Organochlorine pesticides in Kenyan mothers'- milk: levels and sources
Kanja, L W
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Human milk samples were collected from eight areas in Kenya with different agricultural activities. All the mothers had lived within the area for the last five years. They were healthy and breast feeding their first or second child. In 264 mothers milk samples analysed, 13 organochlorine pesticide residues were detected in the following order of frequency: p,p'-DDT (100%), p,p'-DDE (100%), BCB (60%), aldrin (35%), lindane (30%), P-HCH (27%), dieldrin (20%), o(.,-HCH(8%), transnonaclllor (6%), heptachlor (4%), endrin (4%), heptachlorepoxide (0.4%), and oxychlordane (0.4%). No residues of PCBs were found. Great regional differences in the levels of these compounds were found; and the mean levels of sum DDT ranged from 1.69 mg/kg in milk fat of nomads from Loitokitok to 18.73 mg/kg milk fat in human milk from Rusinga Island. Regional differences were also found in the mean ratio of p,p'-DDT to its more persistent metabolite p,p'-DDE, with mean levels ranging from 0.7 in Karatina to 4.4 in Turkana. Similarly, the results demonstrated significant differences (P<0.05) in the mean levels of sum DDT and the ratio of p,p'-DDT to p,p'-DDE within the various sampling area depending on the agricultural activities. The results demonstrate large contamination of Kenyan human milk with organochlorine pesticides, especially DDT and DDE. The levels of sum DDT obtained were higher than corresponding levels reported from industrialized countries, and the estimated daily intake of a Kenyan infant exceeded the Acceptable Daily Intake set by the WHO/FAO. There was also a positive correlation of sum DDT, and P,P'-DDT to P,P'-DDE ratio with the mother's age. The results were also examined in relation to differences in living conditions with regard to agricultural activities, dietary habits, and reported use of pesticides in the various sampling areas. Examination of commercial infant milk formulas on the Kenyan market revealed that only one contained organochlorine pesticides, and the levels were low, being 0.05 mg DDE/kg milk fat and 0.06 mg dieldrin/kg milk fat. The time trend (1983-84) in DDT contamination in Turkana where DDT was extensively used in cotton growing, was also investigated. The changing from growing cotton to food crops within 9 months was followed by a reduction in the mean level of sum DDT f roru 7.79 to 4.49 mg/kg milk fat. Human food samples were examined for organochlorine pesticides in order to determine the sources of these compounds in the human body. Of the 243 food samples examined, about 50% of them contained at least one organochlorine residue, but generally the levels were low. The DDT-group was most commonly found in fish, cow's milk, vegetables and cereals. Lindane had a high incidence of occurrence in all the food s~mples examined. Other organochlorines detected were aldrin, a!-HCH, P-HCH transnonachlor, oxychlordane, dieldrin. PCBs were not detected. The mean sum DDT found in fish was 128 ug/kg and p,p'-DDE was the major metabolite. The dietary intake of the different organochlorines through food samples varied in the different areas. The occurrence of pesticide residues in food appeared to be closely associated with the use of similar pesticides in the area. Foods of animal origin contained higher levels of the DDT group as compared to other food groups in all areas. In general, a mothers daily intake of sum DDT was lower than the infants daily intake of sum DDT through breastfeeding, which demonstrates mobilization and excretion of stored pesticides in the mothers milk. Samples of maternal blood, milk, subcutaneous fat, as well as umbilical cord blood were collected from mothers and their infants at Kenyatta National Hospital. The mothers were healthy but delivered by Cuesarean operation. In the 41 samples analysed, the DDT-group occurred in all, dieldrin ill 11, transnonachlor in 6, J-HCH in 5, endrin in 2 and lindane in 1. The mean levels (mg/kg fat) of sum DDT were 5.91 in subcutaneous fat, 4.86 in mothers milk, 2.75 in maternal serum and 1.87 in umbilical cord serum. J -HeH was only found in subcutaneous fat and milk with mean levels of 0.034 and 0.26 mg/kg fat, respectively. Dieldrin, endrin, and transnonachlor were detected in maternal ser~m but not in umbilical cord serum. Dieldrin detected in mothers milk and subcutaneous fat could not be quantified. There was a significant correlation between the levels of sum DDT in subcutaneous fat and milk fat (r=0.963), subcutaneous fat and maternal serum fat (r=O.843), and maternal serum fat and maternal milk fat (r=0.868), indicating the coherellce of DDT in the body and demonstrates that human milk is a suitable indicator of monitoring organochlorine contaminants in the human body.