MINNEAPOLIS — Air pollution continues to be a global health risk. Now, a new study is linking the most polluted areas in the United States to an incurable neurological disease. Researchers working with the American Academy of Neurology say a “hot spot” for air pollution in the U.S. shows a link to higher rates of Parkinson’s disease for people who live there.

Brittany Krzyzanowski, PhD, of the Barrow Neurological Institute and her team included data from 22.5 million people enrolled in Medicare in 2009. Over 80,000 people from this group had Parkinson’s disease. The team then used geographical mapping to pinpoint where the participants lived around the country and calculated rates of disease onset in the different areas.

Study authors calculated the average air pollution exposure levels for study participants using ZIP codes and the counties where they lived. They were specifically looking at concentrations of fine particulate matter (PM 2.5), in these areas. These particles often come from car vehicle exhaust, power plant fuel burning, and other industrial products. To do this, they referenced air pollution data sources in order to note average yearly concentrations of this harmful material.

Finally, the team divided participants into four groups based on average exposure. They found that in the highest exposure group, there were 434 new Parkinson’s disease cases for every 100,000 people, compared to 359 cases in the group with the lowest exposure. After adjusting for other possibly confounding factors that could affect Parkinson’s risk, the results remained consistent. Those in the highest air pollution exposure group had a 25-percent increased risk of developing Parkinson’s compared to those in the lowest tier.

Where is America’s air pollution hot spot?

“We used geographic methods to examine the rates of Parkinson’s disease across the United States and compared those rates to regional levels of air pollution,” explains Krzyzanowski in a media release. “We found a nationwide association between Parkinson’s disease and air pollution exposure, with people exposed to the highest levels of fine particulate matter having an increased risk of Parkinson’s disease compared to people exposed to the lowest levels. We also identified a Parkinson’s disease hot spot in the Mississippi-Ohio River Valley, which is a region that has some of the highest levels of fine particulate matter pollution in the nation.”

Interestingly, the researchers found the strongest link in the Rocky Mountain region, which is southwest of Denver and its local counties. In this region, Parkinson’s disease increased by 16 percent when residents moved from one level of air pollution exposure to the next.

“By mapping nationwide levels of Parkinson’s disease and linking them to air pollution, we hope to create a greater understanding of the regional risks and inspire leaders to take steps to lower risk of disease by reducing levels of air pollution,” Krzyzanowski concludes.

Krzyzanowski’s team is presenting their findings at the American Academy of Neurology’s 75th Annual Meeting.