Agriculture and wildfire emissions are the most detrimental to cognitive health

Over recent years, a great deal of evidence has been uncovered to make a link between air pollution and susceptibility to dementia but new research suggests that air pollution from farming and wildfire sources might be particularly problematic.

Boya Zhang and Sara Adar, environmental epidemiology researchers in University of Michigan’s School of Public Health uncovered the possible link in their research ‘Comparison of Particulate Air Pollution From Different Emission Sources and Incident Dementia in the U.S.’ which was published yesterday.

The researchers used data from the Health and Retirement Study (HRS), a nationally representative cohort of older adults in the US. Since 1992, participants have been interviewed biennially about their cognition, overall health, and health behaviors until death or loss to follow-up. The HRS replenishes its sample every six years to account for the aging of the original cohort.

All participants older than 50, with at least two interviews between January 1, 1998, and December 31, 2016, were eligible for the study if they were free of dementia at their first interview during this period. The total number of participants was close to 30,000.

The study used a sophisticated prediction model that included information about the chemical transformations and dispersion of pollution from different sources to estimate the levels of source-specific particulate matter air pollution at participants’ residential addresses.

Zhang, a research fellow who focuses on the effects of air pollution on cardiopulmonary disease and cognitive aging, said: ‘This approach is beneficial because it not only accounts for pollution directly emitted by a source but also pollution generated through reactions with other chemicals in the air.’

It was observed that higher levels of particulate matter air pollution, especially from agriculture and wildfires, were associated with greater risks of dementia. The findings could not be explained by other factors such as individual, neighborhood, socioeconomic status, occupation, or hometown or region of the country.

Zhang said: ‘This work suggests that particulate matter air pollution from agriculture and wildfires might be more neurotoxic compared with other sources. However, more research is needed to confirm these effects, especially for these two sources which have received less attention in prior research.’

Wildfire smoke has been a particular problem for the US this year with the blazes in Canada affecting air quality across much of North America.

Wildfires are thought to contribute up to 25% of fine PM2.5 exposure over a year across the country and as much as 50% in some western areas and they are, of course, becoming increasingly common.