WForest fires burning in Quebec and surrounding areas create dangerous health conditions throughout North America. On 100 million people were under alert for unhealthy air quality as early as Wednesday, and residents in the Northeast and Midwest — regions that don’t typically face the effects of wildfires — faced hazy, orange-tinged skies and urgent new questions about the harmful effects of air. pollution.

Fine particulate matter, the tiny particles that make up these haze clouds, is a major health problem that is already part of daily life for residents of cities like Beijing, New Delhi and Santiago, Chile. Canadian authorities and U.S. state officials have advised residents in affected areas to avoid unnecessary outdoor activities and close windows and doors.

For those new to air quality issues, here’s what you need to know.

How does air pollution from wildfires impact our health?

Fine particles can be liquid or solid residues from dusty manufacturing sites, car exhaust or soot-covered environments, as well as byproducts of fires, among others. In addition to causing eye irritation, smoke from fires can also carry harmful particles far away.

Particles with a diameter of less than 10 microns are dangerous: they can be inhaled deep into the lungs or even enter the bloodstream due to their small size. From there, they trigger inflammation in the airways and other organs, including the heart, kidneys and liver. Inflammation triggers the body’s defense system, which can damage cells, change gene expression, and lead to scarring and disease.

Even brief exposure to fine particles can be harmful. They were associated with higher hospitalization rates for cardiovascular disease, diabetes and kidney failure.

Particles with a diameter of 2.5 microns or less, or PM2.5, are considered even more dangerous when inhaled at high enough levels. PM2.5 has been linked to an increased risk of heart attack, stroke and lung cancer. This type of air pollution is particularly risky for pregnant people, babies and children, the elderly, and people with lung or heart disease.

Poor air quality can cause or worsen respiratory conditions, such as emphysema, chronic obstructive pulmonary disease – one of the leading causes of death in the United States – and asthma. Children with asthma may experience exacerbations or flare-ups during periods of hazardous air quality.

Recent studies have also shown that exposure to PM2.5 could make the body more vulnerable to infections and neurodegenerative diseases.

Forest fire smoke was found to be among the most toxic to people compared to fine particles from other sources, such as wind-blown dust or soil. This is due in part to the chemical composition of the particles, which is changed by combustion and can trigger a more serious inflammatory response.

Why air pollution is a health equity issue

People who live in low-income communities are disproportionately affected by poor quality water, usually due to their proximity to major polluters, such as factories, ports and highways. But wildfire smoke can also pose particular risks to marginalized communities.

On the one hand, low-income areas and communities of color also tend to have high rates of chronic diseases that make inhaling fine particles even more dangerous. Outdoor workers, including farmworkers, landscapers and construction workers, are also more likely to be frequently exposed to stale air.

As Earth’s climate changes, heat waves like those seen last summer are expected to occur more often – and a heat wave combined with drought, like historic ones in the western United States , means a higher fire risk. People most likely to feel the most severe effects of fire and smoke are those who lack access to well-ventilated housing and workplaces, and affordable health care that allows them to detect quickly The problems.

In the context of future climate change, more than 82 million people will experience a 57% increase in the frequency of smoke waves from wildfires, with the western United States and the Great Plains likely to be most exposed, according to a 2016 study co-authored by Francesca Dominici, co-director of the Harvard Data Science Initiative.

“We are now starting to see” these predictions come to fruition, Dominici said. “I mean, it was very unusual to have this level of wildfire smoke in the eastern United States, and now it’s here.”

Beyond short-term health impacts, wildfire destruction can also have long-term effects on the mental health of communities. Fires can destabilize entire regions as homes and businesses are lost or damaged, and recovery can take place. take years or decades.

“The worrying thing is that, as always, some of the most vulnerable people who have to work outside all day and who already have underlying conditions, or those who cannot protect themselves, are those who run the greatest risk,” said Dominici, who is also a professor of biostatistics, population and data science at the Harvard TH Chan School of Public Health.

What to do about poor air quality

The Environmental Protection Agency recently tightened its air quality standards for particulate matter. But many researchers say the new acceptable pollution levels are still too high and do not sufficiently protect people’s health.

These thresholds, which help local and federal officials develop policies for high-pollution areas, also can do little when environmental crises like Canada’s wildfires arise. EPA rules allow up to 35 micrograms of fine particles per cubic meter of air over a 24-hour period. This week in New York, the level was close to 100 micrograms.

Wearing an N95 mask outside can help, but experts advise people to avoid going outdoors, including exercising outdoors. (People tend to inhale 10 to 20 times more air when they exercise.) Running an air purifier indoors can also help filter particles that enter homes and rooms. offices. The EPA also recommends keeping vacuum cleaners in the closet to avoid blowing particles into the air and turning off wood-burning fireplaces, gas stoves and candles.