People who live in large cities or near industrial areas are often exposed to high levels of particulate matter – a mixture of solid particles and liquid droplets in air pollution that forms fine inhalable particles with diameters typically 2.5 micrograms (PM2.5) or less. A recent study found that high exposure to PM2.5 increases the risk of developing Parkinson’s disease by nearly 20 percent.

Researchers conducted a population-based study of more than 21 million older adults living in the US. They assessed their exposure to particulate matter based on their geographical location and ascertained whether they had Parkinson’s disease based on Medicare records.

They found that people exposed to the median PM2.5 level were 56 percent more likely to develop Parkinson’s than those with the lowest PM2.5 exposures. For every additional microgram per cubic meter of PM2.5 exposure, risk increased by 4.2 percent. In the Mississippi-Ohio River Valley, where particulate matter levels are high, the risk of developing Parkinson’s disease was 19 percent greater than in the rest of the country.

These findings suggest that exposure to particulate matter markedly increases a person’s risk of developing Parkinson’s disease, aligning with other evidence pointing to the disease’s environmental origins. Parkinson’s disease is a neurodegenerative disorder that affects the central nervous system. Caused by the destruction of nerve cells in the part of the brain called the substantia nigra, it typically manifests later in life and is characterized by tremors and a shuffling gait. Learn more about Parkinson’s disease and therapies in this episode featuring Dr. Giselle Petzinger.