Contamination Issues in Asian Developing Countries

Abstract

This chapter focuses on the contamination, bioaccumulation, and toxicological effects of dioxins and related compounds (DRCs), such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs), in Asian developing countries, with a particular emphasis on open dumping sites of municipal waste. A comprehensive investigation of soils has suggested clearly that dumping sites (DS) are potential sources of DRCs, whereas the concentrations of DRCs in soils from urban and agricultural areas in Asian developing countries were comparable to or lower than those in general background soils from developed nations. In India, notably higher concentrations of DRCs were detected in human milk from women residing around DS, compared with those from reference sites (RS) and other Asian developing countries, indicating that the residents around DS ingest greater amounts of DRCs, possibly via the intake of contaminated bovine milk and fish. Elevated concentrations of DRCs were also detected in wild animals inhabiting the Indian DS area, such as crow and pig, and the accumulated DRC profiles suggested direct transfer of these contaminants from contaminated soil. Toxic equivalents (TEQs) of DRCs and the liver to adipose concentration ratios of PCDD/Fs in pigs had statistically significant positive correlations with the levels of hepatic cytochrome P450 (CYP) 1A-like protein, suggesting the induction of CYP1A by DRCs and CYP1A-dependent hepatic sequestration of PCDD/Fs. In addition, decreases in plasma-free thyroxine and immunoglobulin G were observed in pigs from the DS. Thus, DS in developing countries are one of the main challenges for further research due to the long-term effects on environmental quality and human/animal health. The continuous formation of DRCs in DS and their elevated residues detected in breast milk from residents living around such DS warrant effect studies of these contaminants on their offspring. Comprehensive and long-term monitoring programs are urgently needed with proper capacity building in Asian developing countries, to mitigate DRC emission and their risk on ecosystems and human health.