Prevention of Occupational Exposure to Pesticide Drift


Pesticide drift is a long-standing issue in the Pacific Northwest, especially for the tree fruit industry and workforce. Studies have shown that at least 60% of drift events were linked to wind speed or direction changes. Understanding the role winds play in pesticide drift can prevent unintended exposure for workers and nearby communities.

Project Overview

This project aims to minimize the causes of pesticide drift exposure. To accomplish this, we sought to determine how factors such as wind speed and direction affected the likelihood of drift events. Our goal was to develop a statistical model and conduct field studies to validate this model for use in forecasting. This model will assist orchardists to assess risks for conditions when drift is most likely to occur.

Findings to Date

  • Linking 2000-2015 data for drift events and weather in Washington (Source):
    • Most pesticide drift events occurred in tree fruit (151/252 = 60%)
    • Drift events primarily occurred during two types of pesticide application: ground spraying (68%) and aerial spraying (23%)
    • Cases of human illness included 69% workers and 31% bystanders
    • Significant wind speed increases or direction changes during applications were found in 56% (32/57) of confirmed drift events with spray records
    • Applicator-recorded wind speed, on average, was 2 mph lower than the nearest weather station
  • Compared to conventional airblast sprayers, tower sprayers produced less pesticide drift and lower worker exposure (Source).
  • An in-depth analysis of five weather stations in the Lower Yakima Valley demonstrated that wind conditions can vary greatly in a small region and that wind can reliably be forecasted up to 6 hours in advance.

Other Accomplishments

  • Established a new approach to study pesticide drift using epidemiological data about pesticide drift illnesses and historical weather data.
  • Supported Yoni Rodriguez as he completed his Master's project in 2022: “Exploring Wind Ramping as a Determinant of Pesticide Drift.”
  • Recommendations to WA Department of Health to increase pesticide illness monitoring and share resources in regions where cases are high during March–July. Staff were trained to link weather data to pesticide illness data and integrate spatial features from GoogleEarthPro into their epidemiological investigations. New standard operating procedures are being developed.
  • Integrated experimental wind alerts into a ‘smart orchard’ and an AgWeatherNet station. We connected with several new agricultural technology startup companies in the tree fruit sector (e.g. Thingy, LLC; Innov8; Harvust) that are using sensors and mobile technology networks to inform precision agriculture and decision support.
  • Developed new training content and recommendations for pesticide training led by the WA State Department of Agriculture and Washington State University.
  • Ongoing member of the Washington’s Pesticide Application Safety Committee (PASCO).

Next Steps

Our results provide actionable information about drift events in terms of time, space, and wind variability. Messages about exposure prevention can be delivered to managers, supervisors, and workers. We have drafted a second paper on the utility of on-site meteorological stations for applicators to monitor wind conditions throughout a spray period, instead of using a hand-held anemometer only at the beginning of a spray period, as is currently required. In the coming year we are coordinating with PNASH’s other pesticide project teams to co-present our results regionally and to disseminate findings through PNASH’s pesticide safety partnerships and media outlets.


Integrated modules into WSDA Technical Service and Education Program and WSU Pesticide Education Program: On Farm Assistance, and Spray Drift Surveillance at Pesticide Technical Assistance and Education | Washington State Department of Agriculture

Pesticide Safety Solutions PNASH Online On-Demand Courses | Pacific Northwest Agricultural Safety and Health Center (

Findings as reported at the end of year five are included in our annual report.


Principal Investigators:

Edward Kasner, PhD, MPH
Assistant Teaching Professor
Environmental and Occupational Health Sciences
University of Washington

NIOSH 2016-2022


Partners and Advisories:
Washington State Department of Health
Washington State University, AgWeatherNet Program


Rodriguez Y. Exploring Wind Ramping as a Determinant of Pesticide Drift. 2022 Master’s Thesis. Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington. ResearchWorks.

Kasner EJ, Prado J, Yost MG, Fenske RA. Examining the role of wind in human illness due to pesticide drift in Washington state, 2000–2015. Environmental Health. 2021 Mar 15;20(1):26.

Kasner EJ, Fenske RA, Hoheisel GA, Galvin K, Blanco MN, Seto EYW, Yost MG. Spray Drift from Three Airblast Sprayer Technologies in a Modern Orchard Work Environment. Annals of Work Exposures and Health. 2020 Jan 1;64(1) 25-37.

Kasner EJ, Fenske RA, Hoheisel GA, Galvin K, Blanco MN, Seto EYW, Yost MG. Spray Drift from a Conventional Axial Fan Airblast Sprayer in a Modern Orchard Work Environment. Annals of Work Exposures and Health. 2018 Nov 12;62(9) 1134-1146.

Prado JB, Mulay PR, Kasner EJ, Bojes HK, Calvert GM. Acute Pesticide-Related Illness Among Farmworkers: Barriers to Reporting to Public Health Authorities. Journal of Agromedicine. 2017;22(4) 395-405.