A Review of the Most Frequent Compounds, Metals, and Compound and Metal Mixtures Found at U.S. Superfund Sites and Their Carcinogenic Potential.

The United States Environmental Protection Agency's (U.S. EPA) National Priorities List (NPL) is a list of sites in the U.S. and its territories of national priority that are sources of known hazardous contaminants, pollutants, or substances that pose a significant risk to human health and the environment. These sites are commonly termed U.S. Superfund sites and contain many harmful compounds and metals. This paper reviews the carcinogenic potential of the most frequent compounds, metals, and mixtures at U.S. Superfund sites. Of the most frequent compounds and metals identified at U.S. Superfund sites, some are classified as human carcinogens and some as probable/possible human carcinogens. The most frequent mixtures of three individual carcinogenic compound or metals at U.S. Superfund sites include: nickel, arsenic, and cadmium (496 sites); benzene, arsenic, trichloroethene (451 sites); benzene, vinyl chloride, trichloroethene (420 sites); and arsenic, vinyl chloride, trichloroethene (386 sites). Many compounds or metals that are frequently found at U.S. Superfund Sites have not been evaluated for carcinogenic activity because of limited data including copper, xylene, mercury, barium, and iron. Factors in human cancer development include both environmental factors and genetic disease susceptibility backgrounds. Thus, future mixture toxicology studies should be conducted with a design that looks at mixture toxicology in a variety of models with varied genetic backgrounds.