The Clean Air Acts of 1963 and 1967 gave to the Environmental Protection Agency (EPA) the authority to establish emission standards for new and modified stationary sources. These standards are called new source performance standards (NSPS) and are determined by the best emission control technology available, the energy needed to use the technology, and its overall cost. An example of an NSPS is the standard set for plants that make Portland cement. Such plants are allowed to release no more than 0.30 pounds of emissions for each ton of raw materials used and to produce an emission with no more than 20 percent opacity.