STOCKTON, Calif. (KTXL) — San Joaquin County has some of the worst air quality in the state, according to the American Lung Association which tracks ozone and particle pollution across the country. 

San Joaquin County isn’t alone, however. Sacramento, Stanislaus, Tuolumne and Calaveras counties were also given failing grades. 

Experts said, despite progress made in the last 20 years, the county’s poor air quality grade didn’t come as a surprise.

“Air quality impacts health. Anyone can be put at risk if there’s a day with unhealthy levels of air pollution,” said Laura Kate Bender, with the ALA. “San Joaquin County did see a few days on which the air quality reached very unhealthy levels.”

Bender said the purpose of the report looking at ozone and particle pollution is to inform people about the air their breathing. 

“If you’re under 18, if you’re over 65, if you have a lung disease like asthma or COPD, if you have heart disease or diabetes, you can be put at greater risk when levels of air pollution are harmful,” Bender said.

Daniel Kim with San Joaquin County Public Health Services said the wildfires across the state in the last few years are just one of several factors that have added to the poor air quality in the San Joaquin Valley region. 

“Geography plays a big role, especially since the Central Valley is really kind of like a big bowl where you know the air generates from north coming down south and it gets trapped by the mountains,” Kim said.

According to Kim, poor air quality may also be a factor in why the county has some of the highest asthma rates in the state. 

A 2016 county health assessment found that one in six children were diagnosed with asthma in the county — the highest in the state at the time. 

While the American Lung Association said what causes asthma is unclear, what is clear is that cleaning up air quality is a matter of public health. 

“We know that this is just another indicator of why we need to clean up the air to address the fact that these — you know, this large community can suffer disproportionate impacts,” Bender said.

The ALA said the failing grade does not reflect efforts being made by the county and other agencies working to improve air quality in the region.