The pesticide occurs naturally in tropical plants such as the jewel vine, and synthetic versions made in the lab are used by organic farmers. It is used as an insecticide and for killing fish in water management schemes. While the study does not prove that Parkinson's in humans is caused by exposure to this chemical, it provides a link between the illness and the environment. No one has shown a direct link between rotenone and Parkinson's before. We do not and cannot claim that rotenone is a cause of Parkinson's in humans, but in rats chronic exposure to it is sufficient to cause all the manifestations.
Many pesticides act in exactly the same way as rotenone.
Additionally, there are similar toxins produced by other plants and fungi to which we might be exposed. The finding lends credence to the idea that long-term exposure to environmental poisons, including pesticides, may make it more likely that Parkinson's will develop. Parkinson's disease is one of the most common neurodegenerative diseases, affecting about one per cent of all people over the age of 65. Symptoms include problems with movement and severe muscle spasms leading to uncontrolled tremors. The brains of Parkinson's patients contain microscopic protein deposits, called Lewy bodies.