SO2 Final Rule Scheduled For June 2

EPA is scheduled to release its final rule for the primary sulfur dioxide (SO2) air standard by June 2, 2010. That may mean some counties in your region will no longer be in compliance and need to take new pollution control measures.

SO2 is one of the six "criteria" air pollutants that are considered key indicators of various types of air pollution. The primary standard is intended to protect human health.

The proposed rule was announced Nov. 17, 2009, and posted in the Federal Register on Dec. 8, 2009.

• EPA press release.
• "Proposed Rule: Primary National Ambient Air Quality Standard for Sulfur Dioxide," Federal Register, December 8, 2009, pp. 64810=64881 (Docket No. EPAHQOAR20070352).
• EPA main page for SO2.

The Office of Management and Budget began reviewing the final rule on May 5, 2010.

• Review of the Primary National Ambient Air Quality Standard for Sulfur Dioxide.

Outside observers such as Clean Air Watch's Frank O'Donnell, 202-302-2065, anticipate that the final rule may be at the upper end of the proposed range of 50-100 parts per billion over a one-hour period. The new standard likely will be substantially different in form from the current standard, which addresses 24-hour and annual periods.

• Current criteria air pollutant standards.

When it releases the final rule, EPA likely will provide basic information on the number of counties that could be out of compliance when the rule would go into effect (with such timing to be announced with the final rule). Very few counties are out of compliance with the current standard:

• Sulfur dioxide nonattainment information.

However, since the new standard will likely be based on criteria different than those currently in effect, areas that may violate the new standard could be quite different from today's nonattainment counties.

One way to get a feel for areas with elevated SO2 is to review the data provided by the National Atmospheric Deposition Program (NADP). In general, the eastern half of the US (particularly the swath including IL, IN, OH, WV, PA, NY, NJ, CT, MA, DE, MD, VA, KY, TN, AL, GA, SC, and NC) and Puerto Rico have more elevated concentrations. But keep in mind that this data is somewhat generalized, due to the limited number of monitors. Other hotspots show up on the nonattainment map noted above.

• NADP (select NTN network, Deposition map type, SO4 analyte, and check the last 5 years to account for vagaries such as weather).

Another way to identify possible trouble spots is to check for substantial SO2 emitters in areas of interest to your audience. A quick way to do this is via an EPA site.

• EPA Air Data, Select Geographic Area (select the geographic area(s) of interest, under "Criteria Air Pollutants Emissions Maps" select "Facility Emissions," select SO2, and on the generated map, run your cursor over any of the colored dots to get detailed numbers, keeping in mind that this is 2002 data).

Another important consideration may be a substantial expansion of the monitoring network in order to better capture short-term peaks. As of 2008, there were just 479 monitors for the entire country.

• Monitor Locator Map — Criteria Air Pollutants, or begin here, select United States, under "Criteria Air Pollutant Monitoring Maps," select "Monitor Locator," and select SO2).

Current climate change legislation may be a vehicle for helping to reduce SO2, since some legislators are trying to incorporate language addressing reduction of pollutants tied to energy generation, including SO2, nitrogen oxides, and mercury. If you want to see where these contaminants are elevated, check the NADP data noted above, but select the MDN network for mercury, or the NTN network and the NO3 and NH4 analytes for nitrogen sources. The EPA site for air pollution data by geographic area noted above can also be used to pinpoint substantial nitrogen oxides emitters.

For more information on SO2, see the TipSheet of July 22, 2009.