Lerch,

Thank you for your reply. You don't mention a state in your location data; health care varies from state to state, so such can be relivent.

regarding your remarks: The 'outdoors' party of your remarks may play well with statistics . . . but the chemical part has faired poorly in epidemiology studies . . . in amyotrophic lateral sclerosis one might think of the Guam epidemiology study associating flying fox and cycads containing β-Methylamino-L-alanine:

Lytico-bodig
Lytico-bodig disease - Wikipedia
ALS-like disorders of the Western Pacific
ALS-like disorders of the Western Pacific

doubt was raised by the observation neither the flying fox nor the cycada trees exist in the Kii area of Japan.

The chemical exposure hypothesis has lenghy history with research involving the disorder but tends to produce problematic paradoxes regardless of the plausible poison; those persisting in this line of thought often wind up trying to leverage complexity theory through combinatorics. I kinda doubt the simple single chemical exposure hypotheses can carry the day because where any of them true, discovery ought to be achieved by now. Natural poisons have long existed, as has amyotrophic lateral sclerosis but artificial poisons are not available 'before chemestry.'