If you’re looking for clean air, California may not be the place. Of the top 30 most polluted counties in the U.S., 20 are in the Golden State, according to a 20-year analysis from Healthnews.

That means more than a third of the state is among the worst places to breathe. Two Valley counties, Kern and Tulare, rank in the Top 5 for bad air. Fresno County checks in at No. 7.

“Plowing, harvesting, and other farming operations generate large amounts of dust,” the report stated. “Additionally, practices like agricultural burning and emissions from dairy farms release harmful pollutants into the atmosphere.”

While the figures for the number of unhealthy air days may seem dismal, EPA data show air quality is improving. However, studies also continue to show the health impact of air pollution. A study from the American Cancer Society showed that as fine particulate matter increased, so did risks for lung cancer.

“Fine particulate and sulfur oxide-related pollution were associated with all-cause, lung cancer, and cardiopulmonary mortality,” the study stated.

Are Valley Skies Getting Cleaner?

The San Joaquin Valley Air Pollution Control District in its 2023 report said clean air policies and programs to phase out old technology and curb harmful practices have been successful.

One major help has been a significant decrease in ag burning.

Since 2005, $169 million has been paid out as part of the Air Pollution Control District’s program to curb burning ag waste, diverting 6.6 million tons of ag waste from open burning.

“Over the years, concerted efforts by the District to enhance air quality have yielded significant reductions in both organic carbon and ammonium nitrate,” the Air District’s report stated. “This has been achieved through multifaceted strategies targeting emissions from wood burning, industrial operations, comprehensive incentive programs, and broader state initiatives aimed at curbing vehicle emissions.”

Using Healthnews’ weighted point system, data analyzed by GV Wire shows vast improvements in Fresno and Tulare counties. The five-year period from 2019 to 2023 saw the region’s pollution score dropping by more than half in Fresno and nearly by half in Tulare.

While Fresno County’s pollution score computed to 1,001 from 2003 to 2007, the score dropped to 454 for the most recent five years. Tulare County went from 1,202 to 660.

The number of “good” air days averaged 85 for the most recent time period compared to 45.2 in the past. In Tulare County, “good” air days averaged 70.2 from 2019 to 2023 compared to 42.8 from 2003 to 2007.

Comparing the number of healthy days to unhealthy days, Fresno County used to have a near 1:1 ratio — 1.6 “good” or “moderate” days for every bad one. Now, the county averages more than four “good” or “moderate” days for every bad one.

Oil, Ag Contribute Heavily to Central Valley Air Pollution: Study

Analysts at Healthnews examined 20 years of air quality data from the EPA from 2003 to 2023. Looking at the number of unhealthy days, they weighted the score for the four different categories, one point for “unhealthy for sensitive groups,” two points for “unhealthy,” three points for “very unhealthy,” and four points for “hazardous.”

San Bernadino, Riverside, and Kern counties took the top three spots with pollutions scores above 4,000.

San Bernadino and Riverside suffer in large part because of air currents that move the L.A. basin’s air pollution to the Inland Empire, according to the study. Los Angeles County ranked fifth.

Tulare County came right behind Kern with a score of 3,709, giving it the No. 4 spot.

In the 20 years analyzed, Tulare County reported 2,797 bad air days. That means 38% of the time, air quality was less than ideal.

The study attributes poor air quality in Tulare County to agricultural practices and the county’s topography. Plowing and harvesting generates large amounts of dust. Dairy farms also generate large amounts of methane. The Sierra Nevada and coastal ranges also cause pollutants to linger rather than dispersing them.

Farther south, oil production in Kern County contributed to that region’s poor air.

With 9,000 wells on 10,000 acres, the Kern River Oil Field is one of the densest in the nation.

“The oil extraction process releases harmful gasses like volatile organic compounds and nitrogen oxides due to leaks and fuel combustion in drilling equipment,” the report stated. “These pollutants react with sunlight to form ground-level ozone, a major component of smog.”