A Better Tool to Quantify Pesticide Risk
February 9, 2024 by IAPPS
By Eleanor Meys
The adverse effects of pesticide use on humans and the environment have long been a concern for consumers, growers, and scientists—and rightly so. In the past, we have seen the catastrophic effects when nontarget risks of pesticides are not known or properly considered.
A classic example in the United States was the use of the insecticide DDT (dichloro-diphenyl-trichloroethane) in the 1940s to 1970s. The use of DDT was detrimental to the reproduction of bald eagles and other raptor and fish-eating birds, contributing to several population declines in the mid-20th century. Unfortunately, the high toxicity of the replacement insecticides—organophosphates and carbamates—to birds also led to additional avian casualties in many farm fields.
At this point, we cannot realistically eliminate the need for all pesticides in most crops, but we can make better decisions about the chemicals we use. Fortunately, for us (and the environment), tools are continuously being developed to better inform the selection of pesticides, not only for efficacy but also to minimize environmental and human health risks.
One such tool is the Environmental Impact Quotient (EIQ), developed and supported by Cornell University. The EIQ uses information about a pesticide’s chemical properties to assign certain numerical classifications to risk categories. The numerical classifications and the amount of a pesticide applied are used to calculate a hazard value. The EIQ is essentially a hazard quotient, as opposed to a true risk quotient. (Hazard refers to something that can cause potential harm, while risk refers to the likelihood such harm will occur.) This approach allows the user to compare the output value for different chemicals to determine which pesticide has the least risk. However, these values are only meaningful when numbers are compared to each other. Although the EIQ has received criticism in the scientific literature, the method has been widely adopted during the past 30 years.
A group of colleagues and I recently reviewed a lesser-known risk quantification tool, the Pesticide Risk Tool (PRT), developed by the IPM Institute in Madison, Wisconsin. The PRT is an online tool that allows users to assess pesticide risk for 15 different human-health and environmental measurement scales, or indices. Some examples of the PRT categories include impacts to birds, earthworms, aquatic algae, human workers, and pollinators. We introduce and explore the Pesticide Risk Tool in an article published in January in the Journal of Integrated Pest Management.
What makes the PRT unique is that it goes further than the classic hazard quotient to develop a true risk quotient. We consider the PRT a true risk quotient because, for several of its environmental indices, it calculates the probability of a nontarget environmental effect occurring from a given pesticide application. This probability is determined by analysis of relevant field studies. For example, the “avian acute” index calculates the probability (between 0 percent and 100 percent) that a chemical application will cause avian mortality. The risk output from the PRT gives the user an understanding of how a pesticide can affect the environment. Users can still compare chemicals, similar to hazard quotients, but comparisons from the PRT are based on the probability of real-world effects instead of arbitrary numbers.
Beyond characterizing real-world risk, the PRT has many other advantages compared to similar tools. The PRT uses scientifically sound methods in its calculations, including either the use of data from field-derived studies, as mentioned above, or the best risk-assessment processes available to date. The PRT’s online tool presents results in both table and graph formats.
Currently, insects that humans rely on to pollinate our crops are threatened, with one threat being pesticide use. A pesticide’s effect on pollinators is a complicated problem due to multiple pathways of pesticide exposure—for example, via direct contact within a field, from drift near the field edges, or through consumption of contaminated pollen and nectar. The PRT considers these different exposure routes and includes three separate indices to quantify pollinator risk: One for pollinators in the area sprayed while a crop is in bloom, another for pollinators in the area sprayed while a crop is not in bloom, and a third for pollinators immediately outside of the area sprayed. Having these separate indices allows for an improved risk profile and subsequent selection of pesticide use to reduce the risk to pollinators throughout the year.
In summary, we believe the PRT to be a successful evolution of risk assessment tools beyond simple hazard quotients such as the EIQ, and it provides more accurate results with greater real-world meaning. The PRT produces more advanced ways to characterize pesticide risk, aiding in formulating safer pesticide regimens and finding solutions to mitigate environmental and human risk. As one example, the PRT model has been tailored and adopted by the Lodi Wine Growers of California as a key element of their LODI RULES Sustainability Certification program, supporting the value of the PRT in documenting sustainable pest management strategies.
With the advantages of the PRT outlined here, we encourage researchers, IPM practitioners, and growers to evaluate the PRT as a new tool for making better pest management decisions when using pesticides.
Journal of Integrated Pest Management
Eleanor Meys is a master’s student and graduate research assistant in crop sciences at the University of Illinois, Urbana-Champaign, who completed her bachelor’s degree in fisheries, wildlife, and conservation biology at the University of Minnesota in 2023. Email: email@example.com.