Date: 11 Nov 2002

Background Contamination of Humans with Dioxins, Dioxin-Like PCBs and Other POPs

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Abstract

Since the first finding of the insecticide DDT in human tissues, the problem of persistent organic pollutants (POPs) has become a growing issue of special public and toxicological concern. In the past few decades numerous reports have assessed the global distribution of contaminants, such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polybrominated flame retardants. Consumption of food has been shown to be the major pathway of human background exposure to POPs. Because humans are at the top of the food chain, it is obvious that human tissues may contain relatively high concentrations of those lipophilic residues and contaminants that tend to bioaccumulate in the food web. Human body burden can best be determined by analysis of human adipose tissue, blood or breast milk. For a meaningful risk assessment, it is important to precisely characterise the specimens, because it was demonstrated that factors such as age, consumption habits, changes in body weight or nursing status might have a severe influence on human body burden.

Analyses of human tissue samples from industrialized countries for organochlorine pesticides show a significant decrease within the past 20 years. This demonstrates that the ban of these pesticides in the Western World in the early 1970s had a beneficial effect on human body burden. On the other hand, human samples from countries with an ongoing application of persistent insecticides for vector control, such as DDT, may still contain elevated pesticide levels. A decrease can also be seen for polychlorinated biphenyls in human samples from those countries which early banned the use of technical PCB mixtures in open systems and strictly regulated their use in closed systems as well as their disposal.

In general, human samples from industrialized countries show higher PCDD/PCDF levels than corresponding specimens from developing regions. An exception represents, however, certain Inuit cohorts living in Greenland and Northern Quebec who show the highest “background” contaminant values world-wide. Because of numerous measures which were taken to reduce PCDD/PCDF emissions into the environment, a significant decline of these compounds in humans living in industrialised countries was observed between the late 1980s and the middle of the 1990s. Since then, however, this declining trend seems to have come to a stop.

Results on dioxin-like PCBs in former and present human specimens are still scarce. Those data available indicate, however, that these compounds may contribute significantly to human body burden, expressed as total TEQ values.

In contrast to most other persistent organic pollutants, polybrominated diphenyl ethers (PBDE) widely used as flame retardants do not show a comparable decreasing trend in human samples. Recent analyses rather demonstrate an ongoing human exposure to these contaminants.