AQMD Begins Reporting Daily Ozone Levels Using
New Federal 8-Hour Ozone Standard

As Smog Season Begins

Starting today, Southland air pollution officials will begin forecasting and reporting daily ozone air quality using a more stringent federal air quality standard that could lead to an increase in the number of unhealthful days forecast.

“Although our air quality is improving, the new standard is more health protective and could lead to more unhealthy days recorded in the Southland,” said William Burke, Ed.D., Chairman of the South Coast Air Quality Management District.  “This just underscores the importance of moving forward with aggressive measures to clean up Southland air and protect public health.”

The new 8-hour ozone air quality standard, adopted by the U.S. Environmental Protection Agency (EPA) on March 12, is slightly more stringent than the old standard adopted in 1997.  The new standard is 0.075 parts per million (ppm), slightly lower than the old standard of 0.084 ppm.

During smog season, which began on May 1 and ends on Oct. 31, there will likely be more days when air quality exceeds the new standard.  For example, the region exceeded the old 8-hour ozone standard on 79 days in 2007 compared to 109 days in 2007 using the new standard.

As part of the new standard, EPA also lowered the ozone concentrations that correspond to color-coded air quality conditions in the national Air Quality Index (AQI).  This could cause an increase in the number of days when air quality is forecast to reach the “unhealthy for sensitive people” and “unhealthy” ranges.  (See following table)

An AQI value of 100 corresponds to the national air quality standard set for a particular pollutant, in this case ozone.  An AQI value below 100 is generally considered to have minimal adverse health impacts for all but the most sensitive populations.

AQMD is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.

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