Louisiana Air Quality Rankings
County-level AQI rollup using EPA Air Quality System monitor records. Refreshed as new EPA AQS data lands.
County-by-county air quality data for Louisiana based on EPA AQS annual AQI readings. Data covers 22 monitored counties for 2024.
Louisiana (2024): 22 counties monitored. State average median AQI: 42 (national average: 38.8). 70% of monitored days rated "Good." Most unhealthy air: Ascension Parish County (1 days above AQI 100).
Louisiana air quality on this page is drawn from the EPA Air Quality System (AQS), which aggregates daily readings from federal, state, tribal, and local monitors into annual summaries per county for 2024, the current dataset's reporting year (county coverage and the state/national average shown above).
The heaviest burden of unhealthy days lands on Ascension Parish County (1 day above AQI 100), while St. James Parish County records the cleanest air with a median AQI of 32.
AQI values translate ambient concentrations of pollutants (ozone, PM2.5, PM10, NO₂, SO₂, CO) onto a single 0–500 scale with six health-based bands. A low median AQI reflects typical daily conditions; peak values matter separately because short-term exposure drives most acute health effects. Counties without monitors are not "clean" - they are simply unmeasured by EPA AQS. For site-specific exposure guidance, check AirNow.gov alongside the county detail links below.
Which Louisiana counties have the worst air quality?
Ranked by median AQI (higher = worse). Click a county for full environmental data.
| # | County | Median AQI | Unhealthy Days |
|---|---|---|---|
| 1 | Lafayette Parish | 51 | 0 |
| 2 | East Baton Rouge Parish | 51 | 1 |
| 3 | Calcasieu Parish | 49 | 0 |
| 4 | West Baton Rouge Parish | 49 | 0 |
| 5 | Lafourche Parish | 48 | 0 |
| 6 | Tangipahoa Parish | 47 | 0 |
| 7 | Bossier Parish | 47 | 0 |
| 8 | Jefferson Parish | 46 | 1 |
| 9 | St. Bernard Parish | 45 | 0 |
| 10 | Livingston Parish | 44 | 0 |
| 11 | Orleans Parish | 41 | 0 |
| 12 | Iberville Parish | 41 | 1 |
| 13 | Caddo Parish | 41 | 0 |
| 14 | Ouachita Parish | 41 | 0 |
| 15 | Terrebonne Parish | 39 | 0 |
| 16 | St. Tammany Parish | 39 | 1 |
| 17 | Rapides Parish | 39 | 0 |
| 18 | St. Martin Parish | 38 | 0 |
| 19 | St. John The Baptist Parish | 36 | 0 |
| 20 | Pointe Coupee Parish | 36 | 0 |
| 21 | Ascension Parish | 33 | 1 |
| 22 | St. James Parish | 32 | 0 |
Frequently Asked Questions
What is the air quality like in Louisiana?
In 2024, Louisiana had an average median AQI of 42 across 22 monitored counties, with 70% of monitored days rated "Good" (AQI 0–50). The national average median AQI is 38.8.
Which county in Louisiana has the worst air quality?
Based on 2024 EPA AQS data, Ascension Parish County had the most unhealthy air days in Louisiana - 1 days above AQI 100, with a median AQI of 33.
About This Data
Air quality data is from the EPA Air Quality System (AQS), Annual AQI by County dataset. Counties with fewer than 10 monitored days are excluded. "Unhealthy days" counts days with AQI above 100 (Unhealthy for Sensitive Groups or worse). All data is for 2024.
Source: U.S. Environmental Protection Agency, Air Quality System (AQS)
Read our methodology - how this data is sourced, computed, and verified.