What State Has the Best Air Quality

Climate change, unsustainable industries, garbage disposal systems, heating systems, and so much more that we may or may not be aware of, are contributing to poor air quality in different parts of the world.

Clean air and clean and available water are the elementary preconditions for life to exist. Therefore, the topics such as air quality and air pollution concern us all.

Across the globe, people agree that climate change is one of the most dangerous threats to the world we live in, next to water quality, whose bad effects may be even more immediate.

While the most polluted countries are mainly located in Asia, countries on all continents have critical zones, in which the pollution is reaching dangerous levels.

For example, among the top ten most polluted countries in the world are Bangladesh, India, Pakistan, Mongolia, and Bosnia and Herzegovina. On the other hand, the least polluted countries in the world are Puerto Rico, New Caledonia, and the Virgin Islands in the US, followed by the Scandinavian countries, Estonia, and New Zealand.

But what is the situation inside of the US? Which state in the US has the best air quality? And which one has the worst? Are there any significant differences between the different states in the US even?

In this article, we’ll talk more about pollution, how it is being measured, and which state of the United States of America is the most beneficial one to live in lungs-wise.

How Is the Air Pollution Being Measured and Expressed?

Before we start talking about different states’ pollution levels, we should first talk about how is air pollution being expressed and measured in order to gain a better understanding of what do the standardized measures actually mean.

There are many ways to measure and monitor air pollution. This is usually done by different entities such as governments, research centers, environmental activist groups, etc.

When we talk about air pollutants, we usually differentiate between the PM10 and PM2.5 particles. The PM10 ones are being considered less dangerous, as they are larger, and our bodies will naturally expel them out. On the other hand, the PM2.5 particles are more dangerous, as they are so small, that it’s possible for them to end up inside of our lungs and in our blood.

In cities with busy traffic and lots of constructions sites, the pollution levels usually increase. Those that are particularly dangerous are particles and nitrogen dioxide. These pollutants are being measured with different instruments such as the diffusion tube for nitrogen dioxide and traffic pollution, while the concentration of PM particles is usually being measured using the gravimetric method that involves drawing the air through a preweighed filter and capturing the particles there. There are also different ways to measure the presence of sulfur dioxide, ozone, and many other harmful gases.

Once the pollutants are being measured, there are different ways of expressing their concentration levels.

For example, the presence of both PM2.5 and PM10 particles is being expressed as micrograms per cubic meter (µg/m3), while the measure for gases is parts per million in case of CO and parts per one hundred million in case of other gases.

For proper reporting of the air quality, EPA has developed the AQI index. This index is a scale that goes from 0 to 500, and the greater the pollution, the higher the index number.

If you don’t want to bother yourself with researching and reading about each individual pollutant that may be present in the air in a certain state of your interest, you can simply check the AQI index for the state, and get an overall impression of how satisfactory the living conditions are in that state.

Here is an overview of the AQI numbers and colors that can serve as guidance.

Air Quality Color AQI Index value  Description of the measure
Good Green 0 – 50 Air quality is good, the pollution poses no risk to human health.
Moderate Yellow 51 – 100 Air quality is on an acceptable level, but sensitive individuals may be under a certain level of risk,
Unhealthy for sensitive groups Orange 101 – 150 Sensitive individuals may experience some effects on their health. Those who do not belong to sensitive groups will likely remain unaffected.
Unhealthy Red 151 – 200 People who belong to the general public may experience discomfort and symptoms, while those from the more sensitive groups can expect more serious health issues to occur.
Very unhealthy Purple 201 – 300 The air quality is alarmingly poor, everyone is at risk.
Hazardous Maroon 301 + This level of pollution poses a serious threat to public health. Everyone is likely to be affected.

What State Has the Best Air Quality?

Now that you are familiar with the most common pollutants, methods of measurements, and the most important parameters to be considered, as well as the AQI index of air quality, it’s time to see who is the winner for the US? Which state has the best air quality in the United States?

Perhaps you’ve expected this answer, perhaps not, but the state with the best air quality is Hawaii.

Hawaii ranks as the absolute winner when it comes to both air and water quality, thanks to its rich greenery and nature.

To be even more precise, the Hawaii islands with the cleanest air are Honolulu and Maui, followed by Kahului-Wailuku-Lahaina. These islands persist in having the cleanest air in the entire country, despite the fact that the volcanic smog keeps on increasing.

The reasons behind Hawaii’s clean air probably lie in the fact that there is a lot of wind, but what’s even more important is the low population density. Population density is low even in cities such as Oahu. This appears to be a very important parameter for keeping the air clean.

Furthermore, the Hawaii air likely remains intact by some of the most common pollutants thanks to the fact that there is no heavy industry there. Heavy industries usually dump a lot of pollutants into the atmosphere, thus compromising the health status of the inhabitants of the region.

Only on the days when there is not much wind, you may notice some smog in the air in Honolulu. Also, the volcanic processes may increase the levels of aerosol and sulfate in the air on the days when the wind is blowing from the south.

However, the overall condition of the air in Hawaii islands is considered exceptionally good, although there is always room for improvement. The air quality index in this state rarely crosses 23 AQI, and in Honolulu and Maui, it’s usually between 4 and 9 AQI.

The second best air-quality country in the US is Massachusetts. Despite the fact that they have seen a decrease in air quality, this state is still on top of the game, with AQI index values rarely crossing 45, meaning that on most days of the year, the air quality in the cities of Massachusetts is very good.

Hawaii and Massachusets are followed by North Dakota, Virginia, and Florida, each of them fostering a good air quality throughout the year, with rare oscillations towards the more dangerous part of the spectrum.


Here we conclude the discussion about what state has the best air quality in the US. Although air pollution has risen over the past several years across the planet, some countries and states are succeeding at preserving a good standard of air quality.

Luckily, US states can not be found among the top-ten most polluted in the world, however, you will find them among the top-ten least polluted ones!

When it comes to assessing the pollution levels, the most important things to take into consideration are the PM particles levels (PM2.5 and PM10) that are usually expressed as micrograms per cubic meter, and gases expressed in parts per million (ppm) or parts per hundred million (pph).

For easier understanding of things, EPA has developed an air quality indexing system known as AQI. The scale that is in the range from 0 to 500 expresses the pollution levels of an area from good to hazardous. If you don’t want to bother too much with individual details about pollution levels, you can simply track this AQI index and it is reliable enough information on whether the air in an area is safe to breathe and for which demographic groups (sensitive/non-sensitive).

In the US the state that has the cleanest air is definitely Hawaii, but Massachusetts, Virginia, North Dakota, and Florida are also worth considering, as these make up the top 5 states of the US with the cleanest air.