Chronic exposure to the pesticide rotenone can produce parkinsonian like symptoms in animals, leading scientists to believe that it may do the same in humans.
This investigation had some grounding in human experience. In the 1980s, a number of heroin users developed irreversible symptoms of Parkinson's after injecting themselves with a batch of MPTP contaminated heroin.
MPTP acts in a similar way to rotenone it inhibits complex I (the NADH de-hydrogenase complex), an enzyme involved in the development of Parkinson's.
More study is needed, but the researchers note that, within 24 hours of the study results being made public, they were contacted by two Parkinson's patients who had also been exposed to rotenone on a regular basis (Lancet, 2000; 356; 1659).