On June 3, 2010, the U.S. Environmental Protection Agency [EPA] issued a final rule establishing lowered standards for acceptable levels of sulfur-dioxide [SO2] emissions. The new rule also changes the monitoring requirements for SO2. SO2 is one of six criteria pollutants which Federal agencies must evaluate under the EPA’s General Conformity Rule, to determine whether emissions from a proposed project would conform to an approved CAA implementation plan. If a conformity analysis and determination indicate that a proposed Federal project would not conform to an applicable implementation plan, the project cannot be funded, licensed, permitted or approved.

SO2 is a highly reactive gas often linked to a number of respiratory system problems. People with asthma, children and the elderly are especially vulnerable to the effects of SO2. The largest sources of SO2 emissions are from fossil fuel combustion at power plants and other industrial facilities. The EPA established standards for SO2 emissions in 1971, and reviewed those standards in 1996, but chose not to revise the standards at that time.

Section 109(a) of the Federal Clean Air Act [CAA] directs the EPA Administrator to promulgate “primary” and “secondary” National Ambient Air Quality Standards [NAAQS] for pollutants for which air quality standards have been issued. One such pollutant is oxides of sulfur, as measured by SO2. Primary standards are aimed at protecting public health. Secondary standards are aimed at protecting public welfare, including the environment. The final rule addresses only SO2 primary standards. The EPA will address SO2 secondary standards as part of a separate review to be completed in 2012.

Under the new rule, allowable SO2 levels will be reduced from the current 140 parts per billion [ppb] averaged over 24 hours to 75 ppb measured hourly. The rule requires that monitors be placed where SO2 emissions impact populated areas, and new monitors must begin operating no later than January 1, 2013. The lower SO2 emissions level is designed to protect against short-term exposures ranging from five minutes to 24 hours because, according to the EPA, the science indicates that short-term exposures are of greatest concern. The EPA estimates that the new standards will prevent from 2,300 to 5,900 premature deaths and 54,000 asthma attacks a year, and reduce health care costs by an estimated $13 billion to $33 billion annually.

The new rule will go into effect 60 days after publication in the Federal Register. States will have until June, 2011 to submit implementation plans to the EPA for approval. The final rule is available at www.epa.gov/air/sulfurdioxide/.