ALS

Conventional wisdom suggests that occupations associated with low socioeconomic status – such as construction, extraction and maintenance jobs – would be linked to the greatest number of ALS and Parkinson's deaths because of workers' environmental exposures to chemicals. But the CDC found the opposite to be true.
The actor and musician knows how to convey a message that effects medical change, helped in part by his visit top be with sick kids at Children's Hospital Los Angeles. Now, let's see if Hollywood follows suit. 
Since there's no known cause for the majority of ALS cases, any new (even bad) research is widely cited. A new study in JAMA Neurology claims to find a link between five chemical compounds and the disease, but it's just a loose correlation coupled with other confounding data. It all should be taken with a very large grain of salt.