A new rule for sulfur dioxide (SO2) set by the Environmental Protection Agency (EPA) on Thursday sets a new one-hour health standard, changes monitoring requirements, and modifies the Air Quality Index. Full implementation of revised primary National Ambient Air Quality Standard (NAAQS) for SO2 by 2020 could cost the electric power industry nearly $700 million a year, the agency said.

The final rule 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 review to be completed in 2012.

The agency revoked the previous standards, 40 ppb evaluated over 24 hours and 30 ppb evaluated over a year, and set a 1-hour health standard at 75 parts per billion (ppb) instead. The level is designed to protect against short-term exposures ranging from five minutes to 24 hours. The 24-hour and annual health standards were reconsidered because “science indicates that short-term exposures are of greatest concern and the existing standards would not provide additional health benefits,” the EPA said.

New monitoring requirements mandate that monitors be placed where SO2 emissions impact populated areas. States will need to make adjustments to the existing monitoring network in order to ensure that monitors meeting the network design regulations for the new 1-hour SO2 standard are sited and operational by January 1, 2013. The EPA plans to use modeling as well as monitoring to determine compliance with the new standard.

The final rule also changes the Air Quality Index to reflect the revised SO2 standard. This change will improve states’ ability to alert the public when short-term SO2 levels may affect their health. Areas not meeting the new standard will be identified and designated by June 2012.

Total costs to implement the new rule by 2020 could reach to $150 billion, the agency said, but in a regulatory impact analysis (RIA) submitted as part of the proposed rule, it estimated that annualized costs under the 75 ppb final standard in 2020 for the electric power sector could reach $700 million a year.

Responding to a comment regarding the increased cost of power to cooperative consumer-owners—particularly because they have a disproportionate amount of fossil-fuel fired generation when compared to the power sector as a whole—the EPA said that the electric power industry “will only experience annualized costs of less than 0.4 percent of total industry revenues in 2020.”

It added: “While we do not provide impacts for individual power plants and their owners, the impact estimates do suggest that, at a broad scale, the electric power industry, as affected by illustrative control strategies such as those included in this RIA, will not experience substantial impacts from compliance with this NAAQS.”

The first NAAQS for SO2 were last set in 1971, establishing both a primary standard to protect health and a secondary standard to protect the public welfare. According to the EPA, annual average SO2 concentrations have dropped 71% since 1980.

The Clean Air Act requires the EPA to set national ambient air quality standards for what it calls “criteria pollutants.” Currently, sulfur oxides and five other major pollutants are criteria pollutants: ozone, lead, carbon monoxide, nitrogen oxides, and particulate matter. The law also requires the EPA to review the standards periodically and revise them if appropriate to ensure that they provide requisite health and environmental protection, and to update those standards as necessary.

Sources: EPA, POWERnews