環境：2023年のカナダ山火事の長期的な影響を評価する

Around 354 million people in North America and Europe are likely to have been affected by fine particulate matter pollution (PM2.5) from the 2023 Canadian wildfire season, a paper published in Nature suggests.

Wildfires have contributed to an increase in PM2.5 pollution but the global effect of large wildfires in terms of health and air quality is not well understood. Severe wildfires in Canada between May and September 2023 burned 15 million hectares of forest — the equivalent of around 5% of forested land in the country. Smoke caused by the fires was transported across North America, which led to air quality alerts in the USA, and was also transported to Europe.

Qiang Zhang and colleagues used satellite observations, machine learning and a chemical transport model to explore the global and regional effects of PM2.5 exposure and the associated health impacts of the 2023 Canadian wildfires. The authors found that the wildfires increased annual PM2.5 exposure by 0.17 μg m–3 (micrograms per cubic metre of air) globally, equivalent to 13% of total fire-related PM2.5 exposure in 2023. The Canadian fires also contributed to an increase in PM2.5 levels in the USA that was three times the amount generated by wildfires originating in the USA in 2023. The authors estimate that 354 million people in North America and Europe were exposed to PM2.5 pollution as a result of the Canadian wildfires. They suggest that 5,400 acute deaths in North America and 64,300 chronic deaths across North America and Europe were attributable to PM2.5 exposure from the Canadian wildfires.

The authors suggest that further epidemiological studies are needed and improved monitoring systems that provide accurate air quality information could lessen the effects on human health. They conclude that their findings highlight the long reach of this type of pollution, and the wide-ranging effects wildfires can have.