Neurological Disorders Significantly Linked with Chemicals in Air Pollution

The results from a long-term study led by researchers at Harvard T.H. Chan School of Public Health of more than 63 million older U.S. adults revealed a significant link between air pollution and an increased risk of hospital admissions for several neurological disorders, including Parkinson’s disease, Alzheimer’s disease, and other dementia-related conditions.

Study Overview

The study is the first nationwide analysis of the link between fine particulate (PM2.5) pollution and neuro-degenerative diseases in the U.S. The researchers examined an unparalleled amount of data compared to any previous study of air pollution and neurological disorders.

Researchers examined 17 years’ worth (spanning from 2000-2016) of hospital admissions data from 63,038,019 Medicare recipients in the U.S. and linked these with estimated PM2.5 concentrations by zip code. Taking into account potential confounding factors like socioeconomic status, they found that, for each 5 microgram per cubic meter of air (μg/m3) increase in annual PM2.5 concentrations, there was a 13% increased risk for first-time hospital admissions both for Parkinson’s disease and for Alzheimer’s disease and related dementias. This risk remained elevated even below supposedly safe levels of PM2.5 exposure, which, according to current U.S. Environmental Protection Agency standards, is an annual average of 12 μg/m3 or less.

Women, white people, and urban populations were particularly susceptible, the study found. The highest risk for first-time Parkinson’s disease hospital admissions was among older adults in the northeastern U.S. For first-time Alzheimer’s disease and related dementias hospital admissions, older adults in the Midwest faced the highest risk.

“Our U.S.-wide study shows that the current standards are not protecting the aging American population enough, highlighting the need for stricter standards and policies that help further reduce PM2.5 concentrations and improve air quality overall.”

-Dr. Antonella Zanobetti, principal research scientist, Harvard Chan School’s Department of Environmental Health and co-author of study


Journal Reference: Shi, L., et al.  Long-term effects of PM2·5 on neurological disorders in the American Medicare population: a longitudinal cohort study, The Lancet Journal of Planetary Health, Open Access, October 19, 2020DOI: