More than 166 million people in the U.S.—52 percent of all Americans—are exposed to unhealthy levels of either ozone or particulate pollution, putting them at risk for premature death and other serious health effects, including lung cancer, asthma attacks and developmental harm, according to a report published Wednesday by the American Lung Association.

Despite lower ozone levels and long-term averages of particulates, the annual State of the Air report suggests global warming is causing short-term spikes in air pollution. The spikes result from droughts and wildfires that temporarily increase particulate levels from dust and smoke. Wildfires occur more frequently and with greater severity in drier, hotter climates affected by global warming. Seven of the 25 most polluted cities in this year’s report had their highest number of unhealthy short-term particle pollution days ever reported.

“Overall, the trends of ozone and year-round particle pollution continue to go down across the country, but to see these spikes in these communities, that was a surprise to us,“ said Paul Billings, senior vice president for advocacy with the American Lung Association. “This is an indicator of the impact climate change is having, with heat and drought creating conditions that are ripe for high particle pollution days.”

Bakersfield, along with much of central California, had some of the most polluted air while the region continues to experience “exceptional drought.”  The city had the worst long-term and short-term particle pollution and the second-worst ozone pollution after Los Angeles-Long Beach, according to the report. Despite the highest ozone levels in the nation, Los Angeles reported its best air quality ever in the 17 years that the American Lung Association has published its report.

The current report did not assess socioeconomic data but noted that prior studies show the burden of air pollution is not shared equally. “Poorer people and some racial and ethnic groups are among those who often face higher exposure to pollutants and who may experience greater responses to such pollution,” the report stated.

As the planet continues to warm, efforts to reduce air pollution will likely face increasing challenges.

“We need to continue to clean up the sources of emissions that form ozone and particle pollution, but also understand that droughts and wildfires will continue to plague communities as a result of a changing climate,” Billings said.  

Deadly Air

Curbing emissions from power production will play a key role in addressing both human health and climate concerns.

“Burning fossil fuels is a major cause of dangerous levels of air pollution, which kills millions of people each year according to the World Health Organization,” Kelly Mitchell, Greenpeace USA energy campaign director said in a written statement. “We’ve made some progress in the United States by beginning to move away from coal, but we need to go much further here and around the world by transitioning quickly from fossil fuels to 100% renewable energy.”

Implementation of new and existing regulations are needed to reduce harmful emissions said Liz Perera, climate policy director for the Sierra Club. “Enforcement of our Clean Air Act laws in the near term for ozone, sulfur dioxide, and mercury are critical to cleaning up the air. At the same time, the Clean Power Plan is helping to steer us towards clean, renewable energy and energy efficiency.”

The U.S. Environmental Protection Agency passed stringent regulations to reduce sulfur dioxide emissions from power plants in 2010. The rules are now being implemented by state regulators, though not all states are complying. The agency is working to implement similar standards that it created to curb mercury emissions and reduce ozone levels, though industry groups vow to fight the standards in court and in Congress.

The Clean Power Plan, which would reduce carbon dioxide emissions from electricity generation by at least 26 percent by 2025, was put on hold by the Supreme Court earlier this year in response to lawsuits by more than two dozen states and industry groups.

In addition to the rules for power plants, reducing emissions from the oil and gas sector could play an important role. Last week the EPA released new estimates for methane emissions by the oil and gas industry; the updated figures were 34 percent higher than prior estimates. The emissions are significant for both the climate and public health. Methane is a potent greenhouse gas: its release from wells and other infrastructure is often accompanied by the release of volatile organic compounds, which are powerful drivers of ozone production. The revised estimates come as the EPA prepares to release new regulations for methane emissions from the oil and gas industry.

The swift enactment of all pending regulations governing emissions from power plants and the oil and gas industry could have significant implications.

“Addressing climate pollutants and [other] pollutants together will lead to healthier air and a healthier planet but unfortunately, failures to do so or delays will lead to more air pollution and more adverse health consequences,” Billings said.