Is the Air Quality Good in Lancaster, Pennsylvania?
Mostly — air quality in Lancaster, Pennsylvania is fair, not pristine. The city earns a Grade of C (fair) on a 5-year median AQI of 55 (Moderate), with 44 unhealthy-air days over five years (about 9 per year). Healthy adults are fine most of the time, but sensitive groups should watch the daily forecast.
Who Can Safely Breathe the Air in Lancaster, Pennsylvania?
Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
Across the past five years, this area has logged 44 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 9 days per year. That is roughly typical for a U.S. metro, with most caution days clustered in summer (ozone) or wildfire season.
Lancaster, Pennsylvania Air Quality Snapshot
| Air Quality Grade | C55/100 |
| 5-Year Median AQI | 55 (Moderate) |
| Most Recent Median AQI (2023) | 58 (Moderate) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Stable (-0.11 AQI/yr) |
| Unhealthy Days (last 5 yr) | 44 |
| National Rank (cleanest = #1) | #993 of 1,020 (97th most polluted percentile) |
| Pennsylvania Rank | #39 of 40 |
What Does the C Grade Mean?
Lancaster, Pennsylvania earns a C — air quality is fair, but not great. With a 5-year median AQI of 55, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.
Lancaster, Pennsylvania's 5-year median AQI of 55 is 14 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within Pennsylvania, Lancaster, Pennsylvania runs more polluted than the state average of 43 — local sources or geography are concentrating pollution above the state's typical reading.
For context within Pennsylvania: Wyoming, Pennsylvania currently holds the state's cleanest grade (A, AQI 33), while Allegheny, Pennsylvania sits at the bottom (C, AQI 56).
What's in Lancaster, Pennsylvania's Air?
The dominant pollutant in Lancaster, Pennsylvania is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 304 | 83% |
| Ground-Level Ozone | 61 | 17% |
Is the Air Getting Better or Worse?
Air quality in Lancaster, Pennsylvania has held roughly steady over the past decade, with year-to-year shifts in median AQI of less than half a point. That stability makes the city's long-run grade a reliable signal of what residents can expect day-to-day.
In 2014, Lancaster, Pennsylvania posted a median AQI of 61. By 2023 that figure was 58 — a drop of 3 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Lancaster, Pennsylvania
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 61 | 58 | 15 | PM2.5 |
| 2015 | 56 | 121 | 10 | PM2.5 |
| 2016 | 56 | 117 | 6 | PM2.5 |
| 2017 | 55 | 122 | 4 | PM2.5 |
| 2018 | 52 | 167 | 5 | PM2.5 |
| 2019 | 52 | 160 | 10 | PM2.5 |
| 2020 | 51 | 177 | 5 | PM2.5 |
| 2021 | 56 | 100 | 8 | PM2.5 |
| 2022 | 59 | 84 | 7 | PM2.5 |
| 2023 | 58 | 108 | 14 | PM2.5 |
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
More about Lancaster, Pennsylvania
Lancaster, Pennsylvania has an Air Quality Grade of C (fair) with a 5-year median AQI of 55. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been stable over the past decade.
This answer pulls from the EPA Air Quality System (AQS), the authoritative federal source for U.S. air quality and pollution monitoring. The headline number above is the direct answer; what follows is the additional context most readers need to use the answer for a real decision rather than just a fact lookup.
A practical caveat: the headline answer above reflects the most recent the EPA Air Quality System (AQS) vintage; underlying data is often revised for months after first publication, and the right reference for any specific decision is whichever vintage is current at the time of the decision. The as-of date is stamped on every page.
Source: EPA Outdoor Air Quality Data, 2026.