The Pesticide-Parkinson's Connection: What Zach Lahn Said on Tucker Carlson and What the Science Actually Shows

When Iowa gubernatorial candidate Zach Lahn appeared on Tucker Carlson's show, he asked a question that made some people uncomfortable: Is there a connection between pesticides and Parkinson's disease? It's the kind of question that immediately gets political, with some people dismissing it as fear-mongering and others treating it as settled fact.

Here's the thing: the science is actually pretty clear. There is a connection. What's less clear is exactly how strong that connection is, which specific chemicals are the worst offenders, and what levels of exposure create meaningful risk. But to pretend there's no link at all? That's just ignoring the research.

Let's look at what we actually know.

The Research on Pesticides and Parkinson's

The connection between agricultural chemical exposure and Parkinson's disease has been studied for decades. A comprehensive 2013 meta-analysis published in Neurology found that pesticide exposure, particularly to herbicides and insecticides, significantly increases Parkinson's risk. The relationship was strongest after long durations of exposure.

More recent research has gotten even more specific. UCLA Health research published in January 2025 found that long-term residential exposure to the pesticide chlorpyrifos is associated with more than a 2.5-fold increased risk of developing Parkinson's. That study analyzed data from 829 people with Parkinson's and 824 without, using California's detailed pesticide use reports to estimate individual exposure over time.

The researchers didn't stop there. They also exposed mice to aerosolized chlorpyrifos using inhalation methods that mimic how humans typically encounter the chemical. The exposed mice showed brain inflammation and abnormal accumulation of alpha-synuclein—a protein that clumps in Parkinson's disease. When they examined how the pesticide damages neurons, they found it disrupts autophagy, the cellular process that clears damaged proteins.

Another UCLA and Harvard study published in Nature Communications in 2023 took a broader approach. Researchers examined exposure history for 288 pesticides among Central Valley patients with Parkinson's. From this screening, they identified 53 pesticides that appeared implicated in Parkinson's—most of which had not been previously studied for a link and are still in use. When they tested the toxicity of these pesticides in dopaminergic neurons (the ones that die in Parkinson's), they confirmed 10 were directly toxic to these critical brain cells.

Specific Chemicals of Concern

Not all pesticides are equally problematic. Research has identified several specific chemicals with particularly strong evidence:

Paraquat: The American Parkinson Disease Association reports mounting evidence that exposure to paraquat can contribute to PD risk. It's already banned in 70 countries due to associations with neurological diseases, but it's still permitted in the U.S. Environmental groups, agricultural worker groups, and Parkinson's advocates recently sued the EPA after it issued an interim re-approval.

Rotenone: A 2025 study in Nature's npj Parkinson's Disease journal showed that the pesticide rotenone triggers lasting alterations in brain gene activity and epigenetic markers. Changes were especially pronounced in the substantia nigra—the brain region most affected in PD. Even weeks after exposure stopped, this "molecular memory" persisted, suggesting environmental toxins may prime the brain for disease years down the road.

Organochlorines and Organophosphates: A family-based case-control study published in Environmental Health Perspectives found that two insecticide classes—organochlorine (mostly DDT and chlordane) and organophosphorus compounds—significantly increased PD risk. Brains from PD patients were found to contain higher levels of organochlorine chemicals than brains from control subjects.

What About Iowa Specifically?

Iowa's situation is particularly concerning because of the state's heavy agricultural chemical use combined with its rising disease rates. Iowa ranks second in the nation for cancer incidence and has the fastest-growing cancer rate, according to the 2024 Iowa Cancer Registry report.

In Palo Alto County in northwest Iowa, the five-year cancer incidence rate is 658.1 per 100,000 people—nearly 50% higher than the national average of 442. Dr. Richard Deming, an oncologist in Des Moines, told reporters: "We have a very high percentage of our land that is growing crops. The current way of growing crops is to use a lot of ag chemicals, which have improved the yield of crops. Is there, potentially, a downside? That's where we really need to do more research."

The National Cancer Institute's Agricultural Health Study has been following about 90,000 farmers and their spouses in Iowa and North Carolina for 30 years to understand cancer risks. Laura Beane Freeman, who grew up on an Iowa farm and is now a principal investigator for the study, notes that farmers generally have elevated rates of prostate cancer. A 2023 study showed farmers with a genetic predisposition for prostate cancer may have even higher risk when exposed to certain pesticides. Another study found that among 53,000 male farmers, those who used the fungicide metalaxyl developed thyroid cancer at twice the rate of those who didn't.

The Nitrate Problem

It's not just pesticides. Iowa's heavy fertilizer use creates water contamination that's also linked to cancer. According to research at the University of Iowa, a 2018 review of 30 academic studies showed a link between ingesting nitrate from drinking water and colorectal cancer. Other University of Iowa studies show nitrate consumption may cause bladder and ovarian cancer in older women.

The connection is "fairly substantial" for colorectal cancer, according to Brandi Janssen, a clinical associate professor in the Department of Occupational and Environmental Health at the University of Iowa College of Public Health. Colorectal cancer is one of the most common cancers in Iowa.

According to environmental researchers, nitrate is an agricultural byproduct: ammonia in natural and synthetic fertilizer is converted by soil bacteria into highly water-soluble nitrate. If over-applied, nitrate leaks into aquifers and contaminates water systems. In Iowa, where 109 billion pounds of factory farm manure are produced annually, the scale of nutrient loading is massive.

The Complexity Problem

Here's what makes this difficult: we're not dealing with single exposures to single chemicals. Real-world agricultural exposure involves multiple pesticides at once, applied repeatedly over decades, combined with other environmental factors like nitrate in water, radon gas, and air pollution from livestock facilities.

As Dr. Janssen explains: "We like stories that are straightforward. One thing causes another, and unfortunately, that's just not the way it works in cancer. It's not the way it works in environmental health. We have multiple exposures that can cause multiple different types of health outcomes."

Scientists still can't define a clear "safe threshold" for pesticide exposure. Both high-dose and long-term low-dose exposures appear risky. Individual differences in age, genetics, occupation, and lifestyle factors like diet and exercise may modify risk, but exactly how remains uncertain.

What This Means for Farmers and Landowners

If you're farming in Iowa or own agricultural land, this research doesn't mean you should panic. But it does mean you should pay attention. Pesticide exposure can happen through occupational handling, environmental exposure from living near agricultural land, and household use of lawn and garden products. A 2025 study in JAMA found that people living 1-3 miles from golf courses had higher Parkinson's risk, suggesting that indirect exposure through air, soil, or water can also play a role.

What can you do? The most obvious answer is to minimize unnecessary chemical use. That doesn't mean abandoning modern agriculture—it means being strategic about applications, using integrated pest management, and considering alternatives where practical.

This is where native prairie systems come back into the picture. Prairie strips and native plantings don't require chemical inputs. They filter water instead of contaminating it. They build soil health instead of depleting it. And they create wildlife habitat in the process. For farmers dealing with marginal ground, areas prone to erosion, or waterways that need protection, establishing native prairie isn't just good for conservation—it's a way to reduce chemical exposure risk while improving land function.

At Hoksey Native Seeds, we work with landowners to establish Iowa ecotype native prairie mixes specifically suited to their region and soil types. These aren't ornamental gardens—they're functional plantings that can serve as buffer strips, provide wildlife habitat, stabilize soils, and reduce the need for chemical inputs on parts of your operation.

The Bottom Line

So was Zach Lahn right when he brought up the pesticide-Parkinson's connection on Tucker Carlson? Yes. The scientific evidence supports a link. That doesn't mean every farmer will develop Parkinson's, or that agricultural chemicals are the only cause. But pretending there's no connection ignores decades of research from reputable institutions.

The bigger question is what we do with this information. Iowa can continue on its current trajectory—pushing maximum yields through maximum chemical inputs, accepting the health and environmental costs as the price of production. Or we can start asking harder questions about whether there are better ways to farm that don't require poisoning the water supply and exposing rural communities to chemicals linked to neurological diseases and cancer.

Those aren't easy questions, and they don't have simple answers. But they're questions worth asking. Especially when you look at the cancer rates in places like Palo Alto County and realize that something is clearly going wrong.

The research is clear: pesticide exposure increases disease risk. What's less clear is whether Iowa is willing to do anything about it. Given that nearly 15% of Iowa legislators are farmers and college sports arenas are sponsored by fertilizer companies, don't hold your breath for major policy changes. But individual farmers and landowners can make different choices about how they manage their land. Those choices add up.

If you're looking for ways to reduce chemical dependency on your operation while improving soil health and water quality, prairie restoration is one tool in the toolbox. It's not the whole solution, but it's a start toward an agricultural system that doesn't come with the same health risks. And in a state with Iowa's cancer rates, that's worth considering.