One more reason someone has PD
 

The Hidden Toll of Traffic Jams

Scientists Increasingly Link Vehicle Exhaust With Brain-Cell Damage, Higher Rates of Autism

Wall Street Journal, November 8, 2011

Children in areas affected by high levels of emissions, on average, scored more poorly on intelligence tests and were more prone to depression, anxiety and attention problems than children growing up in cleaner air, separate research teams in New York, Boston, Beijing, and Krakow, Poland, found. And older men and women long exposed to higher levels of traffic-related particles and ozone had memory and reasoning problems that effectively added five years to their mental age, other university researchers in Boston reported this year. The emissions may also heighten the risk of Alzheimer's disease and speed the effects of Parkinson's disease.

Traffic fumes
 

Hi Digger,
Yes, I travelled by car 50 miles each way to work, for 5 years, 1980 to 1985.
So I was doing 100 miles every day for 5 years, just to work!!
Add to this all the social and holiday miles, and lived in my car.
I was diagnosed with PD just 6 years after leaving the 100 miles per day job. I then did 50 miles per day to work for 10 years,
I often thought about the fumes on the 100 miles per day job, and wondered what harm I was doing to myself. Now I know. This trip was mainly along a notoriously busy motorway,(interstate) road. There was a deep valley, known locally as "Death Valley," due to the fact that it was always shrouded in a dense fog of traffic fumes. All 6 lanes were affected, and there was an accident there daily as I went through it.

Ron