Researchers Studying Whether Pesticide Exposure Affects Farmworkers’ Brain Health

With the skyline of downtown Oxnard in the background, farmworkers gather plastic that is used in strawberry fields to contain pesticides. Photo: Hannah Guzik.
With the skyline of downtown Oxnard in the background, farmworkers gather plastic that is used in strawberry fields to contain pesticides. Photos: Hannah Hough.

On her way to her office in Oxnard, Rachel Casas drives past farmworkers bent over in the fields. Because she is a neuropsychologist, she wonders whether there are pesticides in those fields and if the chemicals may be affecting the laborers.

She still doesn’t know the answer to that question, but she and two other Cal Lutheran University researchers are getting closer to finding out.

The interdisciplinary team of researchers wants to know if there’s a link between pesticide exposure and decreased brain health. Previous research suggests there is an association, but the kinds of tests Casas is conducting — the same ones used to assess cognitive function in clinical patients — haven’t been done to this extent before on farmworkers, she said.

The researchers are testing the urine of about 150 farmworkers in Oxnard for markers of pesticides and then giving memory tests, puzzles, and thinking games to the same group. One of the state’s agricultural hubs, the Oxnard Plain produces about 20 percent of California’s strawberries, often one of the most pesticide-laden crops.

“This is an issue that’s important to everybody, because it’s about what we’re all exposed to on a daily basis,” said Casas, assistant professor of graduate psychology at the university. “It’s meaningful work, and I can see that it’s meaningful work just by virtue of where my office is and where I live.”

Studying exposure

In the first part of the study, completed late last year, Grady Hanrahan, a chemistry professor at the university, found that farmworkers have more markers of pesticide exposure in their urine than others who live within a half-mile radius of farms or further away. The technology Hanrahan used to test the urine — gas chromatography and mass spectrometry — is not able to measure the levels of pesticide exposure, in part because the body begins to process the chemicals immediately. But the technology can detect whether a person has been exposed to a range of pesticides.

“Some are more persistent than others, some are longer lasting,” Hanrahan said. “What I saw was both short-lived and long-lived,” which means some people had been exposed recently and in the past.

There are both short-term and long-term risks from exposure to some pesticides, including cancer, impaired attention span, and slowed motor and information processing, Hanrahan said.

Farmworkers checking a celery crop in a Ventura County field.
Farmworkers checking a celery crop in a Ventura County field.

Little access to health information

Even though they are among those most at risk of pesticide exposure, farmworkers have little information on environmental health. In the first part of the study, political science professor Haco Hoang distributed health surveys to farmworkers and other Oxnard residents. Many expressed concern about pesticide exposure and environmental health, but few had accurate information or a way to acquire it, she found.

Now, Casas is administering cognitive tests to a second group of farmworkers, while Hanrahan tests their urine for pesticide markers. Hoang is continuing to survey farmworkers and other Oxnard residents and is developing a framework to help them get more accurate information, which she believes can be applied to other populations nationwide.

“Whether the community is or isn’t harmfully exposed, they should know that,” Hoang said. “We want to develop a model for environmental justice that can be replicated in any kind of community where there are potentially high barriers to engagement and potentially high risk of health risks. We could have conducted the same kind of study with day laborers or people who work in mining.”

The researchers received $250,000 in grant funding from The California Wellness Foundation to conduct both parts of the study.* The results of the study will be released in December, Casas said.

Questions about the agriculture system 

John Krist, CEO of the Ventura County Farm Bureau, said he’s familiar with the study and is “as interested in anybody in what they find.” Growers in the county adhere to the state’s pesticide regulations, he said.

“The use of pesticides is extremely heavily regulated in California, and there are very stringent requirements on how it can be applied and re-entry requirements, or when you can go back into fields,” Krist said. “It’s intended to be protective of the health and safety of workers as well as that of neighbors who may be living near these fields.”

The study shows that the state’s agriculture system is “broken” and that farmworkers need more workplace protections, said Erik Nicholson, a national vice president of United Farm Workers, a union founded by Cesar Chavez.

“Most farmworkers lack the ability to anonymously find out what specific pesticides they’re being exposed to in the workplace, so they don’t have the ability to ascertain whether they’re being provided adequate protective gear, for example,” he said.

Farmworkers are often afraid that if they speak up or question pesticide usage, they’ll be fired or blacklisted, said Margaret Sawyer, development director of the Mixteco/Indigena Community Organizing Project, a group that serves farmworkers in Oxnard.

“They know that they have stuff on them, and they’re afraid of ‘what exactly is this stuff and can I trust the company to tell me when I’m being exposed or not?’” she said. “They know that when they come home, if they touch their kids with their long-sleeves from work, the kids start to itch.”

Casas said living and working near fields where pesticides are used has made her research personal.

“I think it’s important from a public health perspective because most people don’t think on a daily basis about the quality of air, soil and water — we don’t think about our exposure to potential environmental pollutants,” she said. “But these are factors that can affect all of us, not just those of us who are farmworkers.”

*Note: The California Wellness Foundation is also a financial sponsor of the California Health Report.

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