Sierra Club v. Environmental Protection Agency

The Environmental Protection Agency (EPA) (defendant) promulgated two phases of emission standards according to Section 112 of the Clean Air Act (CAA) to regulate the emission of hazardous air pollutants (HAPs). The first phase required the EPA to establish standards based on the maximum achievable control technology (MACT). The EPA established a MACT floor, which was the minimum level of reduction required by the statute. The EPA could then impose stricter standards called beyond-the-floor limits after considering costs and non-air quality health and environmental impacts and energy requirements. The second phase occurred eight years after the first phase and required the EPA to consider what residual risks remained and whether more stringent MACT standards were required to protect public health. The process of copper smelting produced exhaust gas that was subject to EPA regulations. The exhaust gas, or off-gases, contained lead and arsenic that were released in the form of particulate matter (PM) as HAPs. The EPA surveyed the use of PM control technology by copper smelters. The EPA, after determining that copper smelters used PM control devices to reduce HAP emissions, set standards for HAP emissions in terms of PM rather than setting limits for each HAP. The Sierra Club (plaintiff) challenged the EPA’s regulations and petitioned for review in district court, alleging that the EPA refused to consider non-air quality health and environmental impacts as required by the CAA. The Sierra Club argued that the EPA was required to consider the impacts of HAP emissions that were not directly delivered through the air, but through other means, such as by deposition. The EPA argued that non-air quality impacts referred to the impacts that may result from efforts to control the air quality impacts of the underlying manufacturing process.