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Monday, May 2, 2011

POLYCHLORINATED BIPHENYLS

Poly chlorinated biphenyls are (PCBs) are liquid, first manufactured in the 1930s, Which have become widely distributed in the environment; particularly in water, fish and fish-eating birds; and in soils near sources of contamination.
PCBs have been used for their electrical insulating properties in transformers, capacitors ( even in some domestic equipments), heat transfer and cooling systems, hydraulic systems and vaccum pumps, and a variety of other uses. Use of PCBs has now been restricted or stopped in numerous countries, but certain occupational groups are still exposed, notably in handling of chemical wastes, dealing with fires or accidents, working in or cleaning contaminated areas of servicing and dismantling old electrical apparatus; and the public in the vicinity of incinerators if the temperature is not high enough. Low levels of PCBs can be detected in many members of most industrial populations, and are concentrated in human milk. Poisoning by PCBs has been recognised as a result of occupational exposure, and in outbreaks in the general population, such as occurred in japan (Yusho disease), and in Taiwan, due to contamination of rice oil.
Clinical features
The most striking effects are hyper secretion of tears, pigmentation and acne form eruptions of the skin and persistent productive cough. Headaches and other non-specific central nervous system disturbances occur, and paraesthesias; also liver damage and immunosuppression, Some deaths have occurred, mostly from liver disease, including hepatomas. Babies of exposed mothers are small and pigmented, and fetal deaths and abnormalities were common in the Yusho outbreak. Acute exposure irritates the eyes, skin and respiratory tract.
Management
Treatment consists of withdrawal from exposure, and general supportive measures. No specific treatment is available.

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