North America wildfire smoke as bad as ‘secondhand smoke in bars’

As air quality in North America suffers again due to Canadian wildfire smoke, discussion is taking place about how dangerous this smoke actually is. 

Particulate matter has become part of everyday conversation in the US this Summer but those conversations have tended to focus on the amount of the pollution, rather than focussing on what it actually is.

Appearing on CBS News Philadelphia Jose Laurent from the Rutgers School of Public Health warned that the wildfire smoke potentially more dangerous than car emissions.

Health reporter Stephanie Stahl asked him: ‘If trees are burning in these wildfires how is that more toxic than emissions from cars?’ To which Jose replied: ‘That initial smoke reacts with the air, reacts with the sun, leading to a change in the chemical composition.’

During the worst air pollution episodes of the Summer, the Nanoscience and Advanced Materials Center at the Environmental and Occupational Health Sciences Institute and the Rutgers School of Public Health completed a measurement campaign to characterise the physicochemical and toxicological properties of wildfire air pollution.

A peak was reached on June 7, when the average concentration of PM2.5 between 3 pm and 7pm was 330 mg/m3, which the team compared to secondhand smoke in bars before the smoking bans, and way above the 35 mg/m3 24-hour limit of National Ambient Air Quality Standards. 

The samples collected during this campaign are still under analysis to better understand their physical and chemical composition to help the researchers better understanding of the impacts of wildfires on human health and climate change.

Jose Laurent’s comment about the smoke reacting with the sun is supported by research conducted by the University of Georgia last year.

The team from Georgia, led by Associate Professor Rawad Saleh, knew that as smoke rises into the atmosphere, its chemical make-up is altered by exposure to the sun but set out to discover how much.

Anthony Wexler, a professor and the director of the Air Quality Research Center at the University of California, Davis said of the research (in which he was not involved): ‘That smoke is hanging out there for days and days and days, and it’s getting chemically cooked. And there are interesting questions there about how that’s changing the toxicity of this stuff.’

Salah’s team burned and tested three woods typical of those that might be involved in a Southeastern USA wildfire: oak foliage, pine needles, and hickory twigs. They burned the wood inside an environmental chamber calibrated to mimic the light intensity, temperature, and humidity of a summer day at noon. To age the smoke, the researchers turned on UV lamps, allowing the smoke to bake in the ‘Sun’ for two hours.

Lung cells were exposed to PMs from fresh and ‘aged’ smoke and it was found that the fresh smoke disrupted the way cells store and use energy but the aged smoke led to higher levels of cell death. The research is limited because of its simplicity – it strictly looks at wood smoke when wildfires burn everything in their path – but it establishes that while both fresh and aged smoke are toxic, they are toxic in different ways.



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