EPA is proposing stronger air quality standards for Sulfur Dioxide emissions (SO2) that are more health protective, as opposed to being technologically based. The proposal also establishes a new national 1-hour monitoring standard, and revokes the current 24- hour and SO2 annual health standards. The Center participated in the EPA conference call to discuss the new SO2 standardsPeople with asthma, children, and the elderly areespecially vulnerable to SO2’s effects. This new proposal is to establish a new national one-hour SO2 standard, between 50 and 100 parts per billion (ppb). This standardis designed to protect against short-term exposures ranging from five minutes to 24 hours. Monitors would be placed in areas with high SO2 emission levels as well as in urban areas. The proposal also would change the Air Quality Index to reflect the revised SO2 standards.
The Agency first set National Ambient Air Quality standards for SO2 in 1971. EPA set a 24-hour primary standard at 140 ppb and an annual average standard at 30 ppb (to protect health). EPA also set a 3-hour average secondary standard at 500 ppb (to protect the public welfare).
The last review of the SO2 NAAQS was completed in 1996 and the Agency chose not to revise the standards. In the last review, EPA also considered, but did not set, a five minute NAAQS to protect asthmatics at elevated ventilation rates from bronchoconstriction and respiratory symptoms associated with 5-10 minute peaks of SO2.
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