By now, everyone has seen the photos of New York City’s skyline smothered in a cloud of smoke, formed by the record-breaking wildfires in Canada’s Quebec and Nova Scotia provinces. New York’s Air Quality Index reached "hazardous" levels, prompting dire public health alerts, school shutdowns, and the cancellation of outdoor activities.

Closer to home, Washington, DC, experienced its highest particle matter reading in more than 20 years, as smoke from the Canadian wildfires drifted down the East Coast. It prompted a near unprecedented “Code Purple” Alert warning of “very unhealthy” air across the region, and NBC Washington's Chief Meteorologist Doug Kammerer reported, “Air quality is the worst we have seen in the DC area since records were kept.”

We asked American University Professor of Environmental Science Valentina Aquila to explain why this is happening now, it’s impact on health, and how concerned we should be.

What is the effect of wildfires on air quality, and how concerned should we be?   

The smoke from the burning of biomass contains particles with a diameter of one or two micrometers, about 20 times or more smaller than the thickness of a human hair. When inhaled, these small particles can penetrate deep in the lungs and cause health conditions such as bronchitis or asthma attacks. Exposure to smoke particles can aggravate chronic conditions and even cause premature death.  

While the number of wildfires per year in North America has not increased since the 1980s, the extent of area burned has. This is connected to climate change: the longer, warmer, and drier summers are creating optimal conditions for the spreading of wildfires and prolonging the fire seasons in many regions. Once a spark ignites a fire, the dry vegetation provides fuel to grow it and the warm temperatures and dry winds make the fire hotter and more difficult to contain. The energy generated by the fire propels the smoke high in the atmosphere, where it travels long distances.

This is the reason why, right now while I am writing this piece, the sky in DC is hazy and the EPA recommends not to perform physical activities outdoors: widespread fires from Canada are transported by the winds all the way down the East Coast, causing smoke concentrations that the EPA classifies as “unhealthy.” This has happened before. During the past couple of weeks, DC was impacted by smoke from forest fires in New Jersey and Nova Scotia, and as far as Alberta. In July 2021, a trail of poor air quality formed from large wildfires in Oregon and Washington State across north America all the way to the East Coast, following the wind flow.

We do not expect these climate-related trends to stop or reverse any time soon, as long as climate change will continue unabated. Land management practices such as prescribe burning and the planting of fire-resistant tree species can help reducing the availability of fuel and slowing down and containing wildfires. On an individual level, we can implement precautions and limit our exposure to smoke. Airnow.gov provides a real-time map of the air quality index, color-coded in terms of risk. While short exposures to smoke does not generally represent a risk for healthy individuals, it is always a good idea to pay attention to local air quality reports.

About Professor Valentina Aquila

Professor Aquila joined AU’s Department of Environmental Science in 2017. Her research focuses on the role of solid and liquid particles (aerosols) on the Earth’s atmosphere and climate. Currently, she is principal investigator for a NASA project to understand the role that volcanic eruptions and forest fires has played in the climate during the satellite era. Prior to AU, Aquila worked as a researcher at NASA and Johns Hopkins University. She earned a master’s in physics from the University of Genoa, Italy, and a PhD in meteorology from the Ludwig Maximilian University of Munich, Germany.