Air Quality by State 2026: Where Does Your State Rank?
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Alaska has the best average air quality in the United States, with an AQI of 21.1, while Arizona ranks worst at 58.5, according to 2023 EPA data. Out of 50 states and Washington, D.C., 47 have a "good" average AQI (under 50). However, outdoor AQI only tells part of the story. The EPA estimates that indoor air can be two to five times more polluted than outdoor air, making home air filtration a critical factor in overall air quality for most Americans.
TL;DR:
- Alaska (21.1) and Hawaii (27.3) have the best average AQI in the U.S.
- Arizona (58.5), Nevada (58.2), and New Mexico (54.1) rank worst
- 47 out of 51 states/D.C. have "good" average AQI (under 50)
- Indoor air is typically 2 to 5x more polluted than outdoor air (EPA)
- Upgrading your HVAC filter is one of the simplest ways to improve indoor air quality
You check the weather before heading outside. But when was the last time you checked the air quality? For the roughly one in 13 Americans living with asthma, air quality is not just a number on a chart. It shapes daily decisions about exercise, commuting, and even opening a window.
With Air Quality Awareness Week 2026 (May 4 to 8), we mapped every state using the latest EPA data to answer a simple question: how does your state stack up? Whether you live in Alaska or Arizona, the answers might surprise you, especially when it comes to the air inside your home.
Which States Have the Best and Worst Air Quality?
According to EPA air quality monitoring data (2023 averages), Alaska has the cleanest air in the country with an average AQI of 21.1. Arizona has the worst at 58.5. The national picture is mostly positive: 47 out of 51 states and D.C. fall in the EPA's "good" AQI range (under 50).
Top 5 States With the Best Air Quality
| Rank | State | Avg AQI | Rating |
|---|---|---|---|
| 1 | Alaska | 21.1 | Good |
| 2 | Hawaii | 27.3 | Good |
| 3 | Idaho | 29.0 | Good |
| 4 | Montana | 29.9 | Good |
| 5 | Oregon | 30.3 | Good |
What do these states have in common? Low population density, limited industrial activity, and geographic factors (ocean breezes, mountain air) that help disperse pollutants naturally. Alaska benefits from vast wilderness and minimal vehicle emissions, while Hawaii's trade winds and rainfall continuously scrub the air clean.
Top 5 States With the Worst Air Quality
| Rank | State | Avg AQI | Rating |
|---|---|---|---|
| 51 | Arizona | 58.5 | Moderate |
| 50 | Nevada | 58.2 | Moderate |
| 49 | New Mexico | 54.1 | Moderate |
| 48 | Illinois | 50.4 | Moderate |
| 47 | Utah | 49.6 | Good |
Arizona's poor air quality is largely driven by Maricopa County, home to Phoenix and one of the fastest-growing counties in the country. Dust storms, vehicle emissions, and industrial activity all contribute to elevated particulate levels. Nevada and New Mexico face similar challenges due to their arid climates, which trap dust and particulate matter near the surface.
What Is the Air Quality Index (AQI)?
The Air Quality Index is a standardized measurement used by the EPA to communicate daily air quality. It tracks six major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. The index runs from 0 to 500:
- 0 to 50 (Good): Air quality is satisfactory with little or no health risk
- 51 to 100 (Moderate): Acceptable, but sensitive individuals may experience minor effects
- 101 to 150 (Unhealthy for Sensitive Groups): Older adults, children, and those with respiratory conditions should limit outdoor activity
- 151+ (Unhealthy to Hazardous): Everyone should reduce prolonged outdoor exertion
You can check your local AQI anytime at AirNow.gov, the EPA's real-time monitoring tool.
The Hidden Problem: Indoor Air Quality
Here is where it gets personal. Even if your state has a "good" outdoor AQI, the EPA estimates that indoor air can be two to five times more polluted than outdoor air. In some cases, indoor pollutant levels can be 100 times higher.
Why? Your home traps pollutants from cooking, cleaning products, pet dander, dust mites, mold spores, and off-gassing from furniture and building materials. Without proper ventilation and filtration, these pollutants recirculate through your HVAC system every time it runs.
According to the American Lung Association, the average American spends roughly 90% of their time indoors. That means the air filter in your HVAC system is doing far more for your daily air quality than your state's outdoor AQI ranking.
Improving Indoor Air Quality the Sustainable Way
Replacing your HVAC air filter regularly is one of the simplest and most effective steps you can take. The Department of Energy recommends checking your filter monthly and replacing it every 60 to 90 days, depending on factors like pets, allergies, and household size.
But not all filters are created equal, and traditional fiberglass filters come with an environmental cost. Most conventional air filters are made from petroleum-based synthetic materials and end up in landfills after a few months of use. Considering that American households use an estimated 500 million air filters each year, the waste adds up fast.
Aerterra Product Spotlight: A Better Filter for Your Home and the Planet
Aerterra air filters are made from USA-grown corn using plant-based, renewable materials. Unlike traditional synthetic filters, Aerterra uses nanofiber technology to capture particles as small as 0.3 microns while maintaining excellent airflow. Available in MERV 8, MERV 11, and MERV 13 ratings to match your home's needs.
Every order ships free, and the subscription service delivers fresh filters on your schedule so you never forget to swap. Plus, every purchase supports reforestation through a partnership with One Tree Planted.
Understanding MERV Ratings: Which Filter Do You Need?
MERV stands for Minimum Efficiency Reporting Value, a scale developed by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) that rates a filter's ability to capture particles. Higher MERV ratings capture smaller particles, but the best filter for your home depends on your system and your needs:
- MERV 8: Captures dust, pollen, and mold spores. A solid everyday choice for most homes. Shop Aerterra MERV 8
- MERV 11: Also captures pet dander, dust mite debris, and smog. Great for homes with pets or mild allergies. Shop Aerterra MERV 11
- MERV 13: Captures bacteria, tobacco smoke, and fine particulate matter. Recommended for allergy and asthma sufferers. Shop Aerterra MERV 13
Always check your HVAC system's specifications before upgrading. Most residential systems handle MERV 8 to 13 without issues, but some older units may need a lower-rated filter to maintain proper airflow. Consult your system's manual or an HVAC professional if you are unsure.
5 Ways to Improve Your Home's Air Quality Today
- Replace your air filter. If it has been more than 90 days, it is overdue. A clogged filter forces your HVAC system to work harder and recirculates the particles it should be catching.
- Upgrade your MERV rating. Stepping up from a basic fiberglass filter to a MERV 11 or MERV 13 can significantly reduce allergens and fine particles in your home.
- Ventilate when you cook. Use your range hood or open a window. Cooking is one of the largest sources of indoor particulate pollution.
- Control humidity. Keep indoor humidity between 30% and 50% to discourage mold and dust mites. The CDC recommends using dehumidifiers in damp areas.
- Monitor your air. Consider an indoor air quality monitor. Pair it with regular filter changes for a measurable improvement you can track.
Aerterra Product Spotlight: Set It and Forget It
Never miss a filter change again. Aerterra's subscription service delivers plant-based, American-made air filters to your door on a schedule that works for you. Choose your size, pick your MERV rating, and let clean air come to you. Free shipping on every order.
What Is Air Quality Awareness Week?
Air Quality Awareness Week is an annual event coordinated by the EPA to raise public awareness about air quality and its effects on health. In 2026, it runs from May 4 to 8. The week encourages individuals, schools, and organizations to learn about air quality in their communities and take action to protect their health.
It is also a good reminder to check on the basics at home. When was the last time you changed your air filter? If you have to think about it, it has probably been too long.
Learn More About Clean Air and Sustainability
- Our Story -- Learn why Aerterra was founded and what drives our mission
- Why Aerterra? -- See what makes plant-based nanofiber filters different
- How It Works -- Understand nanofiber technology and MERV ratings
- One Tree Planted Partnership -- Every Aerterra purchase supports reforestation
Breathe Easier, Starting Today
Whether you live in Alaska's clean mountain air or Arizona's dusty valleys, your indoor air quality depends on one thing more than anything else: the filter in your HVAC system. The good news is that improving it takes about 60 seconds and a fresh filter.
Aerterra makes it easy to choose a sustainable option. Filters made from renewable, plant-based materials. Nanofiber technology for superior particle capture. Free shipping on every order. And a subscription that takes the guesswork out of filter changes.
Shop air filters by size and MERV rating | Start a subscription | Learn about our reforestation partnership
Frequently Asked Questions
1. How often should I change my air filter?
Most HVAC filters should be replaced every 60 to 90 days. Homes with pets, allergies, or high dust levels may need monthly changes. A dirty filter restricts airflow, reduces efficiency, and allows pollutants to recirculate. Aerterra's subscription service delivers filters on your preferred schedule.
2. What does MERV rating mean?
MERV (Minimum Efficiency Reporting Value) measures how effectively a filter captures airborne particles. Ratings range from 1 to 20. For residential use, MERV 8 to 13 is typical. Higher ratings capture smaller particles, such as pet dander, bacteria, and smoke. Check your HVAC system specs before upgrading, as some systems require specific ratings. Learn more from ASHRAE.
3. What makes Aerterra filters eco-friendly?
Aerterra filters are made from USA-grown corn using plant-based, renewable materials instead of petroleum-based synthetics. The manufacturing process has a lower carbon footprint, and every purchase supports reforestation through a partnership with One Tree Planted. They are also American-made with free shipping on every order.
4. How does a subscription work?
Choose your filter size and MERV rating, select a delivery frequency (typically every 1, 2, or 3 months), and Aerterra ships fresh filters to your door automatically. You can pause, skip, or cancel anytime. Subscriptions include free shipping and help ensure you never forget a filter change.
5. Can the wrong filter damage my HVAC system?
Using a filter with too high a MERV rating for your system can restrict airflow, potentially causing the system to work harder and increasing energy costs. Most residential systems handle MERV 8-13 without issues. Always check your system manual or consult an HVAC professional through ACCA if unsure.
6. Is indoor air really worse than outdoor air?
Yes, in many cases. The EPA reports that indoor air pollutant levels can be two to five times higher than outdoor levels. Cooking, cleaning products, pet dander, and building materials all contribute. Since Americans spend roughly 90% of their time indoors, filtration matters significantly.
7. What is the difference between MERV 8, 11, and 13?
MERV 8 captures large particles, such as dust and pollen. MERV 11 adds capture of pet dander, dust mites, and smog particles. MERV 13 captures bacteria, tobacco smoke, and fine particulate matter (PM2.5). For most homes, MERV 11 offers the best balance of filtration and airflow. Allergy or asthma sufferers may benefit from MERV 13.
8. Where does the air quality data in this article come from?
All AQI data is sourced from the U.S. Environmental Protection Agency (EPA) 2023 monitoring data, as aggregated by USAFacts. AQI values represent population-weighted annual averages by state.
Additional Resources
- EPA Air Quality Data -- Access real-time and historical air quality monitoring data
- AirNow.gov -- Check your local AQI right now
- American Lung Association State of the Air -- Annual air quality report cards
- NADCA (National Air Duct Cleaners Association) -- Find duct cleaning professionals
- NRDC Air Quality Resources -- Research and advocacy for cleaner air
Disclaimer: This article is for informational purposes only. AQI data represents annual averages and does not reflect daily or seasonal variations. For specific HVAC system recommendations or health concerns, please consult with a licensed HVAC professional or healthcare provider. Individual results may vary based on home size, system type, and environmental factors. Air quality data sourced from EPA 2023 monitoring records via USAFacts.
