Carus Chemical Co. v. Environmental Protection Agency

Carus Chemical Company (plaintiff) operated a manufacturing plant on the Matthiessen & Hegeler Zinc Company Site (M&H Site). The M&H Site had two large slag piles containing various contaminants, including cadmium, that were partially sitting in the adjacent Little Vermilion River. The Environmental Protection Agency (EPA) (defendant) placed the M&H Site on CERCLA’s National Priorities List (NPL), making it a top priority for remedial response to hazardous-substance release. In evaluating the M&H Site for NPL inclusion, the EPA used the toxicity value for cadmium’s inhalation exposure pathway even though inhalation was both the least likely and highest toxicity value pathway. Surface-water migration, which carried a much lower toxicity value, was the more likely pathway for exposure. The EPA stated that the Hazard Ranking System (HRS), which was used to evaluate sites for NPL inclusion, mandated that the HRS analysis must use the highest toxicity value even if the exposure pathway with the highest toxicity value was also the least likely to occur. Carus challenged, arguing that (1) the EPA’s interpretation of the HRS was wrong and that the surface-water pathway should have been used because it was more likely; and (2) the EPA should have used the data collected by M&H in its evaluation rather than the earlier data collected by the Illinois EPA.