The Bay Area has some of the worst air quality in the nation but numbers have gradually improved over the last few years, the American Lung Association said in a report released last week.
The Bay Area ranked sixth in the list of most-polluted metropolitan areas for short-term particle pollution and 10th in most-polluted cities for year-round particle pollution, according to the lung association's State of the Air 2018 report.
In Santa Clara County, the ozone level received a "F" grade and short-term particle pollution levels, measured within a 24-hour span, was given a "C" grade according to the report. The average year-round particle pollution received a passing grade.
Bakersfield was ranked worst for short-term particle pollution while Fairbanks, Alaska, was worst for the long-term pollution, the report said.
Despite the poor rankings, the lung association said strong state and local clean air programs in California are driving progress.
The Bay Area -- the report added San Joaquin County to the region in the results -- experienced a 70 percent drop in unhealthy ozone days since 2000 and an 80 percent drop in unhealthy particle pollution days since 2004.
The lung association's senior director of air quality and climate change Bonnie Holmes-Gen said unhealthy levels of pollution can cause premature death, asthma, chronic obstructive pulmonary disease and lung cancer if conditions do not improve.
"We must continue the life-saving work of cutting air pollution and slowing climate change," Holmes-Gen said in a statement.