Approximately 92% of the land in Iowa, 64% in Indiana, and 27% in Michigan is agricultural farmland. Nearly 77% of farmland in Iowa and Indiana, and 58% of farmland in Michigan, were treated with herbicides in 2012 (USDA). Pesticide drift, or “overspray”, is defined as any off-site movement of pesticide during its application. Exposure to this drift has the potential to damage crops and landscaping, kill aquatic animals, and cause DNA damage, cancer, and allergic wheeze in applicators. The Pesticide Bureau of the Iowa Department of Agricultural and Land Stewardship (IDALS), the Indiana State Chemist (ISC), and the Michigan Department of Agriculture and Rural Development (MDARD) investigate complaints of pesticide misuse, including reports of pesticide drift. Individual narrative reports and case summaries are available, but have not been analyzed to identify contributing factors to prevent field, worker, and community exposures; nor has the community at large been surveyed about reporting practices.
The aim of this research was to (1) identify determinants of pesticide drift events in the Midwest, comparing between states; (2) whether differing state policies were associated with drift characteristics and/or reporting of incidents; and (3) determine the proportion of events that occurred due to applicators ignoring pesticide label guidance. This examination will provide guidance when developing policies and prevention efforts used to minimize the hazards associated with pesticide drift.
Narrative case reports from IDALS and MDARD, and case summaries from ISC spanning 2010-2016 were analyzed. Narratives and case summaries were converted to trackable data for ease of analysis using Excel. Data analysis includes descriptive statistics on continuous variables (e.g., distance, wind speed), chi-square tests, and t-tests. Analysis includes: crop damage associations with wind speed by chemical; ratio of human exposures across aerial applications, and associations of distance to target crop and reported plant damage. Key state policies were compared and the responses from a survey concerning the reporting of drift incidents was analyzed. The proportion of cases that violated weather and distance recommendations/label directions for the five most common pesticides in each were analyzed.
Between 2010 and 2015, Iowa received 471 reported drift cases; between 2011 and 2016 Indiana received 391, and between 2014 and 2016 Michigan received 91 reports. The five most common pesticides analyzed for during drift investigations varied between states, but 2,4-D, glyphosate, and atrazine were common to all states. The method of application, (i.e., aerial or ground), wind speed, and the intended target crop were significantly associated with drift events across all three states. While Iowa was the only state to contain regulatory language concerning drift to bees or livestock, all states still reported 4 to 5% of cases in which pesticides drifted onto animals. Michigan was the only state to suggest the creation and use of a drift management plan and was the only state requiring applicators to inform neighbors of drift. About 30% of confirmed drift cases involved applications within 7.62 meters of desirable vegetation, and about 40% of applications occurred in wind greater than 4.5 m/s. More education, training, and community involvement are suggested interventions to reduce drift cases.