Natural Resources Defense Council, Inc. v. United States Environmental Protection Agency

Maryland and Virginia set their respective water-quality standards to allow dioxin to be present in state waters in the amount of 1.2 parts per quadrillion (ppq), which was less than the .0013 ppq guidance criterion of the Environmental Protection Agency (EPA) (defendant). Dioxin was a potentially carcinogenic chemical compound. The states based their water standard for dioxin on the Food and Drug Administration (FDA) cancer-potency factor for dioxin and evidence supporting that the EPA was overestimating the compound’s carcinogenic potential. The EPA approved Maryland and Virginia’s standards as scientifically defensible, protective of human health, and fully compliant with the Clean Water Act (CWA). The Natural Resources Defense Council (NRDC) and Environmental Defense Fund (EDF) (plaintiffs) sued the EPA, challenging the EPA’s approval of the states’ water-quality standard for dioxin. The district court ruled in the EPA’s favor. NRDC and EDF appealed, arguing in essence that Maryland and Virginia’s lower-than-federal-guidance water-quality standard was improperly approved. NRDC and EDF specifically asserted that the states’ standard underestimated certain people’s quantity of fish consumption; used an outdated bioconcentration factor, referring to the higher concentration of dioxin in fish fat than in water; and was insufficiently protective of aquatic life and wildlife.