Environmental factors for decades have been suspected of causing Parkinson's. Scientists have been looking at trying to identify specific environmental toxins we would potentially be exposed to that we can directly link to somebody's Parkinson's. That's proven to be extraordinarily difficult.
For anyone who comes into the clinic, yes, when you hear these stories.... I had a military personnel come to see me. His job for 40 years in the military was to spray pesticides into buildings to get rid of all the different bugs in the building. It really made you think that it's probably what might have triggered his Parkinson's. Is there a way to prove that? The answer is no.
Doing epidemiological studies to identify these links has proven to be extremely difficult. The biggest one, and I think there are still court cases in the United States, is manganese exposure among manganese miners. It looked as if manganese was causing Parkinson's in all of these individuals, and there were big lawsuits and everything. Then it turned out that maybe the epidemiology wasn't as exact as they thought, and maybe the link was not as strong as we thought.
For the individual person, it's very difficult. Yes, there is probably some environmental exposure that somebody's had that might have triggered the process or contributed to the process. But is that the sole cause? Probably not. It's turning into a very difficult thing to study.