Polychlorinated biphenyls (PCBs): Characteristics, toxicity, phytoremediation, and use of transgenic plants for PCBs degradation

Polychlorinated biphenyls (PCBs) are a class of chlorinated aromatic organic compounds listed as persistent organic pollutants because of their thermal and chemical stability. The high toxicity and bioaccumulation of these xenobiotics in the food chain impose a hazardous threat to our biotic system and ecosystem. Higher consumption of foods cultivated in PCB-enriched environment can result in neurotoxicity, carcinogenesis, developmental and reproductive toxicity, dermal toxicity, endocrine effects, hepatotoxicity, and the induction of diverse phase I and phase II drug-metabolizing enzymes. Increasing public awareness and concern has impelled researchers to identify ways to remove these hazardous organic compounds from the environment. Efforts have been made to devise strategies to avoid entry of PCBs in food chain. Among the various available strategies, microbial assisted PCB degradation is found to be very effective and has thus been widely considered. Many microorganisms with the capability of degradation of PCBs have been reported, for example, Pseudomonas aeruginosa, Burkholderia xenovorans, Arthrobacter sp. strain B1B, Ralstonia eutropha H850, and Rhodococcus sp. strain RHA1. Plant genetic transformation technology has facilitated scientists to develop cultivars with novel traits and enhanced resistance against abiotic and biotic stresses. Bacterial genes (e.g., biphenyl dioxygenases) can be expressed in target plant species for effective treatment of PCBs. This chapter will describe chemistry, sources, transport, and toxicity of PCBs. Recent developments in phytoremediation strategies for the removal of PCBs by using transgenic approaches will also be discussed.