![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
AnnouncementsAugust 17, 2011 - EPA will hold public hearing on proposal for secondary standards for oxides of nitrogen and sulfur. July 12, 2011 EPA Proposes Update to NOx and SOx Secondary Standards June 2, 2010 - EPA strengthens the primary air quality standard for sulfur dioxide.
|
Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as “oxides of sulfur.” The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%). Smaller sources of SO2 emissions include industrial processes such as extracting metal from ore, and the burning of high sulfur containing fuels by locomotives, large ships, and non-road equipment. SO2 is linked with a number of adverse effects on the respiratory system.
EPA first set 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.
For more information about SO2:
Basic Information - Basics about SO2 air pollution.
Health - Effects of SO2 air pollution.
SO2 Primary Standards - Links to technical information related to setting the national air quality standards for SO2 to protect public health.
SO2 Secondary Standards - Links to technical information related to setting the national air quality standards for SO2 to protect public welfare.
SO2 Implementation - Programs and requirements for reducing SO2 air pollution.
Regulatory Actions - Links to proposed and final rules, fact sheets, and other rulemaking documents.
Policy and Guidance - Links to policies and guidance on SO2 designations and implementation.
Nonattainment Areas - Status of nonattainment areas (the Green Book)
Air Quality Trends - Progress made in reducing SO2 in the air.
Air Emission Sources - Summarizes SO2 air emissions by source at national, state and local levels.