Report highlights dangers of even low concentrations of wildfire smoke

Wildfire smoke paradox

The health impacts of wildfire smoke can rise sharply at low concentrations, according to a new report from the BC Centre for Disease Control.

Titled The Public Health Paradox of Wildfire Smoke, the article was published in the most recent issue of the BC Medical Association Journal. It was submitted by BCCDC researchers, led by Sarah B. Henderson, PhD, scientific director, BCCDC Environmental Health Services.

“Despite human intuition, the relationship between PM2.5 concentrations and acute respiratory outcomes is nonlinear, with steeper slopes at lower concentrations and a plateau at higher concentrations,” notes the researchers.

“The same pattern has been described for long-term PM2.5 exposure and the development of cardiovascular disease. This nonlinear concentration-response relationship is likely due to biological saturation of the cellular processes that cause health harms at high PM2.5 concentrations.”

Wildfire smoke is made up of a mixture of gasses and fine particle matter (PM2.5) but concentrations of PM2.5 are typically used to describe the whole mixture.

Wildfire smoke gets a lot of public and media attention when PM2.5 concentrations are extreme, but according to the study, it causes much more harm at lower concentrations that occur more frequently. The BCCDC says that in B.C., concentrations over 100 µg/m3 are responsible for less than 20 per cent of asthma-related visits attributable to wildfire smoke. However, more than 35 per cent occur at concentrations between 10 and 30 µg/m3.

Decades of research shows PM2.5 exposure is harmful to respiratory, cardiovascular, endocrine, brain and reproductive health.

“The climate in B.C. is changing, and wildfire smoke is starting to dominate our lifetime exposure to air pollution. As with all other types of air pollution, reducing exposure to wildfire smoke will reduce the associated health risks. If we focus our attention on the extreme events and ignore the more moderate impacts, we miss most of our opportunity to protect health. We should collectively start to manage exposures whenever wildfire smoke is affecting air quality,” writes the report’s authors.

The BCCDC suggests the primary focus of prevention should be on clean indoor air, because most people spend the majority of their time indoors. The report says commercial and DIY air cleaners are effective for homes and smaller spaces, but large buildings should have smoke-readiness plans.

“If we combine cleaner indoor air with other simple strategies such as taking it easy outdoors and wearing respiratory protection when appropriate, we can reduce the short- and long-term health impacts of wildfire smoke.”

The full article is available here.

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