Not just bad for your lungs; air pollution damages your brain, McMaster University researchers say

Avoiding exposure to air pollution doesn't just protect your lungs. It also protects your brain, a McMaster University professor says.

Russell de Souza says his team found higher long-term exposure to two common air pollutants was associated with "small differences in brain health that we could measure."

De Souza, a professor in the Hamilton university's Department of Health Research Methods, Evidence, and Impact, is coauthor of a study published May 13 in the journal Stroke.

That study looked at how exposure to common air pollutants affected the performance of about 7,000 Canadians on tests of brain health, de Souza told CBC's London Morning radio show.

The participants, recruited between 2014 and 2018, had an average age of 57 and came from British Columbia, Alberta, Ontario, Quebec and Nova Scotia. Researchers examined their exposure to air pollution during the five-year period prior to the study.

One of the pollutants in question was fine particulate matter, which is commonly found in wildfire smoke, industrial emissions and car exhaust. The other was nitrogen dioxide, a gas also found in vehicle exhaust.

The researchers tested brain health using the Montréal Cognitive Assessment, in which subjects try to remember words, and the Digit Symbol Substitution Test, where they match numbers and symbols.

"Together, these tests show us what the brain can do and how efficiently it can do it," de Souza said.

The study found exposure to both air pollutants resulted in lower scores on both brain tests.

"It's nothing severe that people are going to notice, and feel horrible and extremely forgetful all of a sudden," but it shows we can measure these declines early and stop them before they get worse, de Souza said.

Overall, the professor said, air pollution in Canada has been "a success story," leading to this region having "some of the cleanest air in the world."

However, recent years have seen "climate-driven wildfires" offset some of those gains, he said.

Generally, de Souza said, air pollution is highest near airports, highways and freight yards. He said people should check daily air quality advisories to best understand their local risk.

A Health Canada website says you can reduce exposure to fine particulate matter indoors through measures including cleaning and ventilation. It said you can limit your nitrogen dioxide exposure in part by properly venting gas appliances and avoiding idling cars in enclosed spaces.

Health Canada notes exposure to nitrogen dioxide increases the risk of developing breathing problems, and exposure to fine particulate matter can affect breathing for at-risk people.

A McMaster news release notes de Souza's team's research was conducted as part of a study called Canadian Alliance for Healthy Hearts and Minds with funding from the Canadian Partnership Against Cancer, the Heart and Stroke Foundation of Canada, and the Canadian Institutes of Health Research.

It says long-term follow-up studies "are needed to better understand how ongoing exposure to air pollution may influence cognitive decline over time, and whether improving air quality can help protect brain health."