California's Dirtiest Air, Deadliest Lungs: The 10 Counties With the Worst Respiratory Health
California has some of the worst air quality in the entire country, and the bodies of people living in its most polluted counties are paying the price. The American Lung Association's annual "State of the Air" report and CDC health data consistently show a brutal connection between bad air and skyrocketing rates of asthma, COPD, and respiratory-related death - and in some California counties, those numbers are genuinely alarming. Here are the 10 counties where breathing is, quite literally, a health crisis.
Related: The 10 California Counties With the Worst Air Quality and the Lungs to Prove It · The 10 California Counties With the Worst Air Quality - and Your Lungs Pay the Price
#1 - Kern County
Kern routinely tops the American Lung Association's most-polluted list for both ozone and year-round particle pollution, and the health fallout is real. CDC and CDPH data consistently put Kern among the state's worst counties for COPD prevalence and asthma-related ER visits, with rates running well above the California average. The mix of Central Valley agriculture, oil production, and geography that traps smog makes this one of the most dangerous places in the country to have lungs.
#2 - Fresno County
Fresno has spent decades near the top of national air-quality shame lists, and the ALA's recent reports still flag it for some of the highest ozone-day counts in the state. Asthma hospitalization rates here are roughly double the statewide average, according to CDPH data. Low-income and Latino communities in central Fresno bear a disproportionate share of the burden, a pattern confirmed by CalEnviroScreen, the state's own environmental justice mapping tool.
#3 - San Bernardino County
Inland Empire residents get hit from multiple directions: vehicle exhaust from the massive warehouse and freight corridor along I-10 and I-15, plus ozone that drifts in from the Los Angeles Basin and gets trapped against the San Gabriel Mountains. The ALA has consistently cited San Bernardino for unhealthy ozone levels on a significant chunk of the year's days. CDPH figures show pediatric asthma rates in parts of the county that are among the highest in Southern California.
#4 - Kings County
Tucked between Fresno and Kern in the San Joaquin Valley, Kings County is small but its air-quality and respiratory-health numbers are brutal. CalEnviroScreen scores for several Kings County communities rank in the top percentile statewide for pollution burden. CDPH data points to above-average rates of both asthma ED visits and chronic lower respiratory disease mortality for a county this size.
#5 - Tulare County
Another Central Valley county, another grim air story. Tulare's agricultural activity, including pesticide drift and field burning during harvest seasons, compounds the baseline particulate-pollution problem that plagues the entire San Joaquin Valley. The ALA's particle-pollution data puts Tulare in the danger zone for annual PM2.5 levels, and CDPH tracks elevated asthma-hospitalization numbers here year after year.
#6 - Riverside County
Riverside shares the Inland Empire's air-quality nightmare with its neighbor San Bernardino, and the ALA's reporting treats much of the region as a single pollution zone for good reason. Ozone levels on peak summer days routinely hit the "unhealthy" threshold. The county's fast-growing eastern reaches, places like Coachella Valley, deal with an added problem: windblown dust events that spike PM10 readings and trigger respiratory emergencies.
#7 - Los Angeles County
LA has actually improved dramatically since the 1970s smog era, so its ranking here isn't a slam - it's a numbers game. With roughly 10 million residents, even a modest per-capita rate of respiratory illness translates into an enormous absolute burden on the healthcare system. The ALA still flags LA for ozone exceedances, and CDPH data shows asthma prevalence and related ER visits that, in sheer volume, dwarf every other county on this list. South LA and the 710 freeway corridor remain environmental-justice hotspots.
See also: California's 10 Worst Counties for Air Quality, Ranked · California's 10 Deadliest Counties for Heart Disease, Ranked
#8 - Stanislaus County
Modesto and the surrounding Stanislaus County communities sit squarely in the San Joaquin Valley airshed, and they suffer for it. The ALA's most recent State of the Air report places Stanislaus in the high-risk tier for ozone pollution. CDPH surveillance data shows respiratory-disease hospitalization rates here that track closely with Fresno and Tulare, the valley's most-watched counties.
#9 - San Joaquin County
Stockton's air-quality problems are well-documented, and CalEnviroScreen consistently flags multiple San Joaquin County ZIP codes in the 90th-plus percentile for cumulative pollution burden. The county's position at the northern end of the San Joaquin Valley means it also catches particulate matter that drifts up from agricultural operations to the south. Asthma rates in Stockton's lower-income west side are among the most cited examples of environmental inequity in CDPH's equity reports.
#10 - Shasta County
Shasta earns its spot through a different kind of respiratory threat: wildfire smoke. The county's location in the northern Sacramento Valley puts it in the direct path of smoke from some of California's largest recent fires, and CDC data shows that counties in this region have seen measurable spikes in COPD exacerbations and ER visits for respiratory distress during and after major fire events. The ALA's short-term particle-pollution rankings for Shasta have worsened noticeably over the past several years as fire seasons have intensified.
The throughline here is depressingly predictable: geography, poverty, and pollution cluster together in California just like they do everywhere else. Until air quality in the Central Valley and the Inland Empire gets serious federal and state attention, these counties will keep landing on lists nobody wants to be on.