U.S. County AirData 5-Year Emission Trends

Sensitivity-gated 5-year change classification for 994 US counties, derived from EPA AirData annual AQI summaries 2020-2024. Counties below the facility-count floor (368) and 4 petrochemical-corridor counties surface as display-held with explicit reason codes rather than silent omission. Methodology underwent a 4-agent legal pre-build review (FTC compliance + defamation/stigmatization + statistical methodology + feeds feasibility) per ZipCheckup Trend Layers v1. Source: EPA AirData annual_aqi_by_county_{YEAR}.zip, years 2020-2024. License: CC BY 4.0 — attribution required.