The U.S. Environmental Protection Agency has asked for comments on three proposed alternatives aimed at giving the public more protection from acute, short term exposure to sulfur dioxide.
In the meantime, the agency plans to retain current ambient (atmospheric) air quality standards for S02 After reviewing health studies, the agency found ambient S02 levels dropped 26% during 1984-93. EPA reminded that SO2 can cause respiratory illness.
It pointed out that ambient S02 results mainly from combustion and processing of fuels and ores that contain sulfur. Sources include lead and copper smelters, pulp and paper mills, refineries, certain industrial boilers, and power plants.
ALTERNATIVES
EPA's first proposed alternative would add a stricter, short term, primary S02 standard. Primary standards are designed to protect public health.
The new short term standard would be 0.6 ppm of ambient air concentrations Of S02 averaged during a 5 min period and could not be exceeded on average more than once a year.
The second alternative would supplement existing standards by having states administer a new regulatory program setting a "trigger" level of 0.6 ppm averaged over a 5 min period. Once the trigger level was violated, states would work with sources to correct the violation.
The third alternative would focus air monitoring activities on sources likely to produce high short term levels of SO, emissions. It would ensure that these sources meet existing standards and applicable good operating practices.
EPA soon will propose a rule specifying how each of the three proposed alternatives will be implemented.
CURRENT STANDARDS
EPA has two primary standards for SO2 at present.
One measures ambient air concentrations averaged over 24 hr, set at 0.14 ppm. The other is an annual average set at 0.03 ppm.
The agency also is required to set a secondary standard to protect public welfare from the effects of the pollutant on vegetation. The current S02 secondary standard is 0.5 ppm averaged over a 3 hr period and not to be exceeded more than once a year.
EPA decided last year not to revise the secondary standard.
The agency has four programs to control S02 emissions:
- The acid rain program to reduce power plant S02 emissions 10 million tons/year by 2010.
- The new source performance standards program, which sets direct federal emission standards for new sources such as utilities and smelters.
- The new source review/prevention of significant deterioration program which protects air quality from slipping in clean air areas.
- A program to help local areas attain and maintain the ambient air standard for S02.
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
Issue date: 11/21/94
