Researchers at the University of Iowa have found several pesticides commonly used on farms are showing up in surface water, urban canopies and even household dust. They say their results provide new insights into how this large and diverse group of chemicals travel through Iowa’s environment.
‘Pesticide’ is an umbrella term that includes insecticides, herbicides, fungicides and other -cides intended to control pests. They’re used heavily in farm country.
After California, Florida and Illinois, Iowa ranks fourth in the U.S. for pesticide usage by weight, according to the latest U.S. Geological Survey estimates.
The U.S. Environmental Protection Agency is required by federal law to balance the benefits of a pesticide with the potential risks to human health and the environment when deciding whether to approve it. However, science is always evolving.
A growing body of research suggests exposure to certain pesticides increases risks for adverse health outcomes, including cancer, neurological disorders and hormone disruptions.
Researchers like Darrin Thompson are trying to better understand the complex relationships between pesticides and human health in Iowa.
“It's all kind of a gradual, systematic process of trying to understand what's in the environment, what are we as Iowans potentially being exposed to, and then ultimately what does that mean for our health,” Thompson said.
The environmental epidemiologist also serves as the associate director of the Center for Health Effects of Environmental Contamination (CHEEC) at the University of Iowa. This summer, CHEEC and IIHR Hydroscience and Engineering launched Iowa Integrated Network for Science, Information and Geospatial Health Tracking (INSIGHT.)
The five-year initiative includes developing new methods to detect widely used pesticides in Iowa, working with partners to expand monitoring and improving techniques to measure human pesticide exposure using blood, urine and other biological samples.
Thompson said the latest findings from INSIGHT build on other research, indicating pesticides are “ubiquitous in the environment” and often show up as chemical cocktails.
Pesticides found in water, air and dust
The researchers analyzed 193 surface water samples collected between 2024 and 2026 from rivers and streams across northeastern Iowa.
Two insecticides — clothianidin and imidacloprid — showed up in 98% and 82% of the samples, respectively. Concentrations of these insecticides frequently exceeded thresholds set by the EPA to protect aquatic life.
The researchers also detected atrazine, an herbicide used heavily with corn production, in 91% of the 98 samples analyzed in 2025 and 2026. Atrazine is a well-known endocrine disruptor and was reclassified as “probably carcinogenic to humans” last year by the International Agency for Research on Cancer.
To trace the movement of pesticides in the air and evaluate pesticide drift, the researchers collected leaf samples from public parks and elementary schools in Iowa City between May and August 2026.
They found pesticides on almost all leaf samples and a pattern matching the typical application timelines in farm fields. Concentrations of herbicides like atrazine and metolachlor were highest in early summer while fungicides were more prevalent later in the growing season.
The researchers’ pilot study with 28 rural and urban households across Iowa also revealed pesticides from indoor dust samples. The researchers found fungicide azoxystrobin in 80% of the samples and the insecticide imidacloprid in 79%. Tebuconazole, metolachlor and atrazine were present in 57%, 37% and 32% of the samples, respectively.
“When we talk about pesticides, the assumption is that the people who are going to be most exposed or most at risk are going to be the ones who are actively applying, which is true to an extent,” Thompson said.
But the researchers’ latest results suggest Iowans may be exposed through other means.
Iowa INSIGHT will continue monitoring pesticides and plans to develop methods to test for the herbicide glyphosate.
“We still have a lot of work to do, but understanding that [pesticides are] there and understanding how we're potentially exposed to them is an important step,” Thompson said.
