Why Air Quality Should Factor Into Your Move

People researching a relocation typically check cost of living, crime rates, school quality, and job markets. Air quality rarely makes the list, until it should. The difference between the cleanest and most polluted US counties is not marginal: some counties report over 300 "Good" AQI days per year, while others in the same state report fewer than 200.

For people with asthma, COPD, cardiovascular conditions, or young children, this difference is medically significant. Even for healthy adults, chronic exposure to elevated PM2.5 and ozone levels is associated with increased cardiovascular and respiratory risk over time. Five years in a county with 30 unhealthy days per year is meaningfully different from five years in one with 3.

PlainAir's county-level data makes this comparison straightforward. Each county page shows the AQI breakdown, primary pollutants, trend data, and how the county compares to state and national averages.

Median AQI: The Single Most Useful Number

What it tells you: The median AQI represents the typical day in a county. A median of 35 means half the days in the year had AQI below 35 (solidly in the "Good" range). A median of 55 means the typical day is at the upper edge of "Good" or into "Moderate", not dangerous, but consistently less clean.

What it does not tell you: The median hides the extremes. Two counties can have the same median AQI of 40, but one might have zero unhealthy days while the other has 15, if those 15 days are severe enough, the average still washes them out. Always check the unhealthy day count alongside the median.

How to use it: On PlainAir's rankings page, sort by median AQI to find the cleanest counties. Then check each county's unhealthy day count to make sure the median is not masking seasonal problems.

Unhealthy Days: The Number That Matters for Sensitive Groups

What it tells you: The count of days with AQI above 100 (Unhealthy for Sensitive Groups or worse) is the most actionable metric for health-conscious relocation decisions. If you or a family member has a respiratory condition, this number directly predicts how many days per year outdoor activity should be limited.

What it does not tell you: Not all unhealthy days are equal. A day at AQI 101 is very different from a day at AQI 300. The count also does not tell you when the unhealthy days occur, 10 unhealthy days spread across the year is less disruptive than 10 consecutive days of wildfire smoke.

How to use it: Compare candidate counties' unhealthy day counts on PlainAir. For respiratory-sensitive households, prioritize counties with fewer than 5 unhealthy days per year. Check the 5-year trend to see if the number is stable, improving, or worsening.

What This Means for You: A Relocation Framework

Step 1, Identify candidate counties. Start with your shortlist of potential relocation areas. Look up each county on PlainAir and note the median AQI, unhealthy day count, and primary pollutant.

Step 2, Check the 5-year trend. Is air quality improving or declining? Western counties near wildfire-prone forests may show worsening trends even if current-year data looks acceptable.

Step 3, Understand the primary pollutant. If ozone is the main driver of unhealthy days, that is a summer heat problem, it may not bother you in winter. If PM2.5 is dominant, check whether it is from wildfire smoke (seasonal) or industrial/traffic sources (year-round).

Step 4, Compare to where you live now. Context matters. If your current county has 20 unhealthy days and a candidate has 8, that is a meaningful improvement. If your current county has 2, even 8 may feel like a step backward.

Frequently Asked Questions

Which US cities have the best air quality?

Counties in coastal Maine, northern Minnesota, Vermont, and the Pacific Northwest coast report the most Good AQI days. Check PlainAir's county rankings for 2020-2025 data.

Is air quality better in rural or urban areas?

Generally yes, but agricultural burning and wildfire smoke can affect rural counties significantly. Some rural counties also lack monitoring stations. Coastal and high-elevation urban areas sometimes outperform nearby agricultural regions.

How many unhealthy air days per year is acceptable?

The national average for monitored counties is roughly 5-15 unhealthy days. Fewer than 5 is excellent. More than 20 indicates significant seasonal challenges. For respiratory conditions, even a few days can be consequential.

Does air quality change over time or is it stable?

It varies. Many urban areas have improved due to regulations. Some western counties have worsened due to wildfire activity. PlainAir shows 5-year trends for every county so you can see the direction.