Wildfire smoke is more toxic than other sources of pollution

The expanding wildfire season in the western United States is causing severe threats to public health, according to a study from the Scripps Institution of Oceanography at UC San Diego. The researchers have found that the fine particles in wildfire smoke are several times more harmful to human respiratory health than particulate matter from other sources of air pollution.

Fine particulate matter (PM2.5) is the main component of wildfire smoke. These particles are so small that they can penetrate the human respiratory tract, enter the bloodstream, and cause damage to major organs.

The analysis was focused on 14 years of hospital admissions data. The experts determined that an increase in PM2.5 by 10 micrograms per cubic meter is up to 10 times more likely to cause a respiratory-related hospital admission when it is attributed to wildfire smoke compared to other sources.

The research suggests that assuming all particles of a certain size are equally toxic may be inaccurate and that the effects of wildfires – even at a distance – represent a pressing human health concern, explained study co-author Rosana Aguilera.

“There is a daily threshold for the amount of PM2.5 in the air that is considered acceptable by the county and the Environmental Protection Agency (EPA),” said Aguilera. “The problem with this standard is that it doesn’t account for different sources of emission of PM2.5.”

It is not yet known why wildfire PM2.5 is more harmful to human lungs than other sources of particulate pollution. Since it is more harmful, the threshold for “safe” levels of PM2.5 should be based on the source of the particles. This is particularly important in California and other areas frequently impacted by wildfires.

Santa Ana winds intensify the air quality issue in Southern California by blowing wildfire smoke toward populated coastal regions. With climate change delaying the start of winter in this region, wildfire season is getting pushed closer to the peak of the Santa Ana winds.

“As conditions in Southern California become hotter and drier, we expect to see increased wildfire activity,” said postdoctoral researcher Dr. Tom Corringham. “This study demonstrates that the harm due to wildfire smoke may be greater than previously thought, bolstering the argument for early wildfire detection systems and efforts to mitigate climate change.”

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer