The environmental laws enacted by Congress shape EPA’s regulatory structure, which, in turn, influence EPA risk-assessment practices and perspectives. The statutes give EPA authority to regulate many forms of pollution (for example, pesticides, solid wastes, and industrial chemicals) as they affect different aspects of the environment (for example, air quality, water quality, human health, and plant and animal wildlife). The premise central to EPA risk-assessment practices can be found in enabling legislation for its four major program offices: air and radiation, water, solid waste and emergency response, and prevention, pesticides, and toxic substances. Selected provisions appear below.

  • The Clean Water Act calls for standards “adequate to protect public health and the environment from any reasonably anticipated adverse effects” (CWA § 405 (d)(2)(D)).

  • The Clean Air Act, when addressing criteria pollutants, directs the agency to develop criteria “reflecting the latest scientific knowledge” and, on the basis of those criteria, to issue “national primary ambient air quality standards to … protect public health with an adequate margin of safety” (CAA §§ 108,109).

  • The primary purpose of the Toxic Substances Control Act is “to assure [that technologic] innovation and commerce in such chemical substances and mixtures do not present an unreasonable risk of injury to health or the environment” (TSCA § 2 (b)(3)).

  • Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), one criterion for registering (licensing) a pesticide is that “it will perform its intended function without unreasonable adverse effects on human health and the environment” (FIFRA § 3).

  • The Superfund National Contingency Plan specifies that “criteria and priorities [for responding to releases of hazardous substances] shall be based upon relative risk or danger to public health or welfare or the environment” (CERCLA § 105 (a)(8)(A)).

The term risk assessment does not appear often in the statutes, and it is important to note that these statues were enacted prior to the emergence of risk analysis as an integrative discipline in the late 1970s and early 1980s. Rather, EPA risk-assessment principles and practices stem from statutory provisions calling for information on “adverse effects” (EPA 2004a, p. 14), “relative risk” (p. 82), “unreasonable risk” (p. 14), and “the current scientific knowledge” (p. 104) and for regulatory decisions on protecting human health and the environment. The statutes provide various standards and procedures related to the scientific analyses used to evaluate the risk potential of pollutants subject to the statutes.1,2


Different emphases and terminology lead to different risk-assessment approaches, sometimes for the same pollutant, in different agency programs. That can confuse and confound observers. For example, Clean Air Act provisions related to four air-pollution topics use different terms for what is essentially the same statutory finding:

• Clean Air Act provisions related to pollutants regulated as national ambient air quality standards are designed to “protect the public health with an adequate margin of safety” (CAA § 109, emphasis added).

• For welfare (environmental) effects, this provision directs the office to “protect the public welfare from any known or anticipated adverse effects” (CAA § 109, emphasis added).

• Standards for “hazardous” pollutants from stationary sources (for example, factories) are to “provide an ample margin of safety to protect public health or prevent an adverse environmental effect” (CAA § 112, emphasis added).

• Regarding mobile sources (for example, cars), the statute calls for ensuring that these vehicles do not “cause or contribute to an unreasonable risk to public health, welfare or safety” (CAA § 202 (a)(4), emphasis added).


Some statutes call for technology-based standards that require, for example, specific control techniques or technology-forcing standards that specify emission limits to be achieved within given periods. Such standards are based on costs, engineering feasibility, and related technical considerations. Examples include Clean Air Act Sections 111 (new-source review) and 202 (mobile-source emissions).

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