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Polychlorinated biphenyls (PCBs) are among the most dangerous persistent organic pollutants. PCBs were produced by multinational chemical companies such as Monsanto, Bayer, Rhone Poulenc and Mitsubishi. They were widely marketed and used in oils and additives in a lot of applications worldwide. Persistent against all environmental factors such as fire, sunlight and biological degradation the chemical became extremely popular, but left us with an environmental nightmare.
The period of the main production was 1940-1980, although, by 1965, the first evidence of contamination and biomagnification was found in sea mammals of the Baltic Sea. Other reports followed, and after incidents with poisoning of humans in Taiwan and Japan, a ban was put in force in most countries about 1980. The following years have been a race against time trying to identify and destroy the PCB-containing products before they adversely affect the environment. Some governments and environmentalists have done this work, with the producers denying their responsibility.
Even if production of the PCB oils and additives was banned in the early 80s, the total load to be borne by the environment is likely to increase in the years to come. This is because the main use of PCBs was in products with a long technical lifetime, such as building materials, paints and electrical equipment, not discreet industrial, outlets but diffuse and long term sources of pollution . Every installation normally contains hundreds of kilograms of PCB.
PCBs that have already leaked out into the environment have spread to every corner of the earth and accumulated in the food web. Levels in harbours and coastal waters, close to the sources, are horrifying, and even in ‘pristine’ oceans, sea mammals have accumulated toxic levels. . PCBs in aquatic environments adhere to small particles which are readily absorbed by plankton and filtering-feeding or mud-dwelling organisms. Complex marine food chains allow the chemical to concentrate in dangerous amounts in the higher trophic levels (biomagnification). This is due to PCBs being readily soluble in hydrophobic media, such as oily or fatty substances, which means they can be easily incorporated in any lipid deposits in any organism and hardly destroyed or excreted. PCBs enter the body mainly by ingestion, but also directly through skin and lungs. (Knutzen et al. 1999)
High- risk groups include whales, dolphins, seals, seabirds, polar bears and also seafood dependant human populations. Many of the marine mammals and sea birds worldwide have such high PCB-levels in their bodies that they themselves exceed the limits for toxic and hazardous waste (Cummins 1998). PCB-levels in seafood and human blood have been detected in many countries (For example most of Scandinavia and Europe) exceeding the World Health Organisation (WHO)-given safe limits.(Schulze 1999) The result can be reproductive, immune and behavioural disturbances in those animals and humans exposed and their offspring. In Sweden, birthweight has been found to be reduced and the perinatal mortality rate is higher than expected in regions with high consumption of fatty fish from the Baltic Sea. As a result of this, women have been advised to stay away from this traditional seafood. From studies around Lake Michigan, it has been shown that children who have been exposed to PCBs whilst in the womb, have retarded cognitive development. (Jacobson and Jacobson, 1996, Darneryd et al. 1995) The same effects are found in children of people exposed to the two famous PCB-accidents in Taiwan and Japan.
Among other symptoms recorded in mammals, Swedish research on seals in the Baltic sea has revealed immune system damage, infertility, tumours and skeleton and skin deformities (Bergman 1999). Recent research on polar bears (by Norwegian Polar Research Institute), has for the first time showed direct links between PCB-levels and defects in the immune system and reproduction. And there is worse to come! Most of our ecosystems have not yet been investigated for effects. For example, there are great concerns about the fate and effects of PCBs in deep-sea habitats. There is also some evidence that the documented decline of PCB-levels in some hot-spots and local animal populations is due to more dispersed distribution than before throughout the global ecosystem rather than a real breakdown of the toxin. The “half-life” of the chemical in sediments and soil is expected to be tens, maybe hundreds of years.(Knutzen et al. 1999)
Within such long timeframes there will be repeated incidents involving release of PCBs from these sinks, affecting biota, even if the direct outlets are stopped immediately.
References:
Bergman Anders.(1999) ’Health condition of the Baltic grey seal (Halichoerus grypus) during two decades. Gynaecological health improvement but increased prevalence of colonic ulcers.’ APMIS. 107(3). March, 1999. 270-282.
Darneryd P.O. et al. (1995). PCBs and dioxins in fish, article with compilation of background material. Vaar Foeda. No 2. 1995. Svenska Livsmedelsverket ( Swedish Government for Food health and Safety).
Cummins J.E. (1998), ‘PCBs, can the sea mammals survive them’. The Ecologist. Vol.28.No. 5. 1998
Jacobson J.L. and Jacobson S.W. 1996. Intellectual impairment in children exposed to polychlorinated biphenyls in utero. New England Journal of Medicine 335: 783-789
Knutzen, (a.) (1999) Rapporten “Micropollutants in Norwegian Fauna – including Arctic and Antarctic", Report nr5 1999 made by several research institutions in cooperation. Compilation of current knowledge. Direktoratet for naturforvaltning (Norwegian government for Nature management). Trondheim
Schulze P-E and Wiborg M. 1999. PCB sources along the Norwegian coast Kristiansund – Oslo- Fredrikstad. Report from The Great Toxic Hunt 1998. Friends of the Earth Norway, Oslo
