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.