Dementias Linked to Air Pollution
Parkinson’s, Alzheimer’s, and other dementias are linked to air pollution, new research finds, adding neurological degeneration to the growing list of effects attributable to fine particles. A study of 63 million adults older than 65 in the United States showed that from 2000 to 2016, first-time hospital admissions for Parkinson’s, Alzheimer’s disease, and related dementias rose 13 percent with every 5-microgram (per cubic meter of air) increase in annual concentrations of PM2.5, fine particles smaller than 2.5 millionths of a meter in diameter. Such particles are produced principally during the burning of fossil fuels, especially coal and oil. The risk remained elevated even at concentrations below 12 micrograms per cubic meter, the level the U.S. Environmental Protection Agency currently deems safe.
Photograph courtesy of Harvard T.H. Chan School of Public Health
“Our study builds on the small but emerging evidence base indicating that long-term PM2.5 exposures are linked to an increased risk of neurological health deterioration, even at PM2.5 concentrations well below the current national standards,” said Xiao Wu, a doctoral student in biostatistics at the Harvard T.H. Chan School and co-lead author of the study, which was published online October 19, 2020, in The Lancet Planetary Health.
Antonella Zanobetti, principal research scientist in the Harvard Chan School’s department of environmental health and co-senior author of the study, said the new research results show that current U.S. regulations are insufficient to protect the aging American population, “highlighting the need for stricter standards and policies that help further reduce PM2.5 concentrations and improve air quality overall.”
Photograph by Shanying Liu
Women, white people, and urban populations, particularly in the Northeast, were particularly at risk, the research showed. The researchers speculate that the increased effects on urban populations (of equivalent levels of fine particles) might be due to the “abundance of metal-bearing nanoparticles in the urban atmosphere, which have very small diameters and can access the brain directly.” They attribute the increased risk to women and white people to greater longevity (the probability of death from other causes before developing dementia is higher in men and nonwhites). To learn more about the dangers of fine particle pollution and the use of big data to detect its health impacts, read “Air Pollution’s Systemic Effects” from the March-April 2020 issue of Harvard Magazine. “Clearing the Air,” a feature article from the magazine’s archives, explains some of the mechanisms linking air pollution to poor health.