[QUOTE=parkinsons here-now

the hypothesis of a Parkinson's "cluster", as 4 of the 125 team members developed the disease relatively young.
[/QUOTE]

I don't think the evidence for this is convincing.

Many people search for clusters, not just for frequency of PD but frequency of cancer or many other things.

Almost always selected clusters showing a relatively high frequency of PD (or cancer or whatever) are what are called Type 1 statistical errors; seeing a pattern when there is just random noise.