SO2 Health Standard Finalized, Set at 75 Parts Per Billion

The U.S. Environmental Protection Agency is issuing a final new health standard for sulfur dioxide (SO2). The one-hour standard will be 75 parts per billion (ppb), a level designed to protect against short-term exposures ranging from five minutes to 24 hours.

EPA is revoking the current 24-hour and annual SO2 health standards because the science indicates that short-term exposures are of greatest concern and the existing standards would not provide additional health benefits.

“We’re taking on an old problem in a new way, one designed to give all American communities the clean air protections they deserve. Moving to a one-hour standard and monitoring in the areas with the highest SO2 levels is the most efficient and effective way to protect against sulfur dioxide pollution in the air we breathe,” said EPA Administrator Lisa P. Jackson. “This is one of many pollutants we’ve been able to significantly reduce through the Clean Air Act, keeping people healthy, protecting our environment and growing our economy. This new standard ─ the first in almost 40 years ─ will ensure continued success in meeting these challenges.”

EPA also is changing the monitoring requirements for SO2. The new requirements ensure that monitors will be placed where SO2 emissions impact populated areas. Any new monitors required by this rule must begin operating no later than Jan. 1, 2013. EPA is expecting to use modeling as well as monitoring to determine compliance with the new standard.

The final rule also changes the Air Quality Index to reflect the revised SO2 standard. This change will improve states’ ability to alert the public when short-term SO2 levels may affect their health.

EPA estimates that the health benefits associated with this rule range between $13 billion and $33 billion annually. These benefits include preventing 2,300 to 5,900 premature deaths and 54,000 asthma attacks a year. The estimated cost in 2020 to fully implement this standard is approximately $1.5 billion.

The first National Ambient Air Quality Standards for SO2 were set in 1971, establishing both a primary standard to protect health and a secondary standard to protect the public welfare. Annual average SO2 concentrations have decreased by 71 percent since 1980.

The final rule addresses only the SO2 primary standards, which are designed to protect public health. EPA will address the secondary standard – designed to protect the public welfare, including the environment – as part of a separate review to be completed in 2012.

EPA expects to identify or designate areas not meeting the new standard by June 2012.

The American Lung Association (ALA) applauded the new standard for SO2. For the first time, this standard will help curtail the bursts of this noxious gas that spew into communities located closest to coal-fired power plants, industrial boilers, petroleum refineries, metal processing plants and diesel exhaust.

SO2 tightens the airways, making it harder for people with asthma, chronic obstructive pulmonary disease and other lung diseases to breathe. It worsens coughing and wheezing and increases asthma attacks. .

ALA said it also appreciated EPA’s decision to make sure that every community is “classified.” In the past, communities without adequate monitoring information could avoid having to clean up because they fit in the “unclassified” category. For the first time, EPA is requiring that these communities use the modeling and monitoring data to show that they are either meeting or failing to meet the standard.

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