Breast milk contamination in Kazakhstan: implications for infant feeding.

To assist the Ministry of Health of Kazakhstan in making infant feeding recommendations, breast milk samples were analyzed for PCDDs/PCDFs, PCBs, chlorinated pesticides, toxic metals, and cesium-137. Sampling sites were selected to provide a profile of representative exposures to possible contaminants; 92 breastmilk samples from 7 sites were analyzed for chlorinated contaminants and 115 samples from 8 sites were analyzed for toxic metals and cesium-137. With three important exceptions, concentrations of chlorinated contaminants and toxic metals were similar to or lower than those in Europe. Cesium-137 was not detected in any samples. The exceptions were localized contamination with the most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and generalized contamination with beta-hexachlorocyclohexane and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDT). The localized high concentrations of TCDD (range 6.2 to 118.2 pg/g fat) are the highest documented in the world in a population currently of reproductive age. Calculated incremental lifetime excess cancer risk to an infant exposed to these high concentrations of TCDD range from 28 to 82 x 10(-5). Based in part on the results of this study, the Ministry of Health is promoting breast feeding. However, possible adverse developmental effects associated with both prenatal and postnatal (through breast milk) TCDD exposure have not been adequately assessed. Further epidemiologic research is needed to examine these effects in this newly identified high-risk population.