Encouraging the Use of Drift 

Reduction Technologies

In the United States

Environmental Modeling Public Meeting

Washington, D.C 

April 28, 2015

Anne Overstreet, Charles Peck and Faruque Khan, 

Office of Pesticide Programs, US EPA

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OVERVIEW

• Background

• Key Points of the DRT Program

• Risk Assessment Processes

• Risk Mitigation and DRT Application

• References/Links
BACKGROUND

Why Interest in Spray Drift Reduction

700 million pounds of pesticides are sprayed on 800 million crop 

acres annually.

1 – 10% of the spray (smallest droplets) drifts and deposits on 

other sites:

 70 millions pounds of pesticide active ingredient

 Value of $660 million

Thousands of complaints reported annually to state pesticide 

regulatory agencies; many (most?) complaints resolved privately.

Spray drift is a component of EPA’s pesticide risk assessment.

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Drift Reduction Technology Program

 Launched October 2014

 Accelerate use of application technologies 

verified to significantly reduce spray drift

 Encourage technology and pesticide 

manufacturers to voluntarily participate

 EPA can credit use of DRTs in registration 

decisions and registration reviews

 Significant enthusiasm by agriculture 

industry
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Key Point 1: Technology manufacturers 

volunteer to test technologies

 DRT standard test protocol

 Test technology against a standard nozzle 

for comparison

 For nozzles: ASABE S572.1 fine/medium 

boundary reference nozzle 

 For nozzle plus adjuvant/formulation: ASABE 

S572.1 reference nozzle at the lower boundary 

in the which the test system falls (e.g. if a coarse 

nozzle is used with adjuvant/formulation to test 

drift reduction, ASABE572.1 coarse nozzle 

would be the reference nozzle). 

 Wind tunnels for droplet size 

distributions

 Field studies for deposition
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Key Point 2: EPA’s Office of Pesticide 

Programs (OPP) reviews test results and 

determines DRT-star rating for technology

 Four ratings:

 Rating is percent difference between technology 

and standard nozzle.

DRT* 25-49 %

DRT** 50-74 %

DRT*** 75-89 %

DRT**** 90+ %
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Key Point 3: Example of DRT ratings on 

future OPP-DRT webpage
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Factors Considered in Risk 

Assessments

 Use Patterns

 Formulation Type 

 Chemical Properties 

 Methods of Application

 Sources of Exposure 

 Routes of Exposure

 Durations of Exposure

 Hazard (Toxicity)
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Spray Drift in Risk Assessments

• Spray drift is one route of exposure considered in EFED 

risk assessments

• Spray drift is normally included in

 Terrestrial plant exposure estimates

 Aquatic exposure estimates

 Human drinking water exposure estimates

 Off-site terrestrial animal exposure estimates
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Generic Scenario for Spray Drift

Spray Drift Exposure in the Environment
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Key Inputs/Assessment Summary

Drift will occur and can have impacts

• Labeled uses/restrictions

• Amount which drifts: AgDRIFT/AGDISP models

• Exposures: models, assessment methods

• Risk: calculated based on chemical specific toxicity 

information

• Characterize: discuss the uncertainties and the overall 

issues to describe risk picture
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Spray Drift Values Derived from 

AgDRIFT Model

Application 

Type

Tier I AgDRIFT

Application Parameters

Aerial

Fine to medium (Dv0.5 - 255mm)

Release height-10 ft

Wind speed – 10 mph

Spray volume – 2 gallon

Swath displacement-37%

Ground Boom

Very fine to fine (Dv0.5 - 175mm)

High boom (50”)

Data - 90th%ile

Airblast Sparse 

(young and dormant)
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Process for Considering Spray Drift in Risk 

Assessments

13

Evaluate importance of spray drift in 

exposure assessment

Describe spray drift’s 

contribution to 

exposure/risk

Spray drift is NOT 

a significant source 

of exposure/risk

No more spray drift 

work required

Spray drift IS a 

significant source 

of exposure/risk

Review labels for mandatory 

vs advisory language on: 

- Droplet size

- Wind speed

- Release height

- Buffer zones

Use spray drift 

model to estimate 

deposition/exposure

Use model estimates to 

describe the level of 

confidence in assessment 

conclusions 

(RQ-LOC comparisons)
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Risk Mitigation

Regulatory Decision

 Legal Standards

 Risk Characterization

 Risk Management Tools

 Benefit Analysis

 Public Inputs

FIFRA

ESA

FQPA etc
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Risk Management – Product Labels

• Current labels include:

– Instructions for minimizing drift and may include min/max wind 

speeds and max spray heights

– May include additional restrictions – mean droplet size category, 

no-spray buffer zones

• Use of verified low drift technologies can 

lessen need for application restrictions

• Represents the future of better agricultural 

management practices.
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Example of Risk Management Credit 

for Using DRT Nozzle

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70 80 90 100

Concentration (μg/L)

Distance (ft)

Example of Aquatic Exposure

ASABE-Fine

ASABE-Fine-Medium

DRT Nozzle

LOC for 

restricted use
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Incentives/Benefits of DRT Program

 Standard method for validating and comparing technologies

 Support by equipment and pesticide companies, states, 

researchers

 Fits into our risk assessment/management decision-making

 Reduced off-target drift/deposition – greater protection

 Gives applicators more flexibility, better efficacy, cost savings, 

reduced liabilities

 Moves agriculture sector to develop, sell, use validated low 

drift technologies.
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Reference and Links

Understanding the Science behind EPA’s Pesticide Decisions 

http://www2.epa.gov/pesticide-registration/understanding-science-behind-epas-pesticidedecisions

Generic Verification Protocol for Testing Pesticide Application Spray Drift Reduction 

Technologies for Row and Field Crops

http://www2.epa.gov/reducing-pesticide-drift/epa-verified-and-rated-drift-reductiontechnologies
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Thank you!

Questions/Comments