Wow, John! That is impressive and rather, I daresay, pretty. You have created an aurora borealis of PD

It is very striking to see that the Wilis study challenges the long held and widely disseminated assertion that rural living or working in a rural environment increases the likelihood for PD. The map clearly shows the opposite. What I find really alarming is the Great Lakes "trail"- that is not just Midwestern US but more a huge sweeping arc along the states bordering Lake Erie extending into the Northeast; I wonder if this prevalence extends across the Canadian borders?

I was also surprised to see in vastly green areas pockets of PD or clusters show. IMHO, it is easy to surmise that in urban areas, air pollution is the likely culprit. That suffices if we want to say that many things cause PD and leave room for agricultural use of pesticides. My next question is do the clusters in the South and West US reflect areas of high pesticide use or runoff. Next question is pesticide sprayed in those areas? I think for all of us the likelihood that the toxins are airborne is a pretty safe bet.

My bet on yielding answers has always been on the small groups where the odds are really rare. To that end, I ran across a study in Canada of three clusters. Overwhelmingly they all support how much our immediate environments play a part, more so than air quality outdoors. Is it the air quality inside buildings that counts? These clusters support this theory. All people who developed PD in these cases shared common work space; a poorly ventilated tv studio, a garment manufacturing facility, and a portable classroom over a filled in waste dump. BTW, I think that first group included MJF.

There is an even bigger takeaway here. From the Canadian researchers:

Furthermore, familial occurrence does not necessarily mean genetic causation, because family members share their environment and their genes. One study demonstrated that the risk for development of PD in a child from a parent-child cluster depended on the child's age when the parent started to show symptoms rather than the parent's age; younger children had greater risks. This finding suggests environmental risk factors.

John, these researchers toy with answering your question from awhile ago. If we remain in the environment that triggered PD are we doing further harm? Their conclusion surprised me:

[B]This pattern suggests an environmental cause that exerts its influence during a short time during the period of the shared environment and results in a cascade of events culminating in the clinical manifestations of PD after a long delay.[/B] One study15 used a mathematical model based on observations relating to clinical deficits to indicate the most likely pathogenesis is an event that kills some neurons and damages others in such a way that their life expectation is reduced, or an event that triggers a mechanism that kills healthy neurons at a constant rate. These models best explain the occurrence of PD clusters such as ours.

Clustering of Parkinson Disease: Shared Cause or Coincidence?
JAMA Network. 2004.

It also looks like latency of exposure period might yield some valuable clues. The TV crew was the youngest onset and had the shortest latency to PD of 9 years. High levels of Carbon Dioxide were found in air samples.

This makes me even more curious about those pockets of red on the US map and I am sure you have a correlate on yours.

Laura