Dichlorodiphenyldichloroethene (DDE) in human milk from South African women

Full expressions of breast milk were obtained from 184 healthy women in Johannesburg, South Africa. The mean collection day was 51 days after parturition. Human milk samples were analyzed for p,p'-DDE concentration by gas chromatography and human milk lipids were Isolated by solvent extraction and determined gravlmetrlcally. Mean concentrations of p,p'-DDE In human milk (mg/kg fat) of Black, Colored, White, and Indian donors were: 0.99 + 0.12; 1.00 jf 0.16; 1.30 0.17; 0.76 + 0.45, respectively. The Codex Allmentarlus Commission maximum residue limit for total DDT was exceeded by 28% of the samples based only on concentration of DDE. Positive correlations were observed between DDE concentration and age class, among the Colored donors only, Including prlmlparae. No correlation was found between parity and DDE concentration, however, significant decreasing differences of DDE concentration and parity classes were found among Black donors while the opposite was found In Colored donors. The total accumulated time of previous lactations was Inversely correlated to DDE concentration. Thirty percent higher concentrations of DDE were observed In those smoking between 11-20 cigarettes per day than those smoking less than 10 cigarettes per day. Levels of DDE in human milk (mg/kg fat) are comparable to other Western countries and those in the Global Environmental Monitoring System. 53 Introduction Ever since the discovery of DDT In human milk by Laug and co­ workers In 1951, Interest In the presence and levels of environmental contaminants In human milk has continued. Jensen (1983) extensively reviewed the extent of human milk contamination. While organochlorlne pesticides are banned In Industrialized countries, they continue to be used in many developing countries because. In general, they are effective and persistent, but less expensive and less toxic to the non-target organisms than the organophosphate Insecticides. The Republic of South Africa plays an Important role In world economy, especially in relation to its natural resources. However, agriculture is also an important Industry. South African agriculture is at an intermediate stage of development (Van Dyk et al., 1982). It is not as intensive and highly mechanized as in Industrial countries of North America and Europe, but it is also far from a subsistence agriculture as practiced in other parts of Africa. A limited amount of work has been undertaken in South Africa to evaluate pesticide residue levels in adipose tissue of various segments of the diverse population (Wlese, 1976; Van Dyk et al., 1982; Van Dyk et al., 1987), while the usage pattern of organochlorlne pesticides has changed greatly. The results of a survey undertaken in 1985 to evaluate factors contributing to and levels of 1,1'-(2,2-dichloroethenylidene)-bis 4chlorobenzene (p,p'DDE) in human milk fat of South African women in the Johannesburg area are reported in this paper. 54 Collection of milk samples and Interviews Samples of human milk were collected with an electric breast pump from 184 Individuals In Johannesburg between July and November, 1985. All women had delivered full term healthy singleton Infants and were solely breast-feeding their Infant at the time of the study. Women were enrolled In the study during their post-partum check-up. The entire contents of one breast were expressed with the Egnell mechanical breast pump (Egnell Inc., Gary, Illinois). Most samples were collected during the mother's post partum check-up at a hospital. Some samples were collected In Individual homes. Samples collected at a hospital were kept on Ice transferred to pestlclde-free glass jars, and stored at -20*C within 4 hours. Samples collected In the Individual homes were transferred to the hospital on Ice and transferred to pestlclde-free glass jars and stored at -20*C within 4 hours. The frozen samples were then transferred to a laboratory, placed In styrofoam shipping containers, and stored at -90*C until December 1985. The frozen samples were shipped air freight to Des Moines, Iowa, and transported to the Iowa State University Veterinary Diagnostic Laboratory where they were stored at -35*C for up to or all 18 mo. At the time allquots were, samples were thawed overnight In a refrigerator then sonicated until homogeneous by using a sonlcator water bath containing cold water. A 10 g milk sample for pesticide analysis was weighed into a 20 ml vial and sealed with a teflon lined screw cap. All allquots were immediately refrozen at -35*C. At the time of preparation for pesticide residue analysis, the samples were 55 thawed In tepid water. Donors were interviewed at the time of milk collection to obtain demographic information as well as information pertaining to parity, lactation history, use of medications, food consumption, pesticide usage, smoking habits and alcohol consumption, and assessment of any weight loss. The University of the Witwatersrand Committee for Research on Human Subjects reviewed this project and concluded that the rights and welfare of the human subjects were adequately protected, those risks were outweighed by the potential benefits and expected value of the knowledge sought, that confidentiality of data was assured and that informed consent was obtained by appropriate procedures. Methods of analysis of the milk samples Analyses were performed at the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa. Deionized water was passed through a Mllllpore Q system; each gallon of milllpore water was shaken with 250 ml petroleum ether after which the petroleum ether was discarded. Solvents were glass distilled and each 4-liter bottle was tested by gas chromatography after concentration from 250 ml to 0.5 ml. Anhydrous, granular sodium sulfate (Malllnkrodt 8024, Paris, KY) was treated at 500"C 12 hours and then maintained at 125*C. Florisil® (PR grade, 60100 mesh, Pittsburgh, PA) was activated and stored at room temperature. Elutlon patterns of standards were determined with each new lot of Florisil and for every 2 weeks. All glassware was tested for impurities.