Wildfire Smoke is Becoming a Public Health Threat

California’s wildfire smoke crosses the United States on the jet stream in 2017. Image: NASA

As wildfires rage across the Western United States each summer and fall, the immediate headlines of these disasters focus on the destruction and displacement they cause. However, as we’ve seen this summer, states like California and Colorado have been engulfed by wildfire smoke that’s subsequently spread across the rest of the country. Yet we know relatively little about how prolonged exposure to wildfire smoke affects human health.

As the BBC recently reported, smoke from burning forests and peat can linger in the atmosphere for weeks, traveling thousands of miles and harming the health of populations living far away.

Why This Matters: Just like with the mental health effects that afflict people recovering from natural disasters, we must also look more closely into the longterm health consequences posed by exposure to wildfire smoke. In fact, the NIH estimates that wildfire smoke causes 339,000 premature deaths every year and BBC’s reporting noted that it could also be shortening life expectancies for populations that experience fire seasons regularly.

For babies and young children, they’re especially susceptible to the adverse health effects of exposure to the fine particulate matter in smoke. We don’t know for certain all the ways in which wildfire smoke harms children and babies but we can get an idea from how they’re affected by air pollution in general.

Dangers of Wildfire Smoke: Wildfire smoke isn’t a uniform substance. Firstly it depends on what’s burning (forests, grass, shrubland etc.), how hot the fire is, as well as a person’s distance from the source of the smoke. As Luke Montrose, assistant professor of Community and Environmental Health at Boise State, explained, “The distance affects the ability of smoke to “age,” meaning to be acted upon by the sun and other chemicals in the air as it travels. Aging can make it more toxic. Importantly, large particles like what most people think of as ash do not typically travel that far from the fire, but small particles, or aerosols, can travel across continents.”

Montrose further elaborated that smoke from wildfires contains thousands of individual compounds, including:

  • Carbon monoxide,
  • Volatile organic compounds (VOCs),
  • Carbon dioxide,
  • Hydrocarbons
  • Nitrogen oxides.
  • The most prevalent pollutant by mass is particulate matter less than 2.5 micrometers in diameter, roughly 50 times smaller than a grain of sand. Its prevalence is one reason health authorities issue air quality warnings using PM2.5 as the metric.

According to the Journal of Thoracic Disease, PM25 (particles less than 2.5 micrometers in diameter) can penetrate deeply into the lung, irritate and corrode the alveolar wall, and consequently impair lung function.

A Lingering Issue: The BBC also noted that wildfire smoke can hang in the atmosphere for days, weeks or even months depending on the duration of the wildfires causing it. This is in part because the superheated smoke and ash rising into the air can trigger pyrocumulonimbus events, or fire-induced thunderstorms.

  • These thunderstorms form at least 10 miles (16 km) above the ground in the stratosphere where they’re moved by the winds and weather in the jetstream, allowing smoke particles to stay in the stratosphere for weeks.
  • This also allows wildfire smoke to travel huge distances. Large wildfires can send smoke billowing across whole continents and even oceans.

As climate change continues to make wildfires more frequent and destructive, we should treat the smoke resulting from them as an urgent public health threat and prepare affected populations accordingly.

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