From: Roger Greenway, ENN
Published November 18, 2009 07:10 AM

USEPA Proposes One — Hour Sulfur Dioxide Standard, to Drop 24 -hr and Annual Primary Standards

The US Environmental Protection Agency has proposed a new one — hour Sulfur Dioxide (SO2) standard. The SO2 standard has not been changed since 1971. There has not been a primary (health based standard) shorter than 24 hrs for SO2 since short term acute effects have not been well known. A secondary standard of 3-hrs has been in effect. This was set to address welfare considerations, not health.

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Current scientific evidence links short-term exposures to SO2, ranging from 5 minutes to 24 hours, with an array of adverse respiratory effects including bronchoconstriction and increased asthma symptoms. These effects are particularly important for asthmatics at elevated ventilation rates (e.g., while exercising or playing.)

Studies also show a connection between short-term exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations including children, the elderly, and asthmatics.

EPA is taking comment on a proposal to establish a new national one-hour SO2 standard, between 50 and 100 parts per billion (ppb). This standard is designed to protect against short-term exposures ranging from five minutes to 24 hours. Because the revised standards would be more protective, EPA is proposing to revoke the current 24-hour and annual SO2 health standards.

EPA also is proposing changes to monitoring and reporting requirements for SO2. 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. This change would improve states’ ability to alert the public when short-term SO2 levels may affect their health.

The proposal 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 proposal in 2011.

The public comment period will be open for 60 days after the proposal is published in the Federal Register. The agency will hold a public hearing on Jan. 5, 2010 in Atlanta and will issue final standards by June 2, 2010.

For more information: http://yosemite.epa.gov/opa/admpress.nsf/0/F4DCB340A6D523608525767100770756

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