Toxicology, structure-function relationship, and human and environmental health impacts of polychlorinated biphenyls: Progress and problems
- Texas A M Univ., College Station, TX (United States)
Polychlorinated biphenyls (PCBs) are industrial compounds that have been detected as contaminants in almost every component of the global ecosystem including the air, water, sediments, fish, and wildlife, and human adipose tissue, milk, and serum. PCBs in commercial produces and environmental extracts are complex mixtures of isomers and congeners that can now be analyzed on a congener-specific basis using high-resolution gas chromatographic analysis. PCBs are metabolized primarily via mixed-function oxidases into a broad spectrum of metabolites. The results indicate that metabolic activation is not required for PCB toxicity, and the parent hydrocarbons are responsible for most of the biochemical and toxic responses elicited by these compounds. Structure-function relationships for PCB congeners have identified two major structural classes of PCBs that elicit [open quotes]TCDD-like[close quotes] responses, namely, the coplanar PCBs (e.g., 3,3[prime]4,4[prime]-tetraCB, D,3[prime]4,4[prime]5-pentaCB and 3,3[prime]4,4[prime]5,5[prime]-hexaCB) and their mono-ortho coplanar derivatives. These compounds competitively bind to the TCDD or aryl hydrocarbon (Ah) receptor and exhibit Ah receptor agonist activity. In addition, other structural classes of PCBs elicit biochemical and toxic responses that are not mediated through the Ah receptor. The short-term effects of PCBs on occupationally exposed humans appear to be reversible, and no consistent changes in overall mortality and cancer mortality have been reported. Recent studies have demonstrated that some developmental deficits in infants and children correlated with in utero exposure to PCBs; however, the etiologic agent(s) or structural class of PCBs responsible for these effects have not been delineated. In contrast, based on a toxic equivalency factor approach, the reproductive and developmental problems in certain wildlife populations appear to be related to the TCDD-like PCB congeners. 153 refs., 2 figs., 1 tab.
- OSTI ID:
- 6755644
- Journal Information:
- Environmental Health Perspectives; (United States), Vol. 100; ISSN 0091-6765
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
POLYCHLORINATED BIPHENYLS
CARCINOGENESIS
STRUCTURE-ACTIVITY RELATIONSHIPS
ENZYME INDUCTION
ISOMERS
METABOLIC ACTIVATION
METABOLITES
MIXED-FUNCTION OXIDASES
OCCUPATIONAL EXPOSURE
PRENATAL EXPOSURE
AROMATICS
CHLORINATED AROMATIC HYDROCARBONS
ENZYMES
GENE REGULATION
HALOGENATED AROMATIC HYDROCARBONS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDOREDUCTASES
OXYGENASES
PATHOGENESIS
PROTEINS
560300* - Chemicals Metabolism & Toxicology