The federal government has set standards for six outdoor air pollutants, also known as criteria pollutants: carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, particulate, and lead. These pollutants are considered to be the most widespread nationally and the most immediately dangerous to human health.  Communities are required to meet the federal health standards for all six of the criteria pollutants but are only required to continually monitor for those which appear to merit testing in that area as indicated by historical data, trends, and known emissions.

Chattanooga was in compliance with all of the federal health standards from 1989-2004. We are currently out of compliance for particulate and are also taking voluntary measures as part of an Early Action Compact to achieve compliance with ozone. Of the six pollutants, ozone and particulate are the only ones that our county is required to monitor.

The Bureau maintains a network of seven monitoring sites throughout the county.  The Bureau reports the daily air quality using the Air Quality Index, which is a scale designed by the EPA to standardize the method for reporting air quality nationwide.  In Hamilton County, the daily air quality level is determined by either the ozone or the particulate concentration--whichever is higher on that day.

See the Daily Air Quality Report for more information.