Published January 28, 2026 · Parkinson's Lawsuit Help
Plaintiffs and their families often want to know what evidence actually exists. This is a working summary of the key human studies on paraquat and Parkinson's disease.
Agricultural Health Study
The Agricultural Health Study, a large prospective cohort of licensed pesticide applicators in Iowa and North Carolina, has reported elevated Parkinson's incidence among applicators with cumulative paraquat exposure. The cohort design — prospective, well-characterized, and large — makes it one of the most credible data sources in occupational neurology.
Tanner et al. case-control studies
Case-control studies led by Caroline Tanner and colleagues have reported odds ratios in the range of 2–3 for Parkinson's disease among individuals with documented paraquat exposure. The effect strengthens with cumulative dose, consistent with a true causal association.
Meta-analyses
Multiple meta-analyses pooling case-control and cohort studies have reported summary effect estimates consistent with a paraquat-Parkinson's association. Effect sizes are larger for higher exposure intensity and longer exposure duration.
Gene-environment interactions
Some studies report stronger paraquat effects in individuals with specific genetic variants in detoxification pathways. Gene-environment interaction does not undermine causation — it explains heterogeneity. Many of the most strongly affected plaintiffs share variants that reduce paraquat clearance.
What this means in court
Causation in toxic tort is general (can paraquat cause Parkinson's?) and specific (did paraquat cause this plaintiff's Parkinson's?). The general-causation evidence is mature. Specific causation turns on exposure documentation, clinical diagnosis, and differential diagnosis — which is why thorough records gathering is essential.
Get a free case review
If you or a family member were exposed to paraquat and have been diagnosed with Parkinson's disease, request a free case review. It takes 15 to 30 minutes by phone, costs nothing, and locks in your place while settlement options remain open. Check eligibility or call (717) 724-7503.