A Cambridge-led systematic review and meta-analysis found that long-term exposure to PM2.5 and PM10 was associated with a higher incidence of Parkinson’s disease. Across 26 Parkinson’s studies, each 5 micrograms per cubic meter increase in PM2.5 was associated with about a 10% increase in relative risk, while each 15 micrograms per cubic meter increase in PM10 was linked with about an 18% increase. The findings strengthen evidence for an environmental contribution to Parkinson’s risk, but they do not prove that particle pollution directly causes the disease in any individual. A few extra micrograms of pollution can sound trivial on a city air-quality report. Across years of breathing, however, that difference may matter. A major evidence review links long-term exposure to two forms of airborne particles with a higher risk of Parkinson’s disease. The clearest associations involved PM2.5 and PM10, both small enough to enter the respiratory system. Researchers at the University of Cambridge combined findings from earlier studies that often produced uncertain or conflicting results. The team analyzed 26 studies on Parkinson’s disease. It also …