Close to half of all Americans are breathing unhealthy air, as the quality in the country declines, according to a new report.

The 2020 State of the Air report, released by the American Lung Association, found that for nearly half of the country’s residents, the air they breathe is heavily polluted.

The report analysed air pollution in American cities from 2016 to 2018 and found that levels increased from the 2019 report, which analysed statistics from 2015 to 2017.

More than 137 million people were found to be living in areas where ozone levels rose in the US, which can badly affect those with asthma or other breathing conditions.

The years analysed, 2016 to 2018, were three of the hottest years on record and this contributed to increased ozone levels.

Paul Billings, the national senior vice president of the association, told CNN that “we’re moving in the wrong direction, with nearly 21 million more people breathing dirty air than in last year’s report.”

The American Lung Association CEO, Harold Wimmer, added in a press release that the report is further proof that climate change is affecting people’s health.

“This year’s report shows that climate change continues to degrade air quality and increase the risk of air pollution harming health,” he said.

“To protect the advances in air quality we fought for 50 years ago through the Clean Air Act, we must again act today, implementing effective policies to protect our air quality and lung health against the threat of climate change.”

Cities in California were found to have the highest figures of short-term and year-round pollution, as well as the highest ozone levels, but the report indicates that results were affected by 2018’s wildfires in the state.

Los Angeles had the highest ozone levels, Fresno was found to have the highest short-term particle pollution, while Bakersfield had the highest year-round particle pollution.

Mr Wimmer referenced the coronavirus pandemic to outline the importance of improving air quality for people’s health.