Exposure to pesticides at home or in gardens doubles the risk of developing Parkinson's disease, according to a study of almost 500 people diagnosed with the disease. It is the first study to show a significant association between use of pesticide in households and Parkinson's disease. The researchers questioned 496 people diagnosed with Parkinson's disease about past use of pesticides. Each patient was asked if they had used or been exposed to insecticides, herbicides, fungicides or weed killers at home or in the garden. The patients' histories were then compared with 541 people not affected by the disease for the study.