Organochlorine pesticide residues in breast milk of mothers living in Nairobi, Kenya

Abstract

A total of 216 human milk samples were collected from mothers either attending post natal clinics or in the maternity wards of some hospitals in Nairobi. The samples were analysed for organochlorine pesticides by use of a gas liquid chromatograph equipped with a 63Ni electron capture detector. Thirteen organochlorine pesticides were detected in the following order of frequency:- p,p'- DDE (99.5%), p,p'-DDT (78.2%), dieldrin (37.5%), I)-HeH (16.2%), lindane (16.2%), o,p'-DDT (11.5%), a-HeH (11.1 %), heptachlor (10.2%), p,p'-DDD (9.3%), aldrin (5.6%), heptachlor epoxide (4.2%), endrin (2.7%), and o,p'-DDD (0.44%). The mean level (mg/kg milk fat) of sum DDT in all the human milk samples analysed was 0.47 and ranged from 0.004 to 6.32. Mean levels (mg/kg milk fat) of the other residues identified were as follows:- dieldrin 0.022, I)-HeH 0.089, lindane 0.017, a-HeH 0.067, heptachlor 0.026, aldrin 0.03, heptachlor epoxide 0.017, and endrin 0.035 .. There were significant differences (p<0.05) in the levels of sum-DDT and p,p'- DDE, in relation to the parity of the mother with higher levels being observed in mothers nursing their first child as compared to those nursing their second child. Mean level (mg/kg milk fat) of sum-DDT was 0.51 in primipara and 0.41 in secundipara while mean level (mg/kg milk fat) of p,p'-DDE was 0.32 in primipara and 0.28 in secundipara.The other factors found to affect the levels of organochlorine pesticides in this study were, maternal age and fat content of the milk. Diet, social class and race of the mother were not significant contributors (p>0.05) to the pesticide levels in the human milk. The mean ratio of p,p'-DDT to p,p'-DDE was low implying less exposure of the population to the parent compound p,p'-DDT. The levels of the organochlorine pesticides in this study were lower than levels observed in an earlier study carried out in the rural areas of Kenya and also in some cases lower than levels observed in earlier studies carried out in some industrialised countries. The estimated daily intake of sum-DDT, dieldrin, aldrin and endrin by the infant was found to exceed the acceptable daily intake (ADI) set by the World Health Organisation. Food samples collected from major markets in Nairobi were examined for organochlorine residues. Contamination of the food samples with organochlorine pesticides was low and only residues of dieldrin, p,p'-DDE, p,p'-DDT were detected. Food of animal origin was found to contain higher levels of organochlorines than food of plant origin. Although the contamination of food with organochlorine pesticides was low the presence of DDT, DDE and dieldrin in some food stuffs demonstrated that food could be one of the sources of these compounds in the human milk.