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Expert panel of the World Health Organisation discusses health assessment of PCBs

26/2001, 11.09.2001

It is indeed true that the contamination of humans with polychlorinated biphenyls (PCBs) has fallen considerably in recent years in Germany. However, people are still taking in relatively high volumes of PCBs through foods and, to a lower extent, from air. Headlines about schools contaminated with PCBs have considerably worried parents, pupils and teachers in recent weeks. One thing is sure: PCBs can damage health but there are many unanswered questions. The assessment of the health effects of PCBs was also a topic at an international expert panel of the World Health Organisation (WHO) which met at the Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) in Berlin for an exchange of opinions on 3 and 4 September 2001. The focus was on so-called non-dioxin-like PCBs, polychlorinated biphenyls, which show no or little similarity in their action with that of highly toxic dioxins. The experts from eight countries agreed that the contamination of the population with PCBs must continue to be dramatically reduced.

In the past, polychlorinated biphenyls were used because of their physico-chemical properties to a large-scale for instance in adhesives, as plasticizers in paints, as sealing compounds and as cooling agents in transformers. Today, PCB-containing sealing and jointing compounds are one of the main sources of higher PCB concentrations in indoor air. Since 1989 the use of polychlorinated biphenyls has been banned in Germany. Humans mostly take in PCBs through food of animal origin and, to a lesser extent, from indoor air. PCBs accumulate in fatty tissue. The group of polychlorinated aromatic biphenyls takes in around 200 substances. Amongst other things they damage the immune system and the central nervous system. Some have effects similar to dioxins. These substances are, therefore, called dioxin-like PCBs. Other polychlorinated biphenyls show little or no similarity in terms of their effect to that of dioxins and are, therefore, called non-dioxin-like PCBs.

In 1998 WHO laid down a tolerable daily intake (TDI) which takes in both dioxins and furans as well as 12 dioxin-like PCBs. The value is 1-4 picogram (pg), i.e. one trillionth of a gram, so-called dioxin equivalents (WHO-TEQ) per kilogram (kg) body weight (bw). Along the lines of precautionary consumer protection the lower value of 1 pg WHO-TEQ/kg bw has since been taken by BgVV and UBA as the target value for health risk assessment.

Given that this evaluation concept does not include the group of non-dioxin-like PCBs, there are uncertainties in the risk assessment of this group of substances. Many PCBs are poorly degradable and accumulate in the food chain. They account for the major share of PCBs which are found in breast milk and body tissue. In animal experiments effects were observed amongst other things on the nervous system and the hormonal balance. Tumorigenic effects are also documented. The statements about the effects in humans are contradictory.

For BgVV and UBA this raises the question whether the health effects of non-dioxin-like PCBs have possibly been underestimated because of the lack of an evaluation concept for them in risk assessments or whether the dioxin-like PCBs constitute the more critical substance group and limiting their intake volume constitutes sufficient health protection for consumers for non-dioxin-like PCBs, too. This question is now to the fore of expert discussions within WHO. Prior to a definitive assessment whether separate evaluation yardsticks are necessary for this substance group, the expert group wishes to carefully examine all the available data. This first exchange of experience is to be followed by a further international expert discussion. A report about the meeting in Berlin is being prepared by WHO.

The reassessment of non-dioxin-like PCBs is also grounds for examining the current decontamination recommendations for PCB-contaminated buildings. A working group within UBA of the Federal Government and the Länder, which elaborates recommendations for handling indoor contaminants, has begun its consultations on this issue. Until the conclusion of these consultations the Federal Environmental Agency recommends undertaking decontamination measures for indoor contaminations with polychlorinated biphenyls on the basis of the so-called PCB Directive. Health and building experts from the Federal Government and Länder already agreed on action recommendations for the decontamination of PCB-contaminated buildings in the mid-1990s. Many federal Länder have taken over the PCB Directive in a binding manner into building law but it is not always consistently implemented.

According to the PCB Directive less than 300 nanogram - 1 nanogram is one billionth gram - PCB per cubic metre indoor air is viewed as tolerable in the long-term. At values of between 300 and 3,000 nanogram per cubic metre air, the source of air pollution should be identified, removed if possible whilst bearing in mind the principle of commensurateness or efforts should be made to at least reduce the PCB concentration, for instance through thorough cleaning and dedusting of the rooms. Concentrations of over 3,000 nanogram per cubic metre indoor air should be avoided. For these values control analysis should be undertaken and measures immediately taken to reduce the concentrations. The target value for decontaminations is less than 3,000 nanograms PCB per cubic metre air.


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