California wildfire smoke is more toxic than traffic pollution
Environment — di Valentina Neri
Wildfires in California, increasingly frequent and intense, are a demonstration of the climate crisis. A new study explores their health effects.
California wildfire smoke is more toxic than traffic pollution
Wildfires in California, increasingly frequent and intense, are a demonstration of the climate crisis. A new study explores their health effects.
Images of San Francisco and Irvine's fiery skies, crossed by immense columns of smoke and ash, travelled around the world. With the close of California's wildfire season in autumn 2020, the worst on record, scientists set to work assessing the consequences. Their study, published in the journal Nature Communications, reaches a troubling conclusion: the fine particulate matter (PM2.5) produced by wildfires is in fact more toxic than that emitted by traffic or factories.
The health cost of California wildfires
Researchers at the University of California San Diego reviewed hospital admissions data in Southern California over a 14-year period. It is well established that exposure to PM2.5 increases the rate of hospital admissions for respiratory conditions; however, the increase is far more significant when the fine particulate matter originates from wildfire smoke. In that case it ranges between 1.3 per cent and 10 per cent, compared with the 1 per cent observed when fine particles are emitted by road traffic or industrial chimneys.
At the same size — small enough to penetrate the pulmonary alveoli and enter the bloodstream — particles can therefore be more or less harmful depending on their source. Until now, this hypothesis had been supported by laboratory studies, but this is the first time it has been verified in a population. For environmental and health authorities, this is an open question, underlines lead author Rosana Aguilera: the United States Environmental Protection Agency has set certain safety thresholds for fine particulate matter, without, however, taking into account this difference between the various sources.
Wildfires burning around Lake Orville, California, create an orange glow in the sky and on the water.
Human health also depends on the fight against climate change
Full scientific consensus on the reasons behind this phenomenon has not yet been reached. It appears to be partly linked to the materials being burned: in a territory like California, wildfires destroy homes and infrastructure that in turn contain plastics, metals, chemicals, cleaning products and so on. The Guardian also points out that smoke from so-called megafires tends to rise even higher into the atmosphere, where it remains for long periods of time, oxidising and becoming more toxic.
In addressing the severe health consequences of wildfires, one cannot forget that they are also a clear manifestation of the ongoing climate crisis. "Given that conditions in Southern California are becoming hotter and drier, we expect to see an increase in wildfires," notes study co-author Tom Corringham. "This study shows that the damage caused by wildfire smoke may be greater than previously thought, reinforcing the need for early warning systems for wildfires and for action to mitigate climate change."