Polychlorinated dibenzo-p-dioxins and dibenzofurans in lake sediments from Chinese schistosomiasis areas.

Lake D is located in the south of China. The total area of the lake is about 3,000 km. The dimension of the lakeland varies greatly with changing of seasons. It is an important source of grain and freshwater fish in China. However schistosomiasis japonica prevailed in this region for a long time, sodium pentachlorophenate(Na-PCP) has been sprayed since the 1960s to control the spreading of snailborne schistosomiasis. Being contaminants of technical Na-PCP, PCDD/Fs may enter the environment and contribute to human exposure after the treatment. The low water solubilities and high adsorption to sediment of PCDD/Fs do not rule out their movement in the environment. Schecter et al. (1994) compared PCDD/Fs levels in blood and milk in agricultural workers and others following Na-PCP exposure in another schistosomiasis area in China, high levels of PCDD/Fs in exposed persons are evident. But the investigation concerning the contamination of Lake D has not been carried out before this study.