States with the Worst Air Quality

Whether you live in the city, suburbs, farmland or coast, air quality through your state can vary drastically. We wanted a wider analysis of outdoor air pollution over a three-year period to see how states compared to each other. Since our world drastically changed in 2020, we made sure to look at data pre-COVID-19.

One of the side effects of the pandemic has been pollution improvements in what used to be cities and states with bad air quality. Before and after photos of city skylines in the U.S. and around the world show smog lifting and clearer skies. Studies have shown drops in emissions, and air quality projects across the U.S. have been gathering data to study environmental effects from Covid-19. However, from what studies have revealed so far, PM2.5 and ozone air pollution levels have not dropped consistently despite nationwide shutdowns. Since we didn’t want to look at potentially skewed data affected by the pandemic, we looked at metrics from 2016 to 2018.


States with the Worst Air Quality – Ranked Worst to Best

We analyzed data metrics from America’s Health Rankings on air pollution to compare states. Air pollution data was gathered from the U.S. Environmental Protection Agency and U.S. Census Bureau and rank was determined by analyzing the average exposure of the general public to particulate matter of 2.5 microns or less (measured in micrograms per cubic meter) between the years 2016 to 2018.

State Rank
California 50
Arizona 49
Illinois 48
Pennsylvania 47
Nevada 46
Ohio 45
Indiana 44
Utah 43
Delaware 42
Georgia 41
Texas 40
Oklahoma 39
State Rank
New Jersey 36
Alabama 36
Kentucky 36
Michigan 34
Washington 34
Louisiana 33
Oregon 32
Mississippi 30
Maryland 30
West Virginia 29
Missouri 28
South Carolina 25
State Rank
Florida 25
Tennessee 25
Rhode Island 24
Connecticut 22
North Carolina 22
Arkansas 19
Nebraska 19
Iowa 19
Kansas 18
Virginia 17
Idaho 15
Wisconsin 15
Colorado 14
State Rank
New York 11
Montana 11
Minnesota 11
Alaska 10
Massachusetts 9
New Mexico 8
Maine 7
Hawaii 6
Vermont 4
South Dakota 4
Wyoming 3
North Dakota 2
New Hampshire 1

Interested in how your more immediate area stacks up compared to the rest of the world? Look at real-time air quality data any day of the year to see what you’re inhaling when you’re outside.

Read on to find out more about how outdoor air quality is measured and how you can prevent side effects if you live in one of the states with bad air quality.


What is the Air Quality Index?

The Air Quality Index or AQI is a measure of the six major pollutants that the Clean Air Act regulates. According to the Environmental Protection Agency, the six major outdoor air pollution contributors are:

  • ground-level ozone
  • particle pollution (also known as particulate matter, including PM2.5 and PM10)
  • carbon monoxide
  • sulfur dioxide
  • nitrogen dioxide
  • lead

These pollutants have a national outdoor air quality standard set by the EPA that is meant to protect public health. Air quality is typically the worst on hot and sunny days since these conditions allow ground-level ozone to interact with particle pollution, contributing to the degradation of outdoor air quality. The Air Quality Index, running from 0 to 500, is divided into six categories:

  • Good – Air quality is satisfactory with little to no risk.
  • Moderate – Air quality is acceptable. However, there may be a risk to people who are sensitive to air pollution.
  • Unhealthy for Sensitive Groups – Air quality effects may be felt by members of sensitive groups.
  • Unhealthy – Members of the general public may experience health effects while sensitive persons may experience more serious health effects.
  • Very unhealthy – The risk of health effects is increased for everyone: Will trigger a health alert.
  • Hazardous – Will trigger health warning of emergency conditions, everyone is more likely to be affected.

How to Protect Yourself From Outdoor Air Pollution

Reducing your exposure to outdoor air pollutants is the best way to protect yourself. Check the AQI for your area in real-time and limit outdoor exposure if the results indicate that the air quality falls below “Moderate”. Try not to exercise outdoors and focus on improving indoor air quality (which can often be 5x as polluted as outside!).

States With the Worst Air Quality and Their Asthma Rankings

While examining air pollution data we also came across data on asthma from the CDC, specifically the number of asthma cases and the population percentage of people with asthma in 2018. Since outdoor air pollution can trigger asthmatic episodes and lead to other respiratory issues, we wanted to see if there was a correlation between the states with bad air quality, and the number of diagnosed asthma sufferers. Here are how the states with the worst air quality ranked in this category:

Asthma & Air Quality by State Ranking

State Air Pollution Rank Asthma # of Cases Rank Asthma % of Population Rank
California 50 1 25
Arizona 49 15 50
Illinois 48 7 22
Pennsylvania 47 5 51
Nevada 46 35 29
Ohio 45 8 9
Indiana 43 17 52
Utah 43 33 11
Delaware 40 45 47
Georgia 40 10 18
Texas 40 3 32
Oklahoma 39 28 44
New Jersey 36 11 26
Alabama 36 23 43
Kentucky 36 22 41
Michigan 34 6 42
Washington 34 13 6
Louisiana 33 27 17
Oregon 32 24 40
Mississippi 30 31 5
Maryland 30 19 12
West Virginia 29 36 34
Missouri 28 18 8
South Carolina 25 25 14
Florida 25 4 21
Tennessee 25 16 3
Rhode Island 24 43 37
Connecticut 22 29 45
North Carolina 22 9 7
Arkansas 19 30 2
Nebraska 19 39 19
Iowa 19 34 31
Kansas 18 32 4
Virginia 17 12 24
Idaho 15 41 23
Wisconsin 15 20 16


21 15
New York 11 2 48
Montana 11 44 49
Minnesota 11 26 27
Alaska 10 49 13
Massachusetts 9 14 46
New Mexico 8 37 1
Maine 7 38 35
Hawaii 6 42 10
Vermont 4 47 36
South Dakota 4 48 30
Wyoming 3 51 20
North Dakota 2 50 28
New Hampshire 1 40 38

Is there a correlation between your state’s outdoor air quality and the number or percentage of asthma cases? We’ll leave that up to the experts to decide, and instead, offer tips on how you can make improvements to ease asthma symptoms indoors.

If you happen to live in one of the states with bad outdoor air quality, take steps to improve indoor air by upgrading your air filters to higher MERV ratings, learning about indoor air quality testing, and choosing the right filters for those with allergies and asthma. These preventative steps not only make a world of difference in reducing symptoms for people with respiratory issues, but can improve overall indoor air quality and home wellness, giving you the opportunity to breathe clean air even if outdoor circumstances are not ideal.

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