Oh, there's no doubt that over exposure to chemicals (and everyone's "safe" exposure level is unique to that person) can cause merry hell on the body, and that can manifest itself in many different ways.
But, again, we can look at physical causes for me. My back is an obvious one because of the fall and following "brute" work on construction sites. My hands and wrists? I can look at years of using hammer drills and Kangos having a detrimental effect as well as the brute force work (cable pulling, heavy weights, etc). Hips and knees? Working on construction sites.
Basically, things are worn out.