Air Quality
Good
Water Violations
8
Active Contamination
3
Active Permits
4
Air quality in McHenry County is rated good with a median AQI of 43 (272 days measured in 2025). 1 community water system serve the area, with 8 recent violations in the last 5 years. 2 industrial facilities report toxic chemical releases totaling 2.3K lbs. 9 contamination sites are tracked, all with completed or ongoing remediation.
Air Quality — McHenry County (2025)i
AQSThe Air Quality Index measures how clean or polluted the air is on a given day. AQI is reported at the county level. A score of 0-50 is considered good; 51-100 is moderate; above 100 may be unhealthy for sensitive groups.
Median AQI
PM2.5 Daysi
118Ozone Daysi
154Drinking Wateri
SDWISPublic water systems registered to serve this area. Community systems (CWS) provide water to residents year-round. Violations indicate a system failed to meet federal drinking water standards.
Community Systemsi
1Active Systemsi
2Recent Violationsi
8Recent Violations (Last 5 Years)
UNION
Industrial Monitoringi
Toxic Release Inventory (TRI)i
TRIContamination Sitesi
Contaminated sites tracked by the EPA and state agencies. Superfund sites are the most seriously contaminated locations. Brownfields are former industrial properties being cleaned up for reuse. LUST sites have confirmed leaks from underground storage tanks.