EPA is setting the one-hour sulfur dioxide (SO2) health standard at 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.


EPA is also changing the monitoring requirements for SO2. The new requirements assure 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 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.

More information: http://www.epa.gov/air/sulfurdioxide