A hypothesis paper published in the Journal of Parkinson's Disease argues that trichloroethylene (TCE), a century-old industrial chemical found in contaminated groundwater and buildings across the US, may be a major overlooked driver of Parkinson's disease — with epidemiological evidence showing exposed individuals face 500% increased risk. Lab studies show TCE damages dopamine-producing neurons, and real-world examples like Camp Lejeune (70% elevated risk) and a Rochester law office cluster support the connection. The challenge is that Parkinson's typically emerges decades after exposure, making the link hard to trace, and most exposure occurs unknowingly through drinking water, groundwater vapors rising into buildings, and indoor air rather than occupational settings. Researchers call for faster cleanup of contaminated sites and expanded vapor mitigation systems similar to radon testing, but thousands of polluted sites remain across the country.