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Consideration of Pesticide Spray 

Drift Reduction Technology in EPA 

Ecological Risk Assessments

Faruque Khan

U.S. Environmental Protection Agency

September 20, 2011
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Motivation for this Work

Overall risk reduction, increased sensitivity to spray drift 

issues from suburban development and endangered 

species concerns

Development of improved methods, tools, and data for 

EPA’s risk assessment and risk management for 

registration decisions 

Verifying and quantifying a DRT's potential to reduce drift 

can benefit growers/applicators, manufacturers, public, 

and the environment

The acceptance of a larger variety of DRTs would allow 

greater flexibility in drift management
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Collaborations & Partnerships

U.S. Environmental Protection Agency 

 Office of Pesticide Programs (OPP)

 Environmental Technology Council (ETC)

 Environmental Technology Verification (ETV) Program

U.S. Department of Agriculture (USDA)

Pesticide Manufacturers

Stakeholder Groups include: pesticide registrants, adjuvant 

producers, applicator groups, sprayer manufacturers, 

academic and government researchers

Interest in collaborating with other countries
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Overview of DRT Evaluation

Measure of performance in wind tunnels

 Droplet size distribution

AGDISP model run with measured droplet size 

spectra under a typical condition

Droplet size spectra used to model downwind 

deposition for aquatic and terrestrial 

environments 

Deposition data compared to ASABE S572 

reference spectra
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Low Speed Wind Tunnel (LSWT) test was 

conducted at the EPA’s Aerosol Testing 

Facility (ATF) in Research Triangle Park, NC

High Speed Wind Tunnel (HSWT) test was 

conducted at the USDA-ARS facility in College 

Station, TX

DRT Protocol Verification

Data generation and acquisition were performed 

with a reference and two candidate nozzles for 

the following testing scenarios:
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Spray Nozzles and Material

NOZZLES

Reference Nozzle

 ASABE S572, fine/medium boundary

 110 flat-fan, 43.6 psi, 0.31 gpm

Test Nozzle A

 Teejet AI-11003 VS induction nozzle

 Very coarse spray per ASABE S572

 43.5 psi, 0.3 gpm

Test Nozzle B 

 Hypropumps ULD 120-04 dual air induction nozzle

 Coarse spray per ASABE S572

 43.5 psi, 0.4 gpm

SPRAY MATERIAL

Deionized water with 0.25% v/v of a 90% nonionic surfactant

Uranine tracer at 3.6 g/L
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Comparing nozzles performance relative to a 

reference system

Use the ASABE S572 nozzle/category associated 

with the test DRT atomizer for the reference

Concept of a Spray Drift Reduction Factor:

(Deposition)DRT

(Deposition)reference

Selection of Reference System

= SD Reduction Factor
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High Speed Wind Tunnel Test

Intended for aerial application

Critical measurement was droplet size

 AGDISP spray drift model was used 

to estimate downwind deposition

Other measurements were monitored for 

confirming/understanding DRT 

performance
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Droplet Size Spectra for HSWT
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AGDISP Modeling
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AGDISP Modeling
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Comparison of driftable fractions
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Estimation of Deposition
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Depositions and buffer distances

for aquatic environment
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Depositions and buffer distances

for terrestrial environment
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Buffer Distance Estimations 
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Use of Results

The drift reduction associated with a DRTs use could 

be utilized by EPA to develop spray drift reduction 

factors

Spray drift reduction factors could be incorporated 

into EPA pesticide risk assessments:

 Drinking water assessments 

 Aquatic organism assessments

 Terrestrial plant assessments

 Special assessments

Allow more labeling options for pesticide products to 

manage spray drift
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Distance from application site

Amount. of drift and risk

Level of concern 

for a pesticide 

for people, 

animals, plants

Relationship Between Application Technologies, 

Amount of Drift/Risk, and Risk Management

Need for risk management restrictions

No DRT

DRT*

DRT**

DRT ***
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Summary

Verification test results of DRTs provide an opportunity to 

evaluate the performance of the draft protocol

EPA and pesticide manufacturers could include use of 

DRTs in risk assessments and on product labels

A winner for multiple stakeholders:

 Gives greater flexibility and knowledge to growers and 

applicators to meet or improve on drift requirements

 Gives incentives to equipment manufacturers to 

manufacture/sell DRTs

 May lower overall costs of spraying

Opportunity to extend similar efforts for future DRT 

verification program compatible with other countries
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URL Links to EPA’s Spray 

Drift and DRT Project

http://www.epa.gov/pesticides/factsheets

/spraydrift.htm

http://www.epa.gov/etv/este.html#pdrt
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