West Coast Cities Experienced World’s Worst Air Quality in September

Minuscule particles in smoke may cause long-term health impacts, which will overlap with flu season and the Covid-19 pandemic

Satellite image shows thick smoke over Oregon and Washington in September
Nine counties in California, Oregon and Washington had Air Quality Index values over 500, which is usually the maximum measurement on the scale. NASA Worldview

An analysis of the United States Environmental Protection Agency’s air quality data shows that about 50 million people in California, Oregon and Washington—equivalent to one-in-seven Americans—experienced “unhealthy” or worse air quality this September, Audrey Carlsen, Sean McMinn and Jess Eng report for NPR.

The air pollution stems from the wildfires that continue to burn across the West Coast. The fires have burned not just forests, but also buildings and other infrastructure, which release noxious gases from the chemicals used during construction, Amy McKeever, Ryan Morris and Brian Jacobs report for National Geographic.

Washington’s King County, which includes Seattle, saw the most days with “hazardous” air quality out of those analyzed, per NPR. And Portland, Orgeon, faced pollution that tops records in Delhi, India, one of the world’s most polluted cities, National Geographic reports. Now, experts are trying to research and predict how poor air quality will affect health outcomes in both flu season and the ongoing Covid-19 pandemic.

By the end of September, California’s wildfires rapidly approached four million acres of land burned, Olga Rodriguez reports for the Associated Press. The smoke from September fires traveled as far as the Netherlands, but those living with the densest smoke spent days under orange skies.

Smoke’s smallest particles, known as PM2.5, are one of the biggest health hazards. At less than 2.5 microns in diameter, the particles can get past barriers like nose hairs, which filter out larger particles, and embed deep in a person’s lungs. The tiny particles can cause headaches, coughing, shortness of breath and a racing heartbeat, Healther Kelly and Samantha Schmidt report for the Washington Post. The smoke is especially dangerous for people with chronic respiratory problems like asthma.

PM2.5 particles are one of five pollutants calculated into the Air Quality Index, which communicates how hazardous the air quality is at a given time. The scale stretches from zero to 500. At 101, the air is unhealthy for at-risk people, and it’s unhealthy for all groups when it reaches 151.

Marion County in Oregon hit an AQI measurement of 710 on September 11, per NPR, and eight other counties across the three West Coast states also broke the limits of the AQI scale. Thirty-six counties had not recorded very unhealthy air quality until this year.

“At these levels, even healthy people will start feeling symptoms,” Gopal Allada, a pulmonary and critical care expert at the Oregon Health & Science University School of Medicine, told the Washington Post in September.

The effects of the annual wildfire season have become more common in recent years because of climate change and land management, per the Washington Post. But this year’s fire season started unusually early because of lightning storms in mid-August. (The August Complex is still burning and about 51 percent contained as of October 2, according to Cal Fire.)

Persistent poor air quality is linked to heart and respiratory problems, but there is only limited research available because persistent pollution from wildfire smoke is a new issue in the United States.

"This is not well studied because this has become more of a phenomenon in the last decade, where we've had these major fires across the world," says pulmonologist Karthik Mahadeva to NPR. "We don't know what the long-term impacts are going to be for our patients."

New research suggests that the smoke may have indirectly caused hundreds of deaths of people over 65 years old, per National Geographic. And PM2.5 exposure may cause long-term lung damage in older people as well. But University of Montana immunologist Christopher Migliaccio is most worried about the overlapping seasonal flu, Covid-19 pandemic and ongoing smoke pollution.

A recent study showed that air pollution can make people more prone to respiratory disease like the flu, which may spark a domino effect. Migliaccio tells National Geographic, “If you have an increase in influenza cases, that makes people more susceptible to other respiratory infections like pneumonia or coronavirus.”

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