Living in one of the US states with the cleanest air is vital for your health. According to the American Lung Association, 4 in 10 Americans live in areas with toxic air. When exposed to contaminated air for prolonged periods, it can cause severe heart and lung problems.
The Environmental Protection Agency (EPA) monitors air quality in the US and safeguards public health with the NAAQS. With authorization by the Clean Air Act, the EPA can perform these duties. Each US state is assigned an Air Quality Index (AQI) value, allowing them to be ranked according to air cleanliness. When it comes to US states with the cleanest air, the overall highest air quality is in Hawaii.
This article will inform you about which state has the cleanest air. We’ll also walk you through how air quality is measured. Let’s get started.
Table of Contents
Measuring Air Quality
While looking into the US states with the cleanest air, you’ll encounter the Air Quality Index (AQI). As you can probably tell, this index measures the air quality. It identifies four primary air contaminants:
- Ground-level ozone
- Particle pollution/particulate matter
- Carbon monoxide
- Sulfur dioxide
- Nitrogen dioxide
The Clean Air Act, a federal law regulating air emissions, standardizes the Air Quality Index. In addition, it gives the Environmental Protection Agency (EPA) the authority to set National Ambient Air Quality Standards (NAAQS). The NAAQS regulates dangerous air pollutants and protects public health and welfare.
The AQI determines which state has the cleanest air by categorizing and assigning each state a value. This ranges from zero to 500. Zero represents US states with the cleanest air, while 500 is the most hazardous level.
A value of 100 or below is favorable because it shows that the air doesn’t pose any health risks. Values above 100 represent unhealthy air, which poses health risks to specific groups of people. The more the AQI value increases, the less safe the air is to breathe.
There are various technologies available today that monitor air quality. Regulatory authorities like the EPA established and designed the Federal Reference Method (FRM) to fulfill air quality monitoring criteria.
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Categories of the Air Quality Index (AQI)
The Air Quality Index is split into six categories, each of which poses different levels of health concerns. These include:
- 0-50 AQI – These values are represented by the color green. It shows that air quality is good and poses little to no health risk.
- 51-100 AQI – These values are symbolized by the color yellow. The air quality is moderate. If you’re sensitive to air conditions, you may experience some respiratory symptoms.
- 101-150 AQI – These values are represented by the color orange. Since they’re out of the safe range, the air quality isn’t healthy for sensitive groups. This includes anyone with lung disorders or ailments.
- 151-200 AQI – These values are represented by the color red. The air quality is unhealthy, so you may feel the effects of the poor conditions. If you’re sensitive to air conditions, the effects may be more intense.
- 210-300 AQI – These values are denoted by the color purple. The air quality conditions are incredibly unhealthy.
- 301-500 AQI – These values are represented by the color maroon, and the air quality conditions are dangerous.
Other Air Quality Metrics
According to the American Lung Association, a clean state has low ozone levels (smog) and particle pollution (PM2.5 or soot). Ozone air pollution, or ground-level ozone, is one of the most prevalent. It occurs when toxins from cars, chemical plants, power plants, and other sources react with sunlight.
The Environmental Protection Agency defines particle pollution as a blend of solid and liquid particles found in the air. And particle pollution comes from fires, cooking, vacuuming, unpaved roads, construction sites, etc. Particulate Matter (PM) is one of several common air pollutants. They’re easily inhaled through the nose and mouth, causing irritation in the nasal cavity and other health issues.
A clean US state is also defined by a low percentage of cigarette usage by adults. So, now that you have an idea of air quality measurement let’s explore the US states with the highest air quality.
Top 10 US States With the Cleanest Air
We ranked each state based on the metrics above and the State of the Air Report by the American Lung Association. In addition, we considered air pollution data from America’s Health Rankings to set each state’s standing. Bear in mind that worsening climate conditions will cause the level of air cleanliness in your state to fluctuate.
1. Hawaii
The natural beauty of Hawaii has been long preserved, allowing the state to boast pristine beaches and an inviting tropical atmosphere. This preservation has also given it an upper hand regarding air quality compared to other states. Hawaii has, on average, the cleanest air in the USA overall. It has an AQI value of 21.2, which is in the healthy range set by the EPA.
The American Lung Association ranks two cities in Hawaii in the top 25 cleanest US cities for year-round particle pollution. Honolulu ranks third, while the Kahului-Wailuku-Lahaina metro area ranks fourth. Honolulu is also ranked as the cleanest for ozone air pollution and short-term particle pollution.
Hawaii has an air pollution rating of 4.3. It stands immediately after Wyoming, considered the healthiest state in terms of air pollution by America’s Health Rankings. Hawaii is also one of ten states with the lowest cigarette usage among adults.
Environmental shifts resulting from volcanic activity and climate change are the most significant risks to the air quality in this state. To mitigate this, the state has a clean energy initiative in place. They aim to achieve 100% clean energy by 2045.
2. Maine
Maine is the second of the US states with the cleanest air. The air quality in this state has significantly improved in the last decade, affording it an Air Quality Index of 36.5. However, not all cities in Maine enjoy clean air. Also, despite Maine’s high overall ranking, the state has high lung cancer rates and cigarette usage amongst adults.
Bangor is by far the cleanest in terms of ozone air pollution and short-term particle pollution. The American Lung Association ranks the city fifth in the top 25 cleanest US cities for year-round particle pollution. Portland is ranked as the cleanest for short-term particle pollution. Still, its year-round particle pollution continues to get worse.
Maine is mitigating the emissions from power plants through the Transportation and Climate Initiative (TCI) Program. This program aims to improve air quality, invest in cleaner public transportation, and reduce carbon emissions that worsen climate change.
3. North Dakota
With an Air Quality Index of 37, North Dakota is the third of the US states with the cleanest air. The state also ranks in the top ten states with the lowest air pollution in the US. It has an air pollution value of 4.8.
North Dakota meets the EPA’s federal ambient air quality standards, but some counties may negatively affect the overall air quality. This includes Mercer County, which has coal-based power plants. And McKenzie and Williams counties, which have gas-powered plants.
Bismarck is considered one of the cleanest cities for ozone air pollution and year-round particle pollution. Fargo is also included on these lists for ozone air pollution. Overall, North Dakota’s urban areas are progressing well by maintaining clean levels of air.
The greatest threat to the air quality in North Dakota, besides the power plants in various counties, is wildfires. Ash and soot have been noted to drift from wildfires in Montana, Wyoming, and southern Alberta to the state.
4. Vermont
According to the American Lung Association, Vermont has consistently ranked as one of the US states with the highest air quality. This is all thanks to the state’s commitment to clean air. Vermont started clean-ups of coal-fired power plants and aged diesel engines in the past decade.
These activities have afforded the state an Air Quality Index value of 38.5 and an air pollution value of 4.9. The Burlington-South Burlington-Barre metro area is amongst the cleanest in the country regarding air quality. It’s noted for its low ozone air pollution and short-term particle pollution.
Wildfires in neighboring states are a significant threat to the air quality in Vermont. In addition, when smog and soot drift from other areas, it can decrease the air quality in the state.
5. New Hampshire
New Hampshire lies at the midpoint of the top ten US states with the cleanest air. The state has an Air Quality Index of 38.9 and an air pollution value of 4.3. In fact, it’s the second state after Wyoming with the cleanest air, according to America’s Health Rankings. However, it shares this position with the state of Hawaii.
Wildfires on the West Coast negatively affect the air quality in New Hampshire, as is the case in many other states. In addition, these wildfires increase particle pollution. This might explain why no New Hampshire cities have ranked on the American Lung Association’s cleanest cities report.
6. New York
New York is one of the most populated states keeping air pollution to a minimum. The state achieved a ranking as the sixth of the US states with the cleanest air. New York’s Air Quality Index is 40.4, and it has an air pollution value of 6.3.
These values may not be as low as you’d expect, but it’s a significant improvement for the state. Thanks to clean air laws and regulations, the air quality in New York is improving. Despite the primary airports and abundance of cabs, air pollution has dwindled. If not significantly, slightly.
Elmira-Corning ranked as the cleanest in all three categories of the American Lung Association’s report. Ozone air pollution, year-round particle pollution, and short-term particle pollution were lower than in other cities not on the list.
The Rochester-Batavia-Seneca Falls metro area was also considered the cleanest in terms of short-term particle pollution. Syracuse-Auburn is another New York metro area that ranked best in short-term and year-round particle pollution.
7. Massachusetts
The state with the seven-highest air quality in the US is Massachusetts. It has been a leader in air quality in the country. Massachusetts has an Air Quality Index of 41.4 and an air pollution value of seven.
Springfield is the cleanest city in the state in terms of short-term particle pollution. The Boston-Worcester-Providence metro area received the same ranking by the American Lung Association. Pittsfield had low year-round ozone particle pollution.
Massachusetts is also part of the Transportation and Climate Initiative (TCI) Program. The program aims to reduce transportation pollution and carbon emissions that worsen climate change and improve air quality. This program can significantly improve the air in heavily trafficked metro areas in the state, including Boston and Springfield.
8. Virginia
Virginia’s Air Quality Index is 45. It has an air pollution value of 6.5, setting it as the 13th least polluted state in terms of air. Several cities ranked as the cleanest in the state in the American Lung Association’s State of the Air report.
Charlottesville received a ranking as the 21st city with low year-round particle pollution. The city also came away with the best standings for ozone air pollution and short-term particle pollution. Lynchburg ranked 18th of the top 25 US cities with the cleanest year-round particle pollution.
Ozone air pollution and short-term particle pollution were low in the Harrisonburg-Staunton metro area, Roanoke, and the Virginia Beach-Norfolk metro area. Blacksburg-Christiansburg had low ozone air pollution, while Lynchburg and Richmond had low short-term particle pollution levels.
9. Delaware
The Air Quality Index of Delaware is 46.4. According to America’s Health Rankings, the state has an air pollution value of 8.3. This places it as the 39th polluted state in the US.
Delaware is considered one of the most polluted states, mainly because of New Castle County. However, the county has made great strides to reduce pollution, hence why it’s the ninth cleanest state in the US. Also, Delaware is one of ten states with the lowest lung cancer rates.
Over the past 30 years, Delaware has implemented strategies to reduce emissions. This includes enforcing stricter rules on refineries, power plants, and manufacturing sites. New Castle County is still making its way out of pollution, giving the state lower ratings in terms of air quality.
10. Maryland
Maryland is the tenth of the US states with the cleanest air. It has an Air Quality Index of 47. And an air pollution value of 6.7, as set by America’s Health Rankings.
Coal-burning power plants contribute to air pollution in the state of Maryland. However, through strict regulations, emissions have decreased. This allowed the state to make it onto our list.
The 5-county Salisbury-Cambridge MD-DE metro area ranked on the ALA’s list of the cleanest cities in terms of short-term particle pollution. Maryland is also one of ten states with the lowest cigarette usage among adults and the least lung cancer rates.
The Bottom Line: US Sates with the Cleanest Air
The quality of the air we breathe in is vital to our well-being. When exposed to contaminated air for extended periods, it can lead to serious respiratory illnesses. What’s more, it can worsen conditions for those at risk of respiratory diseases.
Hawaii is one of ten states with the overall cleanest air. It tops the charts for several regulators and authorities in the air quality space. This includes the American Lung Association, America’s Health Rankings, and the Environmental Protection Agency.
If you live in a state with a high AQI, invest in a quality facemask when walking outdoors. Also, reduce the time you spend outdoors to lower exposure to pollutants. This is especially wise if you live in an area prone to wildfires. In addition, since pollutants from the outside can seep into your house, fitting your HVAC system with a quality air filter is vital.
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FAQs about US states with the cleanest air
How Is the Air Quality Index Calculated?
To calculate a city or state’s Air Quality Index, regulators use the air quality measurements in the area. These measurements are taken over a standard time interval, 24 hours or 8 hours, for ozone and carbon monoxide. They contain average concentrations for particular pollutants, including ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and fine particulate matter.
The index is then calculated using these average concentrations and set breakpoints of pollutants, with the highest value applied. In areas with multiple pollutants, the principal value is reported.
What Is a Good Air Quality Index?
An Air Quality Index (AQI) value between zero and fifty shows clean air. The air you breathe in poses little to no risk for your health, so you can enjoy outdoor activities. An AQI value above 50 is dangerous and can cause serious health problems. This is especially true for older adults, children, and those with lung ailments and illnesses.
What Happens If Air Quality Gets to 500?
An Air Quality Index (AQI) value of 500 represents hazardous air quality. This means the air contains toxic levels of pollutants. Exposure to air of this quality could cause respiratory and cardiovascular issues, such as asthma and an irregular heartbeat. When the AQI value in an area reaches 500, you’re advised to stay indoors.
Remaining indoors will protect your health, but you’re not entirely safe. You’ll need to maintain or improve the air quality in your house by ensuring your HVAC system has a proper air filter.
Where Can I Monitor the Air Quality for My State?
You can keep track of the air quality in your state through the Environmental Protection Agency’s website: AirNow. The daily AQI reading in your state and city during any given hour will be available. These readings are color-coded, making it easier to read and determine what the air quality is like outdoors. Air Quality Index reports are disseminated via apps and social media as well.
What Will Breathing in Polluted Air Do to My Health?
Breathing in excessive amounts of polluted air can cause health issues that vary from temporary to terminal. Some short-term effects include sore throat, chest infections, and dry coughs. If you remain exposed to polluted air, these problems will worsen. However, if you don’t, they’ll improve.
Some severe side effects are the risk of cancer development, heart attacks, and strokes. That’s why it’s essential to keep yourself safe from excessive exposure to pollutants.
How Do I Protect Myself from Poor Air Quality?
Check the air quality forecast in your city before stepping out of your house. Also, avoid working or exercising outside when the air quality is low. Wearing a quality facemask can also go a long way in protecting you from poor air quality.
Bear in mind that polluted air can enter your house as well. That’s why it’s vital to purchase good air filters for your HVAC system to protect you from toxins.
Which Cities Have the Cleanest Air in the US?
According to the American Lung Association’s State of the Air report, the city with the cleanest air is Cheyenne, Wyoming. This is based on year-round particle pollution measured for the city. After Cheyenne are Wilmington, Urban Honolulu, then the Kahului-Wailuku-Lahaina metro area. The fifth cleanest city in terms of air is Bangor, Maine. It’s followed by Casper, Bellingham, Bismarck, and Elmira-Corning, New York.
How Do I Measure the Air Quality in My House?
You can measure the air quality in your house by purchasing an indoor air quality monitor. These devices typically detect everything from VOCs to formaldehyde. Testing for mold in the air is another way to measure the air quality in your house.
Carbon monoxide alarms are an excellent investment to alert you when the CO levels in your house are high. Lastly, you can conduct a radon test.
How Do I Improve the Air Quality in My House?
You can improve the air quality in your house by investing in higher quality air filters for your HVAC system. The best air filters block fine particles and debris from entering your house. These have a MERV rating of at least 13 or higher. Upgrading the air filters in your house is one of the best ways to improve the air quality in your home.
Which Season in the US Has the Worst Air Quality?
There’s no specific season with the worst air quality in the US. However, some pollutants are worse than others in the summer, while others are worse in the winter. This is because the same atmospheric conditions that cause different weather affect air quality.
These conditions include temperature, humidity, and air pressure. They can affect the ozone and particulate concentrations present in a specific area.
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