Updated April 2026 · EPA Air Quality System
Personal Exposure Estimator
Select your city and enter how many years you've lived there to estimate your cumulative unhealthy air days, dominant pollutant exposure, and whether air quality is improving or worsening.
According to EPA air quality data analyzed by AirHistory.org, cumulative exposure to unhealthy air days is an important health metric. The EPA defines 'unhealthy' as AQI above 100, when air quality may begin to affect sensitive groups including people with asthma, heart disease, and older adults.
What This Estimator Actually Computes
Cumulative exposure here is a simple product: the city's 5-year median AQI multiplied by the number of years you've lived there. The output is a dose-proxy in AQI-years, useful for comparing two cities or two time windows but not a clinical measurement. Long-run exposure to fine particulate matter (PM2.5) is the better-documented health risk in the United States; ground-level ozone matters most for people who exercise outdoors regularly. Both feed the AQI on which the estimate is based, so the proxy implicitly captures the dominant pollutants in the city.
The dose-response evidence linking long-run AQI exposure to measurable health outcomes — cardiovascular disease, respiratory illness, reduced lung function, low birth weight, and pollution-attributable mortality — is documented in WHO air-quality guidelines, EPA's Integrated Science Assessments, and decades of peer-reviewed research. The American Lung Association's annual State of the Air report is a useful complementary read.
How to Read the Output
The estimator returns several signals. The dominant pollutant tells you which contaminant most often drove the daily AQI category in your city's EPA records — that is the contaminant whose source mix (vehicle exhaust, industrial emissions, wildfire smoke, dust) you've been most exposed to. The trend slope tells you whether the absolute level has been falling, holding steady, or rising during your tenure. And the unhealthy-days count, scaled to your years of residency, gives a concrete sense of how many calendar days of exposure to "Unhealthy for Sensitive Groups" or worse air you accumulated.
For a long-tenure resident in a worst-tier city, those numbers add up quickly: a city averaging 40 unhealthy days per year over 25 years of residency means roughly 1,000 days of elevated-AQI exposure across an adult lifetime. That kind of cumulative dose is meaningful, particularly for residents with asthma, COPD, cardiovascular disease, or pregnancy.
Reducing Future Exposure
Personal mitigation tools are concrete and effective. A well-sized HEPA air cleaner cuts indoor PM2.5 by 80%+ during smoke or pollution episodes; for someone who spends most non-work hours at home, that single tool can be the largest single reduction in personal exposure. AirNow alerts at the zip-code level let you shift outdoor exercise to lower-AQI windows. N95/KN95 masks meaningfully filter PM2.5 during outdoor activity on bad-air days; surgical masks do not.
For long-term decisions, the cleanest-air cities ranking shows where U.S. air runs reliably below the national average — useful context for retirement, relocation, or work-from-anywhere decisions where air quality is a meaningful input. The fastest-improving cities ranking shows where the trend is steepest — useful when staying in your current metro is the default choice. And the methodology page documents exactly how each AQI number is computed.
Frequently Asked Questions
How is "cumulative exposure" calculated?
The estimator multiplies the city's 5-year median AQI by the number of years you indicate. That gives a rough cumulative dose proxy in AQI-years — useful for comparing two cities or two time windows, not a clinical measurement. Real-world exposure depends heavily on whether you spend time outdoors during peak pollution hours, whether your home or office has good filtration, and how often AirNow alerts force changes in routine.
Why does cumulative exposure matter for health?
For PM2.5 in particular, dose-response research from the World Health Organization, EPA, and the American Lung Association links long-run exposure to measurable increases in cardiovascular disease, respiratory illness, low birth weight, and pollution-attributable mortality. Year-to-year variability matters less than the multi-year average — which is why a long-tenure resident of a high-AQI city often shows different baseline lung function than a long-tenure resident of a low-AQI city.
Is the dominant pollutant in my city the only one I'm exposed to?
No — every city has multiple pollutants present. The "dominant pollutant" label flags whichever contaminant most often drives the daily AQI category in EPA AQS records. PM2.5, ozone, NO2, PM10, CO, and SO2 are all measured at federally certified monitors. The composite AQI on which this estimator is based reflects the worst single-pollutant reading on each day, so cumulative exposure to a mix of pollutants is implicitly captured even if only one is named.
How can I reduce ongoing exposure?
Three high-leverage steps: (1) sign up for hyperlocal AirNow alerts; (2) run a HEPA air cleaner sized to a bedroom or family room — well-sized indoor HEPA cuts indoor PM2.5 by 80%+ during smoke or pollution episodes; (3) use N95/KN95 masks for outdoor activity on flagged days. The cleanest-air-cities ranking shows where U.S. air runs reliably below the national average for those considering relocation as a long-term mitigation.
Where does the underlying data come from?
Every AQI number is from the EPA Air Quality System (AQS) Annual AQI by County dataset, which aggregates measurements from federally certified monitors. AirHistory processes that data into per-city profiles. EPA AirNow publishes the same network's daily readings; the long historical archive is at aqs.epa.gov/aqsweb/airdata. World Health Organization air-quality guidelines provide the dose-response context used to interpret these numbers.
Personal exposure estimator — cumulative AQI exposure proxy from EPA AQS Annual AQI by County data covering 1,020 U.S. cities.