Human health effects PCDDs

For most of the PCDDs no information on human health effects is available except that during the production of pentachlorophenol workers have developed a skin disease, chloracne (13) and complaints such as neuralgic pain in the lower extremities, and symptoms such as persistent bronchitis, and eye irritation (14). The bronchitis seems to be more prevalent in workers exposed to technical pentachlorophenol than in those exposed to the other chlorinated phenols. 

Humans with a history of exposure to 2,3,7,8-TCDD have been studied most often. Therefore, I will devote most of the rest of this paper to a review of these studies. Although exposure to other PCDDs may be as prevalent or more prevalent in the general population, we have no information on the human health effects of the other PCDDs. 

The evaluation of risk has underlined the possible adverse effects both on human health after the exposure to drinking water contaminated by landfill leachate and on small rodents and aquatic species at the hypothesized condition for humans, the estimated toxic effects of the raw leachate are mainly due to the levels of ammonia and cadmium and carcinogenic effects are induced by arsenic first and then by PCBs and PCDD/Fs while ecological potential risk is mainly attributable to the concentration of inorganic compounds, in particular ammonia for small rodents, cadmium, ammonia, and heavy metals for fishes. 

The Stockholm Convention on POPs lists 22 priority chemical substances that pose potential risks of causing adverse effects to human health and the environment. Since the convention was enacted in 2004, evidence for the toxic effects of POPs such as DDT, dichlorodiphenyldichloroethylene (DDE), PCBs, PCDD/Fs and other halogenated compounds has been demonstrated for both humans and wildlife. 

Although the effects of chronic exposure of humans to low levels of POPs are difficult to predict, some biological effects have been described. For example, exposure of children to PCBs and PCDD/Fs may be linked to an elevated risk for infectious diseases. Exposure of pregnant women to PCDD/Fs may cause lower fertility in their male offspring. The adverse effects to human health of acute and chronic exposure of high concentrations of POPs, especially among industrial workers exposed to daily intakes of chemicals, are more evident. Elevated concentrations of DDE and TCDD have been associated with the development of cancers such as breast cancer, leukaemia and thyroid cancer. Dioxin exposure may also be associated with immunotoxicity, reproductive diseases and neurotoxicity. Extreme exposure to chlorinated compounds has resulted in death [101]. 

The Stockholm Convention is a global treaty committing the international community to protecting human health and the environment from the potentially harmful effects of POPs (UNEP Chemicals, 2005). The United Nations Environment Programme (UNEP) has identified 12 most toxic POPs (the Dirty Dozen ) for control under the Convention, including 10 intentionally produced POPs pesticides/industrial chemicals (aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex, toxaphene and polychlorinated biphenyls (PCBs)) and two unintentionally produced POPs by-products (polychlorinated dibenzo-/ -dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)). In implementing the Convention, Parties to the Convention will take measures to restrict the trade, production and use of the intentional POPs and to reduce and, where possible, to ultimately eliminate the production and release of the unintentional POPs by-products. 

A. Specific levels. It is difficult and expensive to detect dioxins in human blood or tissue, and there is no established correlation with symptoms. There are many congeners of PCDDs, PCDFs, and PCBs the individual contribution of each to toxicity is unclear. Unexposed persons have a mean of 7 pg of 2,3,7,8-TCDD per g of semm lipid, compared with workers producing trichlorophenols, who had a mean of 220 pg/g. The highest recorded level is 144,000 pg/g blood fat in a patient with few adverse health effects other than chloracne. 

The severe health effects observed in the Japanese Yusho incident of 1968 were attributed to the ingestion of polychlorinated biphenyls (PCBs). At that time, the forefront of analytical chemistry was represented by the determination of trace components at the parts per million (ppm) concentration level. It was not until about ten years later that analytical methodology was able to detect polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs) at concentrations of 10 parts per billion (ppb) or less in the presence of PCBs. The significance of the determinations lies in the assessment of risk to human populations exposed to undegraded PCBs and to mixtures of chemically similar compounds of concern derived from uncontrolled reactions such as might occur when a PCB filled transformer undergoes eventful failure. 

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