Pesticide application and increased dioxin body burden in male and female agricultural workers in China

Large amounts of the powerful pesticide sodium pentachlorophenol (Na-PCP) salt have been sprayed over vast areas in central China to control schistosomiasis, a parasitic disease of epidemic proportions. Approximately 6000 tons of Na-PCP are produced in China annually. Dioxins, a class of toxic, persistent compounds, are found as impurities in commercial Na-PCP products. These contaminants are released into the environment and significantly contribute to human exposure to dioxins in China. This study was carried out to determine dioxin levels in environmental and human tissue samples from one schistosomiasis area to evaluate the health risks associated with exposure to Na-PCP. Na-PCP pesticide was applied in 1972, 1973, and again in 1978. A total of approximately 454 tons and 902 tons of 5-ppm Na-PCP in water were sprayed over large land and lake problem schistosomiasis areas, respectively. The groups studied were (1) sprayers or handlers of Na-PCP, (2) persons living in the sprayed areas, and (3) persons living in unsprayed areas 300 km north of the sprayed lake located in a city in the Jiangxi province. Individual whole-blood and breast-milk samples were collected and later pooled for dioxin analysis. Also, a sample of commercial Na-PCP was collected. In addition, sediment samples from the lake where Na-PCP was sprayed were collected from four different sites and one control sample was collected from a non-schistosomiasis area. All of the samples were analyzed by high-resolution gas chromatography/mass spectrometry. A sample of Na-PCP used in schistosomiasis regions was analyzed and levels of 2,3,7,8-substituted dibenzodioxin (PCDD) and dibenzofuran (PCDF) congeners were measured. In addition, the international dioxin toxic equivalent (I-TEQ) value of this sample was calculated. Total I-TEQ of 162 parts per billion (ppb) was found in the Chinese Na-PCP product. A pooled breast-milk sample from mothers, female agricultural workers who were born in the schistosomiasis areas where large amounts of Na-PCP were sprayed, had an I-TEQ of 5,4 parts per trillion (ppt), lipid, which was about double that of mothers from control regions, women born in areas not sprayed with Na-PCP (2.6 ppt, lipid). The dioxin I-TEQ values in human blood ranged from 9.0 (subjects 15 to 19 years of age) to 16.3 ppt, lipid (subjects 35 to 70 years of age) in the whole-blood samples from Na-PCP exposed persons, whereas the general population's whole-blood I-TEQs were 4.8 and 6.4 ppt, lipid, respectively. The PCDD/F congener distribution patterns in four sediment samples from schistosomiasis areas were similar to that of Na-PCP. By comparison of specific "fingerprint" congeners (higher chlorinated dioxins and the closely related dibenzofurans) in Na-PCP, human tissues, and sediment samples, we conclude that the chemical pesticide Na-PCP is a source of environmental and human dioxin exposure in the Chinese schistosomiasis area studied. Although human PCDD/F tissue levels in China are low compared with those in more industrialized countries, the elevated I-TEQ levels in exposed persons are cause for concern.