Ritz BR, Manthripragada AD, Costello S, Lincoln SJ, Farrer MJ, Cockburn M, and Bronstein J (2009): Dopamine Transporter Genetic Variants and Pesticides in Parkinson’s Disease. Environmental Health Perspectives Volume 117. Number 6. June 2009

The investigators enrolled 324 people with newly diagnosed Parkinson’s disease and 334 healthy people, as controls, living in California’s agricultural Central Valley.

The authors were able to identify people who had lived within 500 yards of fields where the pesticides maneb and paraquat had been used at any time during the previous 35 years. Individuals were also interviewed to determine whether they had ever been exposed to pesticides through their jobs. DNA samples were extracted from blood samples or cheek swabs to detect genetic variability in the dopamine transporter gene.

People with one susceptible allele who lived near fields where maneb and paraquat were used had a three-fold increased risk of developing Parkinson’s disease. People who had two or more susceptible genetic variants (alleles) had almost a 5-fold increase in risk. Importantly, people who were genetically susceptible but had no pesticide exposure showed no increased risk. Parkinson’s disease, like many diseases, appears to be caused by a complex interaction of genetic and environmental factors.