The EPA last week proposed to strengthen the primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (SO2). The new rule is the first time EPA has tightened controls for SO2 since 1971.

Specifically, the EPA proposes to replace the existing annual and 24-hour primary SO2 standards with a new 1-hour SO2 standard and set a level between 50 and 100 parts per billion (ppb).  The proposed standard does not address the secondary SO2 standard, which the EPA is currently reviewing separately as part of a joint review of the welfare effects associated with SO2 and NO2 (expected to be completed in 2012).

The Clean Air Act requires EPA to set two types of national ambient air quality standards for “criteria” air pollutants. The primary standards protect public health, while secondary standards protect public welfare and the environment.

The rules are aimed at coal-fired power plants and other sources that produce SO2, such as industrial plants, locomotives, ships, and non-road equipment.

The proposed rule is the latest move by the current Administration to dramatically increase air quality regulations. Since taking office, the Obama Administration proposed mandatory greenhouse gas reporting regulations. In addition, the Administration issued proposed rules proposing to find that greenhouse gases endanger the public health and welfare, which could ultimately lead to the EPA regulating CO2 under the Clean Air Act. In addition, the EPA is currently reconsidering the 2008 8-hour ozone standard.

Hamilton Consulting will provide continuous updates on each of the proposed regulations.