Biphenyls: Health Impacts and Toxicity Evaluation

Biphenyl is an aromatic hydrocarbon, occuring naturally in crude oil, coal tar and natural gas or produced synthetically as a by-product during benzene production. Synthetically manufactured polychlorinated (PCBs) and polybrominated (PBBs) biphenyls have serious health impacts on human beings. Therefore, biphenyls are banned in many countries including US, UK, India, Japan, etc., but are still present in the environment. This chapter is a comprehensive discussion on biphenyls based on available literature. It includes a brief introduction about physical and chemical nature of biphenyls, their applications, health impacts and toxicity evaluation. Various entry routes of these chemicals in the environment e.g., improper disposal/ incineration of industrial wastes containing PCBs and PBBs, leakage from old electronic instruments, accidental spillage of these chemicals during transportation/ handling, etc, have also been discussed. PCBs and PBBs do not degrade readily and stay in different environmental media for longer durations and enter food chain and bioaccumulate in human bodies via dermal, inhalation and oral exposure routes. High exposure to biphenyls leads to various health problems such as neurological, reproductive, hepatic, gastrointestinal and renal disorders, endocrine disruption, cancer, etc. Various techniques used for the identification or estimation of PCBs in the environment and biological samples such as gas chromatography coupled with electron capture detection (GC-ECD) or mass spectrometry (GC-MS), high resolution gas chromatography (HRGC), etc. have been discussed briefly. Moreover, various assays employed for the assessment of toxic effects of PCBs and PBBs, using prokaryotic/ eukaryotic models and different remediation techniques for these chemicals have been discussed.

Keywords: Aromatic hydrocarbons, Biphenyls, Cancer, CARDIA, Daphnia magna, ECNI, Electronic waste, NHANES, Organic pollutants, Phytoextraction, Phytotransformation, Polychlorinated biphenyls, Polybrominated biphenyls.