This. (Warning: light-weight argument incoming, but it’s intriguing) Is anyone seriously looking into this? How do we know that (for example) subway workers don’t have shorter lifespans that can’t be accounted for any other way? Just taking a superficial, devils-advocate stance makes me wonder what other broad correlations may exist that aren’t known just because they’re not being investigated rigorously? In some ways this also intersects with the bias against publishing negative results - what if a good study of this has been done but wasn’t published because it wasn’t headline-grabbing?