The Occupational Safety and Health Act of 1970 (Act) delegated authority to the Secretary of Labor to promulgate standards to ensure safe and healthful working conditions. According to Section 3(8), standards created by the secretary must be “reasonably necessary or appropriate to provide safe or healthful employment and places of employment.” Section 6(b)(5) of the statute sets the principle for creating the safety regulations, directing the Secretary to “set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity. . . .” Pursuant to this Act, the Secretary promulgated a standard to regulate exposure to benzene, a carcinogen. The Secretary took the position that no safe exposure level can be determined and that § 6(b)(5) requires him to set an exposure limit at the lowest technologically feasible level that will not impair the viability of the industries regulated. The American Petroleum Institute (plaintiff) took the issue to court, and the Court of Appeals for the Fifth Circuit held the regulation invalid. The Supreme Court granted certiorari.