| The U.S. Environmental Protection Agency has established Air Quality
Indices (AQI) for several of the parameters for which there are air
quality standards, but not all of the air quality related parameters
that are measured have a defined AQI. AQI have been established
for the health-related air quality standards, but some of the standards,
such as the 3-hour average sulfur dioxide standard, are based on other
criteria (damage to vegetation). Some air quality parameters
are measured for which there are no AQI and reported on this website in terms of the 1-hour
averaging time. These 1-hour averages are subsequently combined
and used to calculate longer averaging periods relevant to determining
compliance with longer-term air quality standards. |
