Abstract

Halogenated hydrocarbons such as the polychlorinated biphenyls (PCBs), hydroxy-PCBs, polybrominated diphenyl ethers (PBDEs), polychlorinated naphthalenes (PCNs), and chlorinated insecticides (lindane) have been widely used industrial compounds. These chemicals are lipophilic and their release into the environment results in bioaccumulation in adipose tissue and persistence due to their chemical stability and resistance to metabolic breakdown. Thus, the more widely used PCBs and lindane have been identified in almost every component of the global ecosystem including fish, wildlife, and humans. Risk and hazard assessment of the highly complex halogenated hydrocarbon mixtures is difficult; however, at least one subgroup of chemicals within these mixtures can be evaluated. Several PCB congeners exhibit aryl hydrocarbon receptor (AhR) agonist activities and their potencies relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been determined and used to calculate TCDD or toxic equivalents (TEQs) for various mixtures. However, risk assessment of most other halogenated hydrocarbons is not well defined and requires further research to determine their activities and relative potencies.