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Revision as of 11:01, 5 October 2009
Definition of PCB:
Polychrorinated biphenyls (PCBs) is a large group of toxic synthetic lipid-soluble chlorinated hydrocarbons, which are used in various industrial processes and which have become persistent and ubiquitous environmental contaminants which can be concentrated in food chains[1].
This is the common definition for PCB, other definitions can be discussed in the article
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Notes
| PCB |
|---|
|
| Formula |
| C12H10-XClX |
| On each number may by a chlorine atom present.
This gives 209 different combinations |
Between the time of initial (1929) and final production (1977) the USA produced an estimated 0,54 billion kg of PCBs. They were widely used in transformers and capacitors, lubricants, fire retardants, plastics and other materials. PCBs can enter the marine environment by adsorption to particles and atmospheric transport[2].
They have been contaminants in the marine environment for more than 60 years. In this time they have become universally distributed in marine and estuarine environments. They occur in nearly all marine algae and animal species. Like other organochlorine compounds they are a hazard to marine ecosystems because of their extreme stability, low biodegradability and lipid solubility, which causes them to bioaccumulate. Concentrations of PCBs in surface waters vary between 0,035 n/l (in open ocean), to 10 ng/l in highly polluted coastal waters. However, decreasing trends are being observed since concentrations peaked in the 1970s[3].
PCBs tend to act as endocrine disrupting compounds, which disrupt the hormone balance of animals. This might cause immunodeficiency and or reproductive problems (which have been demonstrated in marine mammals). These effects are suspected to occur at much lower concentrations than those which cause acute toxicity[4]. PCBs have been shown to cause chronic diseases in humans (such as skin lesions, reproductive disorders and liver damage) and are suspected to be carcinogenic. Concentrations which (in laboratory conditions) cause lethal effects in fish range from 10 to 300ppm (parts per million in the animal tissue). The concentrations measured during the 1970s in wild fishes and seals varied between 0,03 and 212 ppm[3].
There are 209 different forms of PCBs. Therefore, to asses the risk of PCB exposure, the sum of all these forms needs to be taken into account[3].
Case studies
Effects of xenoestogens in eelsPCB and heavy metals in beached sperm whales
PCBs and organochlorine pesticides in Antarctic algae
PCBs and organochlorine pesticides in shrimp from the Belgian North Sea
Pesticides in harbour porpoises
The relation between pollutants and disease in guillemots
Environmental standards and legislation
Included in the OSPAR list of substances of priority action
See also
OSPAR background document on PCB
References
- ↑ Lawrence E (ed.), 2000. Henderson’s Dictionary of Biological Terms. 12th edition. Prentice Hall, Pearson Education Limited. Harlow, Great Britain.
- ↑ Clark, R,B., 1999. Marine pollution. Oxford University press, Fourth edition, pp 161
- ↑ 3.0 3.1 3.2 Kennish, M. J. (1996): Practical Handbook of Estuarine and Marine Pollution, CRC Press 524 pp
- ↑ OSPAR Commission 2000. Quality Status Report 2000, OSPAR Commission, London
Please note that others may also have edited the contents of this article.
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