Exposure to high levels of the industrial weed killer paraquat combined with a previous head injury have been identified as a serious combination risk factor increasing a person's chance of developing Parkinson's disease.
According to a report from the Canadian medical site InsiderMedicine.ca, suffering a head injury and being exposed to paraquat tripled a person's chances of developing Parkinson's disease. Each of these factors can stand alone as one that can significantly increase a person's chance of developing Parkinson's disease but a new study appearing in the most recent edition of the journal Neurology found that both those risks combine to raise the chance of Parkinson's even more.