In Situ Technologies for Reclamation of PCB-Contaminated Sediments: Current Challenges and Research Thrust Areas

Polychlorinated biphenyls PCBs were manufactured for use mainly as insulators, coolants, and dielectric fluids in electrical equipment owing to their inert, stable, and flame-retardant nature. They were banned in 1979 because of their toxicity and persistence in the environment. Between 1929 and 1977, approximately 1.25 billion pounds of PCBs were manufactured in the United States. Because of past disposal practices and accidental releases that continue to the present day, 450 million pounds of PCBs have entered the environment over time ATSDR 2000 . Moreover, their hydrophobic nature has led to their occurrence predominantly in soils and sediments that act as sources for their long-term release to the environment. PCBs bioaccumulate and biomagnify in the ecosystem, starting from submarine sediments and benthic organisms to seaweeds and fish, progressively moving up the food chain to reach humans, posing serious health hazards. The Yusho PCB poisoning incident occurred in 1968 in Japan and involved more than 1,860 individuals, who consumed rice bran oil contaminated with PCBs and its oxidation products. The victims suffered from chloracne, hyperpigmentation, dermal lesions, and ocular discharges—symptoms that slowly lapsed over many years. However, other symptoms relating to the enzymatic or endocrinal effects persisted after more than 30 years Masuda 2001 , with several patients complaining of chronic bronchitis, peripheral numbness, fatigue, and headaches decades after the incident Aoki 2001 . A similar exposure to PCB-contaminated oil led to the Yu-Cheng episode in Taiwan in 1979, resulting in more than 2,000 victims with related symptoms. Additionally, children with prenatal and lactational exposure showed lower birth weights and impaired intellectual and cognitive development Aoki 2001 . More recently, the Belgian PCB incident occurred in 1999, when 2,500 farms were inadvertently supplied with animal feeds contaminated with a mixture of PCBs and dioxins Bernard et al. 2002 . Poultry was hardest hit: egg production and hatching decreased, and a chicken edema epidemic broke out van Larebeke et al. 2001 . As an aftermath of the contamination, poultry and derived products were ordered off the markets, and some 2 million chickens were destroyed van Larebeke et al. 2001 . Even though this episode did not cause or is unlikely to cause adverse