Insights: Nashville-Davidson--Murfreesboro--Franklin, TN metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 50 over 274 measured days in 2025, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 140 Good days (51%), 133 Moderate (49%), and 1 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 67 while the highest single-day reading hit 136 (USG). Metro residents averaged roughly 15.3 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -38 and the median AQI moved -1 points, which classifies the multi-year trajectory as stable. The metro avoided any Unhealthy-tier days entirely, an outcome that typically reflects favorable wind patterns, lower industrial density, or effective regional emission controls. Metros with comparable AQI profiles include Birmingham-Hoover, AL (51.9% good, AQI 50); Boulder, CO (50.9% good, AQI 50); Durango, CO (53.3% good, AQI 50).