Study shows CA had worst air quality in US in 2018

Infographic on air quality in Californian cities
Aishwarya Jayadeep/Staff

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California has recently received criticism from the U.S. Environmental Protection Agency, or EPA, for not doing enough to improve its poor air quality, which was the worst in the U.S. last year.

A study published in September by the sleep apnea equipment provider,, concluded that California had the worst air quality in the United States in 2018, based on data gathered by government agencies including the EPA and the Centers for Disease Control and Prevention.

“The main takeaway from the study is simple, many U.S. cities are lacking quality air, and it’s impacting those who live there,” said Matt Gillespie, a project manager, in an email. “It shows the need for better air quality control across the country.”

Campus professor of environmental health sciences John Balmes attributed the poor air quality to two main factors: wildfires and transportation-related emissions.

This is the third consecutive year that Northern California has seen a large wildfire in the fall, according to Balmes. He added that Southern California also faces wildfire risks. Balmes said he believes that wildfire smoke will be an issue the state must deal with “for the foreseeable future.”

Climate change and poor forest management are behind these California wildfires, Balmes said. California’s ecology has evolved to deal with smaller fires, which clean out underbrush from vegetation, according to Balmes. Since humans suppress these fires, however, the undergrowth builds up. When there is a fire, the effects are more drastic.

California is actively working to improve poor air quality, according to Balmes. The state currently has a waiver that allows it to impose stricter restrictions on motor vehicle emissions than those already outlined in the 1970 Clean Air Act. Balmes said the Trump administration is trying to get rid of this waiver, however.

“(The Trump administration is) attacking us for not doing enough to clean our air, and then taking away one of the important tools by which we are cleaning the air,” Balmes said.

The study also found a correlation between poor air quality and low-income levels.

This relationship is seen in the Bay Area when comparing Oakland to Piedmont, a neighboring higher-income town, according to Balmes. Power plants, refineries and highways tend to be concentrated in lower-income areas like West Oakland and Richmond.

“People of color and low income have a greater burden of air pollution exposure from local sources,” Balmes said.

While California faced the poorest air quality in the country in 2018, last year was not an exception, according to Ronald Cohen, campus chemistry and earth and planetary science professor. Emissions get trapped in California’s valleys, which makes air quality worse compared to states with similar emissions per capita, Cohen said.

“However the trends are to cleaner air,” Cohen said in an email. “California has been leading the nation in policies to improve air quality and we continue on a trajectory toward better air quality.”

Contact Emma Rooholfada at [email protected] and follow her on Twitter at @erooholfada_dc.