This Widely Used Pesticide May Raise Your Parkinson’s Risk by Over 2.5 Times

• The chemical’s utility across so many environments led to widespread adoption — At its peak, chlorpyrifos was one of the most heavily used insecticides in the United States, applied through aerial spraying, tractor-mounted systems, and direct soil treatment. Its residues were detected in food, drinking water, household dust, and ambient air, especially near agricultural regions.⁵

• Restrictions rolled out slowly and inconsistently — In the late 1990s, routine environmental monitoring had begun to reveal how far and how persistently chlorpyrifos could spread. Although the U.S. Environmental Protection Agency (EPA) began restricting residential uses of chlorpyrifos in 2001, agricultural applications continued for decades.

In 2021, the EPA issued a final rule revoking all food crop tolerances, effectively banning chlorpyrifos use on food. However, that decision was overturned in November 2023 by the U.S. Court of Appeals, which ruled that the EPA had not sufficiently justified the revocation. As a result, food tolerances were reinstated in December 2023, and chlorpyrifos is once again legally permitted on food crops in the U.S. unless further regulatory action is taken.⁶

• You can be exposed to chlorpyrifos in several ways — Inhalation is the most common route, as the chemical becomes airborne during spraying and drifts into nearby homes. Food is another source, since residues often remain on produce even after washing. Chlorpyrifos also enters drinking water through runoff. Farmworkers and their families experience far higher levels due to close contact.⁷

• The same mechanism that kills insects threatens human health — Chlorpyrifos blocks an enzyme that regulates communication between nerve cells. When that enzyme is inhibited, the nervous system cannot transmit normal signals. This is how the insecticide kills pests, but the problem is that this mechanism does not distinguish between insects and other forms of life.⁸

• Long-term residential exposure tied to sharply higher Parkinson’s risk — Individuals with sustained exposure to chlorpyrifos experienced more than a 2.5-fold increase in Parkinson’s disease risk compared to unexposed individuals. The strongest associations appeared when exposure occurred 10 to 20 years before diagnosis. This long latency period reflects how Parkinson’s develops silently.

• Animal models reproduced Parkinson’s-like motor impairment — To test biological relevance, researchers exposed mice to chlorpyrifos at levels designed to reflect human inhalation exposure. After 11 weeks, exposed mice developed measurable motor deficits, including reduced performance on coordination and strength tasks. These impairments persisted after a washout period, indicating underlying neurological damage rather than temporary toxicity.

• Selective loss of dopamine-producing neurons mirrored human disease — When researchers examined the mice’s brains, they found that chlorpyrifos had destroyed about one-quarter of the dopamine-producing neurons in the substantia nigra, the exact brain region that degenerates in human Parkinson’s patients. Meanwhile, nearby dopaminergic regions remained largely intact.

This selective pattern matched human Parkinson’s pathology rather than generalized neurotoxicity, strengthening the disease-specific link. Dopamine-producing neurons control movement, motivation, and reward, which explains why their loss causes the tremors, stiffness, and slowness that define Parkinson’s disease.

• The study also found abnormal buildup of a protein called alpha-synuclein — This protein normally helps nerve cells communicate, but in Parkinson’s disease, it becomes altered and begins to accumulate in harmful forms. The affected brain cells also showed signs that their waste removal system wasn’t working properly, making it harder to clear out these damaging protein clumps.

• Autophagy disruption emerged as a central mechanism — To understand why these proteins accumulated, the researchers examined cellular waste-processing systems responsible for clearing damaged proteins. They found that key markers of autophagy, the cell’s primary recycling pathway, were reduced within dopaminergic neurons following chlorpyrifos exposure.

• Low-dose experiments reinforced autophagy as the weak point — Even at low exposure levels, chlorpyrifos caused selective loss of dopaminergic and other aminergic neurons while nearby sensory neurons remained unaffected. When researchers genetically disrupted autophagy-related proteins, the same pattern of neuron loss appeared without chlorpyrifos, tying neuronal vulnerability directly to impaired cellular cleanup rather than the pesticide alone.

• The study also examined microglial activation — This refers to changes in the brain’s resident immune cells when they sense damage or stress. These cells shifted into an activated state, showing physical changes that signal an ongoing inflammatory response in the brain.

However, limiting this immune activation did not stop nerve cells from being lost, indicating that inflammation occurred alongside the damage rather than being the main cause of it.

• Neurodevelopmental delays and cognitive impairment — Prenatal and early-life exposure to chlorpyrifos has been associated with measurable impacts on children’s brain development. Studies that followed birth cohorts found that higher levels of chlorpyrifos biomarkers in umbilical cord blood predicted lower IQ scores, slower motor skills, and structural differences in brain imaging later in childhood. These differences reflect altered neural development rather than short-term effects.¹⁰

• Attention and behavior disorders — Children with detectable chlorpyrifos exposure during pregnancy or early childhood have shown higher rates of attention problems and behaviors consistent with attention deficit disorders. These associations appear in multiple cohort studies that measured exposure levels and tracked behavioral outcomes over time.¹¹

• Reduced birth weight and impaired physical growth — Higher chlorpyrifos levels in cord plasma have been linked with lower birth weight and shorter length at birth in epidemiological research. These findings suggest that even low-level environmental exposure during pregnancy can influence physical development markers at birth.¹²

• Respiratory disease and lung function impairment — Farmworkers and children living in agricultural communities experience higher rates of asthma, wheezing, and reduced lung capacity linked to organophosphate pesticide exposure.¹³

• Endocrine disruption and thyroid problems — Chlorpyrifos and some of the chemicals can interfere with hormonal signaling by binding to estrogen receptors and disrupting enzymes involved in growth, development, and metabolism.^14,15

Early-life exposure to chlorpyrifos has also been shown to interfere with thyroid hormone signaling in the liver, leading to low thyroid activity and disrupted blood sugar control. In animal studies, this disruption caused the liver to keep producing glucose even when insulin was present, resulting in chronically elevated blood sugar.¹⁶

• Reduced fertility — A systematic review and meta-analysis of organophosphate pesticide exposure reported associations with semen quality parameters and male reproductive hormones across available human case-control evidence, placing chlorpyrifos within a class of exposures repeatedly examined for reproductive effects.¹⁷

• Acute organophosphate poisoning — At high doses, chlorpyrifos can cause symptoms such as muscle twitching, sweating, vomiting, respiratory distress, and seizures. These effects have been documented in cases of occupational exposure and pesticide accidents, requiring hospitalization and, in severe cases, resulting in death.¹⁸

1. Choose organic whenever possible — Pesticide residues are most concentrated on conventionally grown fruits and vegetables. Choosing organic versions of heavily sprayed produce — like strawberries, spinach, kale, apples, and grapes — can significantly lower your intake. Refer to the Environmental Working Group’s (EWG) annual “Dirty Dozen” list for guidance.¹⁹

If buying organic isn’t always possible, washing produce in a baking soda solution and peeling the skins when appropriate can help remove more residue from the surface.

2. Sweat regularly to support detoxification and brain health — Your skin is one of your body’s primary detox pathways, and sweating helps eliminate stored pesticide residues.²⁰ Activities like walking, strength training, or cycling promote circulation and toxin release. Regular sauna use enhances this effect, increasing the excretion of organophosphates through sweat.

Beyond detoxification, physical activity activates dopamine signaling and supports brain plasticity, which are keys to protecting against Parkinson’s-related cognitive decline.

3. Filter your water — If you’re drinking unfiltered tap water, especially in areas near farms, golf courses, or public parks, you’re likely taking in small amounts of pesticides like glyphosate along with fluoride, chlorine, and heavy metals. Installing a high-quality filtration system removes these hidden exposures.

4. Improve your indoor air quality — Pesticides aren’t just in the foods you eat. They’re also in the air you breathe, drifting into your home and landing on surfaces. Using a HEPA air purifier helps capture airborne particles, and frequent cleaning with nontoxic products reduces buildup. If you live near active farmland or landscaping operations, keeping windows closed during spraying hours also lowers your risk of inhaling chemical particles.

5. Protect your sleep to support neurological repair — Deep, uninterrupted sleep is essential for your brain to clear waste and protect dopamine-producing cells. Even mild sleep disruption interferes with this cleanup process, increasing vulnerability over time. Make your bedroom dark, cool, and quiet.

Stay off screens in the hour before bed and keep a consistent schedule throughout the week. If you wake often or feel unrefreshed, that’s a signal your brain’s cleanup system is falling behind. Prioritizing sleep directly strengthens your brain’s natural defenses against environmental stressors and slows neurological decline.