EPA annual release diff · 2024–2025

Which counties changed between the last two EPA annual releases?

Like-for-like Good-day share for counties monitored at least 200 days in both 2024 and 2025. Every figure is computed from two stored EPA annual rows, not a live advisory and not a cause claim.

396
counties improved ≥1pp
351
counties declined ≥1pp
+0.8pp
average county change

Among 896 comparable counties, 149 moved by less than one percentage point. Source refresh checked August 2026. For the longer 2020–2025 window see national trends, most improved, and biggest declines.

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Largest Good-day share gains (2024–2025)

Percentage-point increase in days rated Good

  1. 1 Colusa, California 60.6pp
  2. 2 Cobb, Georgia 38pp
  3. 3 Shelby, Tennessee 25.8pp
  4. 4 Durham, North Carolina 25.3pp
  5. 5 Meade, South Dakota 24.8pp
  6. 6 Carter, Oklahoma 21.9pp
  7. 7 Bossier, Louisiana 21.5pp
  8. 8 San Benito, California 20.5pp
  9. 9 Atascosa, Texas 18.9pp
  10. 10 Boise, Idaho 18.8pp
  11. 11 Deschutes, Oregon 18.8pp
  12. 12 Polk, Florida 18.2pp

Good-day share change · EPA Air Quality System

Largest gain: Colusa, California (18.6% → 79.2%, +60.6pp).

Largest Good-day share declines (2024–2025)

Percentage-point decrease in days rated Good; bar length = magnitude

  1. 1 Monroe, Wisconsin 22pp
  2. 2 Brookings, South Dakota 21.2pp
  3. 3 Bonner, Idaho 18.4pp
  4. 4 Davidson, North Carolina 18pp
  5. 5 Sedgwick, Kansas 17.6pp
  6. 6 Ouachita, Louisiana 17.6pp
  7. 7 Jackson, Wisconsin 16.9pp
  8. 8 New York, New York 15.7pp
  9. 9 Lee, Florida 15.6pp
  10. 10 Tuscaloosa, Alabama 15pp
  11. 11 Oxford, Maine 13.7pp
  12. 12 Apache, Arizona 13.2pp

Good-day share decline · EPA Air Quality System

Largest decline: Monroe, Wisconsin (89.6% → 67.5%, -22pp).

Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. Release diffs are computed from stored EPA annual county rows; no cause is attributed. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.