The Environmental Protection Agency (EPA) tracks air quality — including the presence of pollutants and potential health hazards — and reports its findings in the Air Quality Index (AQI). Using AQI records from 2011 to 2020 and historical data from 2000, 1990 and 1980, ValuePenguin investigated the effects of air quality on residents' health.
From 2011 to 2020, the EPA tracked air quality in 1,157 counties out of 3,143. Those counties with an average of 302 or more days a year where the air quality was "good" — posing little or no risk to the health of nearby people — had better air quality than the other 75% of counties where measurements took place. At the state level, 288 days was the threshold for the top quarter.
In the states with an average of 288 or more good-quality days during this period — 2011 to 2020 — health insurance costs were 9% cheaper than in the states with fewer good-quality days. Moreover, per-person Medicare spending — different from the amount individuals spent on private health insurance through state exchanges — was 3% lower in counties with 302 or more good-quality days than the rest of the counties.
- The average cost of health insurance is 9% cheaper for those living in states with the absolute best air quality. In states where the air quality is good for 288 days or more a year — the top 25% of good days — health insurance costs 9% less than states with fewer good air quality days.
- The median income of people who live in counties with poorer air quality tends to be slightly less ($899 a year) than those who live where the air is cleaner. Residents living in counties with fewer days with good air quality make just 1% less than their counterparts.
- Hawaii County, Hawaii, had the highest number of days where the air quality was classified as unhealthy. An annual average of 228 days from 2011 to 2020 were unhealthy, compared to the national average during this period of just five.
- Good air days are getting more common. In 2020, there was an average of 279 good-quality days across the 326 days for which data was collected — a rate of 85%. In 1980, there was an average of 166 good-quality days across 295 days, or 56%.
Residents of states where air quality is most frequently rated "good" pay 9% less, on average, for insurance than the rest of the country
ValuePenguin organized counties and states into groups according to the average number of days each has per year where air quality was rated as "good." Counties that had at least 302 good-quality days a year from 2011 to 2020 have better air quality than 75% of the rest of the counties the EPA kept data on during this period. For states, this benchmark was 288 days a year.
|Top 25% of states||$552|
|Bottom 75% of states||$604|
Table shows the average cost of health insurance per group, from 2017 to 2020, for states, according to air quality.
In the states where the number of good air quality days is greater than or equal to 288 a year, health insurance rates tend to be more affordable than in places where good air quality days are less common. In the states in the top 25% for the number of good days, the average cost of health insurance is $552 a year. In the other three-quarters of states, rates are $604 a year — a difference of 9%.
States arranged from high to low by number of good-quality days, determined by AQI.
ValuePenguin also found a similar disparity in the amount spent on Medicare at the local level. In counties with 302 or more good air quality days per year — at which 25% of counties have more days with good air quality than the other 75% — Medicare spending was 3% more affordable than places where good days were less common.
Medicare is available for people 65 or older, as well as other groups based on eligibility. It covers hospital costs, doctor's visits and medications. Consumers may supplement it with additional Medicare Advantage plans.
|Top 25% of counties||$8,886|
|Bottom 75% of counties||$9,147|
Table shows expenses by group for Medicare spending per capita, according to air quality.
On average, per capita Medicare spending comes to $8,886 a year in counties with 302 or more good air quality days per year and $9,147 with fewer. At the same time as they experience more expensive health insurance coverage premiums, people living in counties with fewer than 302 days with good air quality make slightly less than those living in counties with better air quality. In fact, the average median household income from 2011 to 2020 for those in the lower 75% of counties is $899 less a year than their counterparts.
9 counties averaged more than 100 unhealthy air quality days annually from 2011 to 2020
In this study, unhealthy days are ones where the air quality may be dangerous for sensitive groups who have lung or heart disease or who are older. For our purposes, unhealthy days also include what the EPA deems "unhealthy," "very unhealthy" and "hazardous," when toxins and pollutants in the air are so persistent that those who aren't necessarily a part of these sensitive groups may be affected.
From 2011 to 2020, there were nine counties with an average of more than 100 days a year when air quality was unhealthy — and six of these posted unhealthy days for more than a third of a year. The most likely to have poor air quality during this period was Hawaii County, Hawaii, home of Hawaii Volcanoes National Park — which may contribute to the county's relatively high number of unhealthy days. The county was the only one to average more than 200 days a year of unhealthy air. The next-highest county — Riverside County, Calif. — averaged 144 of these days.
From 2011 to 2020, the EPA collected air quality data every day of the year in Los Angeles County, Calif. During this period, the county typically had only 35 days a year where the air quality was good — the lowest among this group.
The average number of unhealthy days for all counties included in this study was just five per year, from 2011 to 2020, while there were typically 245 good quality days per year.
Difference from average
Difference from average
|San Bernardino, Calif.||142||2,629%||44||-82%|
|New Madrid, Mo.||142||2,624%||185||-24%|
|Los Angeles, Calif.||114||2,102%||35||-86%|
Counties and states ordered by average number of unhealthy days.
While Hawaii County had the highest average number of unhealthy days during this period (228), it also saw the largest improvement to the number of good-quality days per year. In 2011, there were just 13 good-quality days in the county, while that number increased to 352 in 2020.
On average across the counties with data from both years, there were 40% more good-quality days in 2020 than in 2011. However, there were many counties where the average number of days with good air quality fell during this period — sometimes substantially.
The EPA observed air quality on an average of 327 days in 2020 and 313 days in 2011. Among the counties where the EPA recorded observations for at least this many days, air quality decreased by the most in Maricopa County, Ariz. The EPA maintained a full year's worth of data on air quality in 2011 and 2020 in Maricopa County, and the data shows that there were 70% fewer days with good air quality there in 2020 than in 2011.
Change to the number of good-quality days, 2011 to 2020
The following table displays the counties where the EPA recorded air quality data in 2011 and 2020 for a typical number of days — on average, this was 313 days in 2011 and 327 in 2020. The final column shows the change in the number of good-quality days in 2020 compared to nearly a decade earlier.
|2||Los Angeles, Calif.||253%|
|9||St. Bernard, La.||140%|
|11||St. Louis City, Mo.||137%|
|12||District of Columbia, D.C.||133%|
Table shows counties with at least the average number of observed days per year in 2020 and 2011.
The average number of days per year with good air quality has gone up since 1980, while unhealthy and moderate days have both declined during the same period
The air is getting cleaner. Data from the EPA indicates that the average number of good-quality days has gone up 28% since 2011. Also, the number of good-quality days has increased by 62% since 2000.
At the same time, the number of unhealthy days and moderate days are both declining. Since 2011, there have been 44% fewer days where the average air quality was classified as unhealthy. Since 2000, the number of unhealthy days has dropped by 74%. Similarly, the number of moderate days — days where air quality is generally unharmful except to very sensitive groups — has fallen, too, by 45% since 2011.
In other terms, the share of days when the air quality is good is getting larger. Across 295 days in 1980 where air quality was recorded, 56% were rated good quality. In 2020, that number was 85% across an average of 326 measured days.
At the same time, 18% of days in 1980 were unhealthy and 25% were of moderate quality. In 2020, the air quality on 13% of days was moderate, while just 1% were unhealthy.
ValuePenguin analyzed air quality changes by state and county in the U.S. using the Environmental Protection Agency's (EPA) Air Data, collected from monitors across the country. The EPA gathered data from 1,157 counties during this period, though the number of days monitors recorded air quality varies by location.
Researchers utilized the EPA's Air Quality Index (AQI) measurements from 2011 to 2020 and in 2000, 1990 and 1980. This data represents local air quality as good, moderate or unhealthy and tallies the number of days per year the air quality was classified as such. The five pollutants covered by the AQI are:
- Ozone (O3)
- Particulate matter (PM10 and PM2.5)
- Carbon monoxide (CO)
- Nitrogen dioxide (NO2)
- Sulfur dioxide (SO2)
Analysts combined air quality readings with health insurance rates by state and Medicare expenditures per capita. Researchers analyzed both sets of data, published by the Centers for Medicare and Medicaid Services (CMS). Health insurance rates span 2017 to 2021, while expenditure data comes from 2011 to 2019 — all the most recently available data.
Researchers also gathered income data from the U.S. Census Bureau. Income data is based on five-year estimates that span the entirety of the 2011-2019 period.