exposures were combined for children 1 < 2 years old.

The incidental oral scenarios (i.e., hand-to-mouth, object-to-mouth, and soil ingestion) should be 

considered inter-related and it is likely that they occur interspersed amongst each other across 

time. Combining all three of these scenarios with the dermal exposure scenario would be overlyconservative because of the conservative nature of each individual assessment. Therefore, the 

post-application exposure scenarios that were combined for children 1 < 2 years old are the 

dermal and hand-to-mouth scenarios. This combination should be considered a protective 

estimate of children’s exposure to pesticides used on turf.
Page 22 of 23

Table 5.3.1. Short- and Intermediate-Term Residential Exposures for the Topramezone Combined Residential Risk Calculations.

Population

Handler Exposure 

(mg/kg/day)1 Residential 

Handler Total 

Exposure 

(mg/kg/day)3

Residential 

Handler 

Total MOE

Post-application Exposure (mg/kg/day)2 Residential 

Postapplication 

Total Exposure 

(mg/kg/day)3

Residential 

Postapplication 

Total MOE Dermal Inhalation Dermal Inhalation Oral

Short-Term

Adult Male 0.00021 8.8 x 10-60.00022 1,800 0.00083 N/A N/A 0.00083 480

Child 11 < 16 years old N/A 7.6 x 10-5 N/A N/A 7.6 x 10-55,200

Child 6 < 11 years old N/A 9.0 x 10-5 N/A N/A 9.0 x 10-54,500

Child 1 < 2 years old N/A 0.0017 N/A 0.00026 0.0019 210

Intermediate-Term

Child 1 < 2 years old N/A N/A N/A 3.0 x 10-63.0 x 10-6130,000

1Handler exposure represents high end inhalation handler exposure, where the exposure duration is appropriate to assess.

2

Postapplication exposure represents high end incidental oral exposure for the relevant exposure duration.

3 For adults, residential total exposure combines the highest dermal and inhalation exposures (Table 4.2.2.1), where applicable. For young children, total residential exposure 

combines high end post application incidental oral AND dermal exposure, where applicable (Table 5.2.2.1). 
Page 23 of 23

5.4 Residential Bystander Post-application Inhalation Language

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

assessment was not performed for topramezone at this time. However, 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 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 postapplication 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 topramezone.

5.5 Spray Drift

Spray drift is always a potential source of exposure to residents nearby to spraying operations. 

This is particularly the case with aerial application, but, to a lesser extent, could also be a 

potential source of exposure from the ground application method employed for topramezone. 

The Agency has been working with the Spray Drift Task Force, 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 at 

http://www.epa.gov/opp00001/factsheets/spraydrift.htm). On a chemical by chemical basis, the 

Agency is now requiring interim mitigation measures for aerial applications that must be placed 

on product labels/labeling. The Agency has completed its evaluation of the new database 

submitted by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is 

developing a policy on how to appropriately apply the data and the AgDRIFT computer model to 

its risk assessments for pesticides applied by air, orchard airblast and ground hydraulic methods. 

After the policy is in place, the Agency may impose further refinements in spray drift 

management practices to reduce off-target drift with specific products with significant risks 

associated with drift.