Page 3 of 16

1.0 Executive Summary

Azoxystrobin is a broad spectrum fungicide that controls plant diseases on agricultural crops, turf 

and ornamentals, and controls molds and fungi on indoor surfaces. The following formulated 

liquid end use products (EPs) are evaluated in this assessment:

(1) Abound Flowable Fungicide (22.9% ai), EPA Reg. No. 100-1098;

(2) Quilt Fungicide, (7% azoxystrobin, 11.7% propiconazole), EPA Reg. No. 100-1178; and 

(3) Quilt Xcel Fungicide (13.5% azoxystrobin, 11.7% propioconazole); EPA Reg. No. 100-1324.

In this document, the name azoxystrobin will be used for the active ingredient (ai) in these 

products. Occupational and residential exposure and risk estimates of propiconazole will be 

assessed in a separate document.

Proposed Use Profile:

Azoxystrobin is proposed for use as a foliar application on cereal grain crops using ground, aerial 

and chemigation equipment. The use profile is summarized in Table 4.2. Proposed single 

application rates on all proposed crops range from 0.030-0.20 lb ai/A.

Hazard Concerns: 

In a 21-day repeated dose dermal study in the rat, no dermal or systemic toxicity was seen at the 

limit dose (1,000 mg/kg/day). Furthermore, there was no concern for developmental or 

reproductive effects. Therefore, no hazard was identified for short- and intermediate-term 

dermal exposure scenarios, and a dermal risk assessment is not applicable at this time. The point 

of departure (POD) chosen for short-term inhalation risk assessment is based on a developmental 

toxicity study in rats in which maternal effects (increased diarrhea, urinary incontinence and 

salivation) were observed at the lowest observed adverse effect level (LOAEL) of 100 

mg/kg/day. An oral no observed adverse effect level (NOAEL) of 25 mg/kg/day was identified 

as the POD for the short-term inhalation risk assessment. The POD chosen for intermediate-term 

inhalation risk assessment is based on a 90-day rat feeding study in which decreased body weight 

gain and clinical signs indicative of reduced nutrition were seen at the LOAELs of 211 (males) 

and 223 (females) mg/kg/day. An oral NOAEL of 20 mg/kg/day was identified as the POD for 

the intermediate-term inhalation risk assessment. Since the selected toxicological PODs are not 

based on developmental effects, the average adult body weight of 80 kg was used for estimating 

short- and intermediate-term inhalation doses. Since no inhalation absorption data are available, 

toxicity by the inhalation route is considered to be equivalent to the toxicity by the oral route of 

exposure. Azoxystrobin is characterized as "not likely" to be a human carcinogen. 

Residential Exposure:

There are no proposed residential uses at this time; however, there are existing residential uses 

that have been previously reassessed to reflect updates to HED’s 2012 Residential SOPs1along 

with policy changes for body weight assumptions (DP394287, K. Rury, 03/30/2012). All 

residential risk estimates resulted in MOEs > 100 and, therefore, are not of concern to HED.

 

1 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Page 4 of 16

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

inhalation exposure assessment was not performed for azoxystrobin 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 azoxystrobin.

Occupational Exposure:

Based on the proposed use pattern of azoxystrobin, there is a potential for short- and 

intermediate-term occupational exposure during handling (mixing, loading, and applying) and 

post-application activities. Chronic exposure is not expected for the proposed use patterns. 

Occupational Handlers:

The results of the occupational handler exposure and risk assessment estimates indicate that 

short- and intermediate-term inhalation MOEs are not of concern to HED (i.e. MOEs > 100) with 

baseline mitigation (no respirator). The short-term inhalation MOEs range from 38,000 to 

570,000 for occupational handlers. The intermediate-term MOEs range from 30,000 to 460,000 

for occupational handlers. 

Agricultural Post-Application:

Although occupational dermal exposure is expected following treatment of cereal grain crops, 

dermal hazard was not identified for azoxystrobin. Therefore, a quantitative post-application 

dermal risk assessment was not conducted.

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

inhalation exposure assessment was not performed for azoxystrobin 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 azoxystrobin.

A chemical-specific dislodgeable foliar residue (DFR) study is available for the use of

azoxystrobin on grapes, but has not been employed in this or previous risk assessments because 

HED determined there is no hazard via the dermal route. 

Restricted Entry Interval (REI):

The REI specified on the proposed label is based on the acute toxicity of azoxystrobin. Based on 

the Worker Protection Standard (WPS), a 12-hour restricted entry interval (REI) is required for 

chemicals classified under Toxicity Category III or IV. Since azoxystrobin is classified as 

Toxicity Category III for acute dermal and primary eye irritation and Toxicity Category IV for 

primary skin irritation, the 12-hour REI listed on the two mixed active ingredient (MAI) labels 

(Quilt Fungicide and Quilt Xcel Fungicide) is appropriate.

For the Abound label, HED previously determined that the REI could be reduced to 4 hours. 

Although a 12-hour REI is the shortest waiting period permitted under the WPS, REIs may be

further reduced from 12 hours if certain criteria are met for both the technical material and the 

different end-use products in accordance with the Pesticide Registration (PR) Notice 95-3 

[Reduction of Worker Protection Standard (WPS) Interim Restricted Entry Intervals (REIs) for 
Page 5 of 16

Certain Low Risk Pesticides].2 Since these criteria have been met for both the technical and the 

EP, the 4-hour REI listed on the Abound label is appropriate.

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 and the AHETF database, are (1) subject to ethics review pursuant to 40 CFR 26, (2) 

have received that review, and (3) are compliant with applicable ethics requirements. For certain 

studies, the ethics review may have included review by the Human Studies Review Board. 

Descriptions of data sources, as well as guidance on their use, can be found at the Agency 

website3. 

2.0 Summary of Conclusions and Data Requirements

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

uses of azoxystrobin. 

Residue Data 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. However, a TTR study is not required for 

azoxystrobin at this time because dermal and systemic toxicity were not seen in a 21-day 

repeated dose dermal study in the rat up to the limit dose (1,000 mg/kg/day). Additionally, all 

incidental oral risk estimates from azoxystrobin use on turf result in MOEs ≥ 1,800 (with an 

LOC of 100).

3.0 Hazard Characterization

The toxicological doses and endpoints supporting this petition remain unchanged and have been 

summarized in the previous human health risk assessment (DP394285, K. Rury, 04/30/2012).

Acute Toxicity

Table 3.1. Acute Toxicity Data on Technical Azoxystrobin. 

Guideline

No. Study Type MRID # Results Toxicity Category

870.1100 Acute Oral - Rat 43678122 LD50 > 5000 mg/kg (Limit Test) in Males & Females IV

870.1200 Acute Dermal - Rat 43678124 LD50 > 2000 mg/kg (Limit Test) in Males & Females III

870.1300 Acute Inhalation -

Rat 43678126

LC50 Males = 0.962 mg/L (95% C.I. = 0.674)

Females = 0.698 mg/L (95% C.I. = 0.509, 2.425)

The combined LC50 was not calculated

due to mortality pattern

III

870.2400 Primary Eye 

Irritation - Rabbit 43678128

Slight to moderate erythema and slight chemosis in all 

rabbits within one hour, but effects resolved within 48 

hours of treatment.

III

 

2 Available: http://www.epa.gov/PR_Notices/pr95-3.html

3

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

http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 6 of 16

Table 3.1. Acute Toxicity Data on Technical Azoxystrobin. 

Guideline

No. Study Type MRID # Results Toxicity Category

870.2500 Primary Skin 

Irritation - Rabbit 43678130 Very slight erythema and edema that persisted for three days on one rabbit and for one hour on another. IV

870.2600 Dermal Sensitization 

- Guinea Pig 43678132 No erythema or edema were found 38 or 48 hrs after challenge with test material.

Not a dermal 

sensitizer

Toxicological PODs Used for Risk Assessment

Table 3.2. Summary of Toxicological Doses and Endpoints for Azoxystrobin for Use in Dietary, NonOccupational and Occupational Human Health Risk Assessments.1

Exposure/

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment

Study and Toxicological Effects

Incidental Oral 

Short-Term (1-30 

days)

NOAEL = 25 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA SF = 1X

Residential 

LOC for MOE 

= 100

Prenatal Developmental Oral Toxicity – Rat. 

LOAEL = 100 mg/kg/day based on increased 

maternal diarrhea, urinary incontinence, and 

salivation.

Incidental Oral 

IntermediateTerm (1-6 

months)

NOAEL = 20 

mg/kg/day

UFA = 10X

UFH = 10X

FQPA SF = 1X

Residential 

LOC for MOE 

= 100

90-day Feeding Study – Rat. LOAEL = 211/223 

mg/kg/day (M/F) based on decreased body 

weight gain in both sexes and clinical signs 

indicative of reduced nutrition.

Dermal

(All Durations) No hazard was identified for this exposure scenario.

21-Day Repeated Dose Dermal Study – Rat. No 

dermal or systemic toxicity was seen at the limit 

dose (1,000 mg/kg/day).

Inhalation ShortTerm (1-30 days)Oral NOAEL 

= 25

UFA = 10X

UFH = 10X

FQPA SF = 1X

Occupational & 

Residential 

LOC for MOE 

= 100

Prenatal Developmental Oral Toxicity – Rat. 

LOAEL = 100 mg/kg/day based on increased 

maternal diarrhea, urinary incontinence, and 

salivation.

Inhalation 

IntermediateTerm

(1-6 months)

Oral NOAEL 

= 20

UFA = 10X

UFH = 10X

FQPA SF=1X

Occupational & 

Residential 

LOC for MOE 

= 100

90-day Feeding Study – Rat. LOAEL = 211/223 

mg/kg/day (M/F) based on decreased body 

weight gain in both sexes and clinical signs 

indicative of reduced nutrition.

Cancer

(oral, dermal, 

inhalation)

Azoxystrobin is classified as "Not Likely" to be carcinogenic to humans.

1 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. PAD = 

population adjusted dose (a = acute, c = chronic). RfD = reference dose. MOE = margin of exposure. LOC = 

level of concern. N/A = not applicable.

4.0 Use Profile

Syngenta has submitted proposed use directions (Section B) for the following liquid EPs: (1) 

Abound Flowable Fungicide, EPA Reg. No. 100-1098; (2) Quilt Fungicide, EPA Reg. No. 100-

1178; and (3) Quilt Xcel Fungicide; EPA Reg. No. 100-1324. Table 4.1 summarizes the 

registered EPs, while Table 4.2 presents the proposed use directions on each of the proposed 

cereal grains (barley, oats, rye, wheat, and triticale).
Page 7 of 16

Table 4.1. Summary of Proposed Azoxystrobin End-Use Products.

Trade Name Reg. No. % ai of formulation Formulation 

Type

Target Crop Source

Abound 

Flowable 

Fungicide

100-1098 22.9% azoxystrobin

(2.08 lb ai/gal) SC

Cereals Grains 

(barley, oats, rye, 

wheat, triticale)

Undated supplemental label 

included in Section B of the 

petition.

Quilt

Fungicide 100-1178

7% azoxystrobin

(0.62 lb ai/gal)

11.7% propiconazole

(1.04 lb ai/gal)

EC

Quilt Xcel

Fungicide 100-1324

13.5% azoxystrobin

(1.18 lb ai/gal)

11.7% propiconazole

(1.02 lb ai/gal)

EC

Table 4.2. Summary of Directions for Use of Azoxystrobin.

Applic. 

Timing, Type, 

and Equip.

Formulation 

[EPA Reg. 

No.]

Applic. 

Rate (fl 

oz and lb 

ai/A)

Max. No. 

Applic. per 

Season1

Max. Seasonal 

Applic. Rate 

(fl oz and lb 

ai/A)

PHI 

(days) Use Directions and Limitations2

Cereals (Wheat, Triticale)

Foliar:

Ground, 

Aerial or 

Chemigation

2.08 lb 

ai/gal SC

[100-1098]

4.0-12

(0.07-

0.20)

2

24

(0.40)

7

forage 

and hay 

Applications are to be made prior to 

disease development.

Minimum volume for air applications is 

5 gal/A.

Foliar:

Ground, 

Aerial or 

Chemigation

MAI 

(0.62 lb 

ai/gal)

[100-1178]

7-14

(0.03-

0.07)

2

28

(0.14)

7

forage 

and hay 

Apply Quilt in the spring for suppression 

of early season diseases. Follow up with 

a second application for full season 

control. Protecting the flag leaf is 

important for maximizing yield. For high 

yields apply Quilt when flag leaf is 50% 

to full head emergence (Feekes 10.5).

Foliar:

Ground, 

Aerial or 

Chemigation

MAI 

(1.18 lb 

ai/gal)

[100-1324]

7-14

(0.06-

0.13)

2

28

(0.26)

7

forage 

and hay 

Cereals (Barley, Oat and Rye) 100-1178, 100-1324 includes Triticale

Foliar:

Ground, 

Aerial or 

Chemigation

2.08 lb 

ai/gal SC

[100-1098]

6-12

(0.10-

0.20)

2

24

(0.40)

7

forage 

and hay 

Applications are to be made prior to 

disease development.

Minimum volume for air applications is 

5 gal/A.

Foliar:

Ground, 

Aerial or 

Chemigation

MAI 

(0.62 lb 

ai/gal)

[100-1178]

7-14

(0.03-

0.07)

2

28

(0.14)

7

forage 

and hay 

Apply Quilt in the spring for suppression 

of early season diseases. Follow up with 

a second application for full season 

control. Protecting the flag leaf is 

important for maximizing yield. For high 

yields apply Quilt when flag leaf is 50% 

to full head emergence (Feekes 10.5).

Foliar:

Ground, 

Aerial or 

Chemigation

MAI 

(1.18 lb 

ai/gal)

[100-1324]

7-14

(0.06-

0.13)

2

28

(0.26)

7

forage 

and hay 

1 For resistance management, no more than two sequential applications of Abound Flowable Fungicide or other

Group 11 fungicides should be made before alternating with a fungicide having a different mode of action (not in 

Group 11). Do not make more than two foliar applications of Abound Flowable Fungicide or other Group 11 

fungicide per season.

2 Applications may be made no closer than a 14-day interval.

Do not apply after Feekes 10.54.

Do not apply more than 0.40 lb ai/A per season of azoxystrobin-containing products.

The azoxystrobin product labels direct mixers, loaders, applicators and other handlers to wear a 

long-sleeved shirt, long pants, chemical-resistant gloves made of any waterproof material (such 

as polyvinyl chloride, nitrile, rubber or butyl rubber), shoes plus socks, and protective eyewear.
Page 8 of 16

5.0 Residential Exposure and Risk Estimates

There are no proposed residential uses at this time; however, there are existing residential uses 

that have been previously reassessed to reflect updates to HED’s 2012 Residential SOPs4along 

with policy changes for body weight assumptions (DP394287, K. Rury, 03/30/2012).

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 as was described above for 

occupational handlers. 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.

Summary of Residential Handler Non-Cancer Exposure and Risk Estimates

The MOEs for adult handlers ranged from 2,400 (painting with an airless sprayer) to 

1,000,000,000 (M/L/A a wettable powder to gardens and trees using a hose-end sprayer).

Table 5.1. Short-Term Residential Handler Non-Cancer Exposure and Risk Estimate for Azoxystrobin.

Exposure Scenario Level of 

Concern

Inhalation 

Unit Exposure

(μg/lb ai)

Maximum 

Application 

Rate1

Area Treated or 

Amount Handled 

Daily2

Inhalation

Dose 

(mg/kg/day)3 MOE4

Applicator

Painting with Airless Sprayer 100 0.56 1.0% ai by 

weight 5 one-gallon cans 0.0149 2,400

Painting with a Brush 100 0.2 1.0% ai by 

weight

2 one-gallon 

cans

0.0005 50,000

Indoor Manually-Pressurized 

Handwand Wettable Powder 100 1.1 0.0047 (lb 

ai/gal) 0.5 gallons 0.000032 770,000

Indoor Manually-Pressurized 

Handwand Wettable Powder in 

WSB

100 1.1 0.0047 (lb 

ai/gal) 0.5 gallons 0.000032 770,000

M/L/A Wettable Powders to Turf 

[Hose End Sprayer] 100 0.022 0.95 (lb ai/A) 0.5 acres 0.00013 190,000

M/L/A Wettable Powder to Turf 

[Manually Pressurized Handwand 

or Backpack Sprayer]

100 1.1 0.011 (lb 

ai/gal) 5 gallons 0.00076 33,000

M/L/A Wettable Powders in 

WSB to Turf [Hose End Sprayer] 100 0.034 0.95 (lb ai/A) 0.5 acres 0.0002 120,000

M/L/A Wettable Powder in WSB 

to Turf [Manually Pressurized 

Handwand or Backpack Sprayer]

100 0.018 0.011 (lb 

ai/gal) 5 gallons 0.000012 2,000,000

M/L/A Wettable Powder 

Azoxystrobin to Gardens and 

Trees [Manually-Pressurized 

Handwand or Backpack Sprayer]

100 1.1 0.000125 (lb 

ai/gal) 5 gallons 0.0000086 2,900,000

 

4 Available: http://www.epa.gov/pesticides/science/residential-exposure-sop.html
Page 9 of 16

Table 5.1. Short-Term Residential Handler Non-Cancer Exposure and Risk Estimate for Azoxystrobin.

Exposure Scenario Level of 

Concern

Inhalation 

Unit Exposure

(μg/lb ai)

Maximum 

Application 

Rate1

Area Treated or 

Amount Handled 

Daily2

Inhalation

Dose 

(mg/kg/day)3 MOE4

M/L/A Wettable Powder 

Azoxystrobin to Gardens and 

Trees [Hose-End Sprayer]

100 0.0014 0.000125 (lb 

ai/gal) 11 gallons 0.000000024 1,000,000,000

M/L/A Wettable Powder Water 

Soluble Packets Azoxystrobin to 

Gardens and Trees [ManuallyPressurized Handwand or 

Backpack Sprayer]

100 0.018 0.000125 (lb 

ai/gal) 5 gallons 0.00000014 180,000,000

M/L/A Wettable Powder Water 

Soluble Packets Azoxystrobin to 

Gardens and Trees [Hose-End 

Sprayer]

100 0.034 0.000125 (lb 

ai/gal) 11 gallons 0.00000059 43,000,000

1 Based on registered or proposed label (Reg. No. 100-1229).

2 Exposure Science Advisory Council Policy #9.1.

3 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) x Conversion Factor (0.001 mg/μg) x Application Rate (lb ai/acre or gal) x Amount 

Handled (gallons/day) / BW (kg).

4 Inhalation MOE = Inhalation NOAEL (mg/kg/day) / Inhalation Dose (mg/kg/day). Short-term Inhalation NOAEL = 25 mg/kg/day.

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 azoxystrobin. Residential exposure is 

expected to be short-term in duration.

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

Although residential dermal exposure is expected following treatment of turf, no dermal hazard 

was identified for azoxystrobin. Therefore, a quantitative post-application dermal risk 

assessment was not conducted. The exposure and risk estimates for all residential postapplication uses result in risk estimates that are greater than the LOC MOE of 100, and therefore 

are not of concern to HED. The MOEs ranged from 250 to 810,000 for incidental oral ingestion

of azoxystrobin in indoor and outdoor environments. The highest residential non-cancer 

exposures and risk estimates resulted from indoor post-application inhalation exposure from 

broadcast carpet use (MOEs were 220,000,000,000 for adults and 52,000,000,000 for children).

Table 5.2. Highest Residential Post-Application Non-Cancer Exposure and Risk Estimates for Azoxystrobin.

Lifestage Post-Application Exposure Scenario Dose

(mg/kg/day) MOEs

Adult

Indoor Carpet - Broadcast

Inhalation 0.00000000011 220,000,000,000

Child

Inhalation 0.00000000087 52,000,000,000

Hand to Mouth 0.098 250

5.3 Combined Residential Risk Estimates (Multiple Exposure Scenarios)

Residential handler and post-application scenarios do not need to be combined. Although there 

is potential for the same individual (i.e. an adult) to apply a pesticide in and around the home and 

be exposed by reentering a treated area in the same day, it is inappropriate to combine both of 

these exposure scenarios because of the conservative nature of each individual assessment.
Page 10 of 16

5.4 Residential Risk Estimates for Use in Aggregate Assessment

Table 5.4 reflects the high-end residential risk estimates that are recommended for use in the 

aggregate assessment for azoxystrobin.

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

inhalation exposure from handlers applying paint via airless sprayers.

The recommended residential exposure for use in the children 1 to <2 years old aggregate 

assessment reflects inhalation and hand-to-mouth exposures from post-application 

exposure to indoor applications to carpets.

Table 5.4. Recommendations for the Residential Exposures for the Azoxystrobin Aggregate Assessment.

1

Lifestage

Handler Exposure 

(mg/kg/day)2 Residential 

Handler Total 

MOE3

Post-Application Exposure 

(mg/kg/day)

Residential PostApplication Total 

Exposure 

(mg/kg/day)4

Residential PostApplication 

MOE5

Inhalation Inhalation Oral

Short-Term

Adult 0.0149 2,400 N/A N/A N/A N/A

Child N/A N/A 0.00000000087 0.0982 0.0982 250

1 N/A = not applicable. Adult post-application exposures do not need to be aggregated with the handler exposures, and children 

handler exposures are not expected. For adults, the residential total exposure is equivalent to the inhalation exposure (Table 

5.1). For young children, total residential exposure combines high-end inhalation and post-application incidental oral exposure 

(Table 5.2).

2 Handler exposure represents high-end handler exposure (i.e. the highest handler exposure of all scenarios assessed).

3 Total MOE = Inhalation MOE = NOAEL / Inhalation Exposure. Short-Term Inhalation NOAEL = 25 mg/kg/day.

4 Post-application exposure represents high-end inhalation and/or incidental oral exposure for the relevant exposure duration.

5 Total MOE = NOAEL ÷ (Inhalation Exposure + Incidental Oral Exposure). Inhalation NOAEL = Incidental Oral NOAEL = 

25 mg/kg/day.

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 azoxystrobin. 

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 information5. 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 risk estimates associated with drift.

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

performed as a result of pesticide drift from neighboring treated agricultural fields, an inhalation 

 

5 Available: http://www.epa.gov/opp00001/factsheets/spraydrift.htm 
Page 11 of 16

exposure assessment was performed for flaggers. This exposure scenario is representative of a 

worse case inhalation (drift) exposure and may be considered protective of most outdoor 

agricultural and commercial post-application inhalation exposure scenarios. 

5.6 Residential Bystander Post-Application Inhalation Exposure

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

assessment was not performed for azoxystrobin at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category III), low vapor pressure (8.2x10-13 mm Hg at 20oC), and 

the low proposed use rate (0.20 lb ai/A). 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, 20106. 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 

azoxystrobin.

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 proposed uses. 

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

following scenarios: 

Mixing/loading liquids for groundboom, aerial, and chemigation application,

Applying liquids via groundboom and aircraft, and

Flagging for aerial application.

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: See Section 4.0.

 

6 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html
Page 12 of 16

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 and the AHETF database. 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 Table7”, 

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 website8. 

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. However, the azoxystrobin product labels direct mixers, loaders, applicators and 

other handlers to wear a long-sleeved shirt, long pants, chemical-resistant gloves made of any 

waterproof material (such as polyvinyl chloride, nitrile, rubber or butyl rubber), shoes plus socks, 

and protective eyewear.

Area Treated or Amount Handled: Based on HED ExpoSAC Policy 9.1, the amount treated or 

handled per day was assumed to be: 

80 acres for mixing/loading for groundboom applications and applying via ground

equipment on barley, oats, and rye,

350 acres for mixing/loading for aerial applications and applying via aircraft on barley, 

oats, and rye,

200 acres for mixing/loading groundboom applications and applying via ground 

equipment on wheat and triticale,

1200 acres for mixing/loading for aerial applications and applying via aircraft on wheat 

and triticale, and

350 acres for flagging for aerial application on all cereal grain crops.

 

Body Weight: 

The standard body weight for the general population (80 kg) was used for all exposure scenarios 

covered in this risk assessment since the endpoints selected were not developmental and/or fetal 

effects.

 

Absorption Factors: 

Since inhalation absorption data are not available, toxicity by the inhalation route is considered 

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

Exposure Duration:

HED classifies exposures from 1 to 30 days as short-term and exposures 30 days to six months 

as intermediate-term. Exposure duration is determined by many things, including the exposed 

population, the use site, the pest pressure triggering the use of the pesticide, and the cultural 

practices surrounding that use site. For most agricultural uses, it is reasonable to believe that 

 

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

8 Available: http://www.epa.gov/pesticides/science/handler-exposure-data.html
Page 13 of 16

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).

Based on the proposed uses for azoxystrobin, short- and intermediate-term exposures are

expected for the following reasons: (1) two applications can be made per season with a 

minimum retreatment interval (RTI) of 14 days; and (2) azoxystrobin is a broad spectrum 

fungicide which may be used for both early season suppression and full season control.

Mitigation/Personal Protective Equipment: Occupational handler exposure assessments are 

completed by HED using different levels of risk mitigation. Typically, HED uses a tiered 

approach. The lowest tier is designed as the baseline exposure scenario (i.e. long-sleeve shirt, 

long pants, shoes, socks, no respirator). If risk estimates are of concern at baseline attire, then 

increasing levels of PPE (i.e. gloves, respirators) are evaluated. If risk estimates remain a 

concern with maximum PPE, then engineering controls (i.e. enclosed cabs or cockpits, watersoluble packaging, and closed mixing/loading systems) are evaluated. This approach is used to 

ensure that the lowest level of risk mitigation that provides adequate protection is selected, since 

the addition of PPE and engineering controls involves an additional expense to the user and (in 

the case of PPE) also involves an additional burden to the user due to decreased comfort and 

dexterity and increased heat stress and respiratory stress.

Occupational Handler Non-Cancer Exposure and Risk Estimate Equations

Potential daily exposures for occupational handlers were calculated using the following formula:

Daily Exposure (mg ai /day) = UE (μg ai / lb ai) × AR (lb ai /A) × AT (A /day) × 1E-3 mg/μg

where:

Daily Exposure = Amount (mg ai/day) that is available for inhalation absorption,

UE = Unit Exposure (μg ai / lb ai),

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

AT = daily acres treated (A /day).

The daily doses were calculated using the following formula:

Average Daily Dose (mg ai/kg/day) = [Daily Exposure (mg ai/day) × Absorption (%)]

Body Weight (kg)

where:

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

pesticide active ingredient/kg body weight/day),

Daily Exposure = Amount (mg ai/day) that is available for inhalation absorption,

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

(%), and

Body Weight = Body weight determined to represent the population of interest in a risk assessment (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 inhalation dose received by occupational handlers were

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

each exposure route. All MOE values were calculated using the following formula:

MOE = POD (typically a NOAEL in mg/kg/day) 

ADD (mg/kg/day)

where:
Page 14 of 16

MOE = Margin of Exposure: value used by HED to represent risk or risk estimates (unitless),

POD = Point of Departure,

NOAEL = No Observed Adverse Effect Level (mg/kg/day): Dose level in a toxicity study, where no observed 

adverse effects occurred in the study, and

ADD = Average Daily Dose (mg/kg/day): the absorbed dose received from exposure to a pesticide in a given 

scenario.

Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates

The short-term occupational handler inhalation exposure risk estimates are not of concern to 

HED with baseline mitigation (Table 6.1). With baseline mitigation (no respirator), the 

inhalation MOEs for occupational handlers of azoxystrobin to cereal grain crops range from 

38,000 to 570,000. The intermediate-term occupational handler inhalation exposure risk 

estimates are not of concern to HED with baseline mitigation (Table 6.1). With baseline 

mitigation (no respirator), the inhalation MOEs for occupational handlers of azoxystrobin to 

cereal grain crops range from 30,000 to 460,000. 

The Agency has evaluated scenarios that may be limited in nature such as flagging during aerial 

applications because engineering controls (i.e. Global Positioning Satellite technology) are now 

predominantly used as indicated by the 1998 National Agricultural Aviation Association 

(NAAA) survey of their membership. It appears, however, flaggers are still used in 

approximately 10 to 15 percent of aerial application operations. In cases like these, the Agency 

strongly encourages the use of the engineering control system but will continue to evaluate risks 

for flaggers and any other population where a clear exposure pathway exists until the potential 

for exposure is eliminated. The Agency is aware that NAAA is conducting another survey on 

exposure issues and will consider those results as are timely and appropriate.

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); pilots are not required to wear protective gloves. With this level of protection, there 

are no risk estimates of concern for applicators.

Table 6.1. Short- and Intermediate-Term Occupational Exposure and Risk Estimates for Proposed Use of 

Azoxystrobin on Cereal Grains (Barley, Oats, Rye, Wheat, and Triticale). All estimates are at baseline 

mitigation (single layer without gloves or respiratory protection). 

Exposure Scenario Crop(s)

Baseline 

Inhalation 

Unit 

Exposure 

(μg/lb ai)1

Maximum

Application 

Rate (lb 

ai/A)2

Area 

Treated or 

Amount 

Handled 

Daily3

Inhalation

Dose 

(mg/kg/day)4

Short-Term 

MOE5

IntermediateTerm MOE6

Mixer/Loader

Mixing/Loading Liquids for 

Groundboom Application

Barley, Oats, 

Rye

0.219 0.20

80 0.000044 570,000 460,000

Wheat, 

Triticale 200 0.00011 230,000 180,000

Mixing/Loading Liquids for 

Aerial and Chemigation 

Application

Barley, Oats, 

Rye 350 0.00019 130,000 100,000

Wheat, 

Triticale 1200 0.00066 38,000 30,000
Page 15 of 16

Table 6.1. Short- and Intermediate-Term Occupational Exposure and Risk Estimates for Proposed Use of 

Azoxystrobin on Cereal Grains (Barley, Oats, Rye, Wheat, and Triticale). All estimates are at baseline 

mitigation (single layer without gloves or respiratory protection). 

Exposure Scenario Crop(s)

Baseline 

Inhalation 

Unit 

Exposure 

(μg/lb ai)1

Maximum

Application 

Rate (lb 

ai/A)2

Area 

Treated or 

Amount 

Handled 

Daily3

Inhalation

Dose 

(mg/kg/day)4

Short-Term 

MOE5

IntermediateTerm MOE6

Flagger

Flagging for

Aerial Application

Barley, Oats, 

Rye, Wheat, 

Triticale

0.35 0.20 350 0.00031 82,000 65,000

Applicator

Applying Sprays via 

Groundboom Equipment

Barley, Oats, 

Rye

0.34

0.20

80 0.000068 370,000 290,000

Wheat, 

Triticale 200 0.00017 150,000 120,000

Applying Sprays via

Aerial Equipment *

Barley, Oats, 

Rye

0.068

350 0.000060 420,000 340,000

Wheat, 

Triticale 1200 0.00020 120,000 98,000

1 Based on “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2012); includes data from PHED /AHETF. 

Level of mitigation: Baseline.

2 Based on registered labels with proposed new uses (Reg. Nos. 100-1098, 100-1178, 100-1324).

3 Exposure Science Advisory Council Policy #9.1.

4 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre) × Area Treated Daily

(A/day) ÷ BW (kg). Bodyweight = 80 kg.

5 Inhalation MOE = Inhalation NOAEL (mg/kg/day) ÷ Inhalation Dose (mg/kg/day). Short-Term Inhalation NOAEL = 25 mg/kg/day.

6 Inhalation MOE = Inhalation NOAEL (mg/kg/day) ÷ Inhalation Dose (mg/kg/day). Intermediate-Term Inhalation NOAEL = 20 mg/kg/day.

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 Dermal Exposure/Risk Estimates

The proposed occupational uses for azoxystrobin addressed in this document result in the 

potential for exposure to azoxystrobin during scouting, hand weeding, and hand harvesting. 

However, no appropriate dermal endpoint was identified for azoxystrobin. Therefore, an 

assessment of occupational dermal post-application exposure to azoxystrobin was not conducted. 

A chemical-specific dislodgeable foliar residue (DFR) study is available for the use of 

azoxystrobin on grapes, but has not been employed in this or previous risk assessments because 

HED determined there is no hazard via the dermal route. 
Page 16 of 16

Restricted Entry Interval

The REI specified on the proposed label is based on the acute toxicity of azoxystrobin. Based on 

the Worker Protection Standard (WPS), a 12-hour restricted entry interval (REI) is required for 

chemicals classified under Toxicity Category III or IV. Since azoxystrobin is classified as 

Toxicity Category III for acute dermal and primary eye irritation and Toxicity Category IV for 

primary skin irritation, the 12-hour REI listed on the two MAI labels (Quilt Fungicide and Quilt 

Xcel Fungicide) is appropriate.

For the Abound label, HED previously determined that the REI could be reduced to 4 hours. 

Although a 12-hour REI is the shortest waiting period permitted under the WPS, REIs may be

further reduced from 12 hours if certain criteria are met for both the technical material and the 

different end-use products in accordance with the Pesticide Registration (PR) Notice 95-3 

[Reduction of Worker Protection Standard (WPS) Interim Restricted Entry Intervals (REIs) for 

Certain Low Risk Pesticides].9 Since these criteria have been met for both the technical and the 

EP, the 4-hour REI listed on the Abound label is appropriate.

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 azoxystrobin at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category III), low vapor pressure (8.2x10-13 mm Hg at 20oC), and 

the low proposed use rate (0.20 lb ai/A). However, there are multiple potential sources of postapplication 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, 201010. 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 azoxystrobin.

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.

 

9 Available: http://www.epa.gov/PR_Notices/pr95-3.html

10 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html