A Breath of Fresh(er) Air: Average Concentration of Air Pollutants in the US Fell Between 2012 and 2022

There may be a silver lining amid the haze: The average concentration of air pollutants in the U.S. fell over the past 10 years. However, some metros have better air quality than others. As climate change contributes to more frequent and severe wildfires, some places may be particularly prone to unhealthy air.

The newest ValuePenguin study will highlight which metros have the most air pollution and explain how air quality plays a role in health insurance.

Key findings

The concentration of air pollutants in the U.S. fell over 10 years

Generally speaking, air pollution in the U.S. has fallen. This applies to two major types of air pollution: fine particulate matter (PM2.5) — tiny inhalable air particles — and ozone — the main ingredient in smog. Between 2012 and 2022, PM2.5 levels decreased by 15.2%, while ozone levels decreased by 12.5%.

Average air pollution concentration in the U.S. by year

According to ValuePenguin health insurance expert Divya Sangameshwar, this is a direct result of the U.S. government’s commitment to clean air, which began in 1970 with the Clean Air Act. In fact, since the Clean Air Act was enacted, outdoor air pollutants have decreased by 78%, according to the EPA.

California metros dominated places with the most air pollution

While air pollutants have fallen overall, that doesn’t mean the country is pollutant-free. In fact, those who live in California are particularly less likely to enjoy clean air. Of the 10 metros with the most air pollution in 2022, eight were in California.

According to Sangameshwar, that’s likely due to the high number of wildfires in the state.

Visalia, Calif., led here with an average annual PM2.5 concentration of 20.7 µg/m3. While Visalia didn’t experience any wildfires in 2022, there were 10 wildfires in the surrounding areas, burning at least 3,104 acres combined. Smoke from wildfires can travel hundreds or thousands of miles, according to the EPA — making it likely that each wildfire impacted the air quality in Visalia. Additionally, the EPA states Visalia’s surrounding mountain ranges in the San Joaquin Valley trap air pollutants and pollution sources from heavy traffic on nearby roadways.

10 metros with the most air pollution in 2022

Following that, Bakersfield, Calif. (16.0 µg/m3), and Eugene, Ore. (15.7 µg/m3), had the next highest levels of air pollution. In 2022, there were six wildfires surrounding the Bakersfield area, burning 4,264 acres.

On the other hand, the metros with the lowest average PM2.5 concentration were Kahului, Hawaii (2.5 µg/m3), and Honolulu (3.7 µg/m3). That may be due to the trade winds in the area. In an interview with Hawaii Public Radio, ALA Hawaii executive director Pedro Haro attributed the high rankings among several Hawaii metros to the Pacific trade winds pushing out pollution to the middle of the ocean.

Rounding out the bottom three was Duluth, Minn., at 3.8 µg/m3.

Full rankings

Metros with the most/least air pollution in 2022

38.3% of measured days in Riverside, Calif., in 2022 had unhealthy air

Riverside, Calif., ranked highest here: 38.3% of the days measured in Riverside in 2022 had unhealthy air, meaning 93 days had an AQI level of 101 or higher. While Riverside had two major fires in 2022 (burning a combined 170 acres), this metro was particularly exposed to pollutants carried from Los Angeles over air currents.

Phoenix (27.4%) followed. The Arizona metro has more sunlight and less cloud cover than others, making it more prone to ozone pollution. Additionally, high temperatures raise ozone layers, and the temperatures in Phoenix regularly exceeded 100 degrees Fahrenheit during summer 2022.

Finally, Visalia rounded out the top three at 21.7%.

5 metros with the highest percentage of days with unhealthy air in 2022

Overall, there were 25 metros where average AQI levels were 51 or higher, meaning the air quality was moderate or worse. Of these, Riverside again made the top of the list, with an average AQI level of 84. Phoenix (77) and Los Angeles (70) followed.

There’s some good news, though, as 248 metros had no days of unhealthy air quality in 2022.

In 2021, Phoenix had the highest percentage of days with unhealthy air

Looking only at metros with 365 days of recorded data, we also determined which metros had the highest percentage of days with unhealthy air the previous year in 2021. Phoenix ranked first here, with 237 days of unhealthy air. At 64.9%, that’s almost two-thirds of the year. Phoenix also had the highest average AQI levels at 123.

Following Phoenix, Riverside had 166 days of unhealthy air quality (or 45.5% of the year), while Visalia experienced 134 days (or 36.7%). Riverside also had the second-highest average AQI, at 97. Bakersfield, Calif., had the next-highest average AQI at 84.

Meanwhile, 61 metros with full data had no unhealthy air quality days in 2021.

Full rankings

Metros with the highest percentage of days with unhealthy air in 2022

Metros with the highest percentage of days with unhealthy air in 2021

As wildfires spread through Canada, New York City experienced several days of unhealthy air in a short period

While air quality has improved overall, climate change may make further progress difficult. New York offers a recent example of that: As smoke from wildfires in Canada billowed over New York City, air quality dropped significantly.

Between June 13 and July 12, 2023 — the latest 30 days at the time of our research — New York City recorded an average AQI of 74, reaching a high of 158 on June 30. In total, there were eight days of unhealthy air — meaning more than 1 in 4 days in New York had unhealthy air.

New York City air quality, June 13 to July 12

As climate change worsens, wildfires will likely continue to contribute to poor air quality — particularly because wildfires contribute to higher ozone levels and more particulate matter. In 2022, there were 66,255 wildfires in the U.S., burning 7,534,403 acres. As of Aug. 17, 2023, there have been 35,382 wildfires across the U.S., which have burned 1,679,776 acres.

Air quality and health insurance: What to know

From reducing lung function to causing cancer, poor air quality can harm our health. But what does that mean for our health insurance? According to Sangameshwar, it likely means increased health care costs.

"Thanks to poor air quality, Americans may need to spend a lot more money on medication use, emergency department visits, hospitalizations and testing," she says. "For the nearly 56% of Americans enrolled in high-deductible health plans, these potential expenses may not even be fully covered by their insurance plans or savings in their health savings accounts (HSAs)."

While insurers can’t raise your rates or deny you coverage for a preexisting condition, Sangameshwar says unhealthy air quality could also have a longer-term impact on insurance premiums in your area. Even if you remain unaffected by poor air, it could lead to others in your area getting sick — which could cause insurers to raise rates, citing an increase in their costs.