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Study strengthens link between air pollution and dementia

Over the next 30 years, an aging population will triple the number of dementia cases globally, from 50 million to more than 150 million.

Up to 40% of those cases are linked to potentially avoidable factors like air pollutants.

Now, a paper in the journal BMJ by the Harvard T.H. Chan School of Public Health offers the strongest evidence yet linking dementia risk to fine particulates in the air such as PM-2.5s — particles measuring 2.5 microns or less.

The meta-analysis of 51 studies includes cases found through active case ascertainment methods like community outreach, contact tracing and targeted testing.

These active approaches found a stronger link than passive studies, possibly due to misclassifications in the electronic health records they often use. The fact that many dementia risk factors cluster together — such as socioeconomic group and ethnicity — makes teasing out causes from diagnostic records that much more difficult.

Several studies included in the analysis showed the link stayed strong even when annual exposure fell below the current EPA annual standard of 12 micrograms per cubic meter of air (µg/m3).

Globally, PM2.5 levels range from less than 10 µg/m3 in cities like Toronto, Canada to more than 100 µg/m3 in cities such as Delhi, India.

Analysis of more limited data also suggests links between dementia and nitrogen oxide and nitrogen dioxide, gases released during combustion that cause air pollution, smog and acid rain.

Although particulates pose a smaller risk than factors like smoking, far more people are exposed to air pollution, which kills more than 6.5 million people globally each year.

People can limit exposure by staying indoors and filtering air, but many people live and work in areas where exposure is inescapable. Consequently, experts tend to view regulatory solutions as more effective.

The EPA is now considering a proposal to strengthen PM2.5 regulations.

Nicholas Gerbis joined KJZZ’s Arizona Science Desk in 2016. A longtime science, health and technology journalist and editor, his extensive background in related nonprofit and science communications inform his reporting on Earth and space sciences, neuroscience and behavioral health, and bioscience/biotechnology.Apart from travel and three years in Delaware spent earning his master’s degree in physical geography (climatology), Gerbis has spent most of his life in Arizona. He also holds a master’s degree in journalism and mass communication from Arizona State University’s Cronkite School and a bachelor’s degree in geography (climatology/meteorology), also from ASU.Gerbis briefly “retired in reverse” and moved from Arizona to Wisconsin, where he taught science history and science-fiction film courses at University of Wisconsin-Eau Claire. He is glad to be back in the Valley and enjoys contributing to KJZZ’s Untold Arizona series.During the COVID-19 pandemic, Gerbis focused almost solely on coronavirus-related stories and analysis. In addition to reporting on the course of the disease and related research, he delved into deeper questions, such as the impact of shutdowns on science and medicine, the roots of vaccine reluctance and the policies that exacerbated the virus’s impact, particularly on vulnerable populations.