Levels of organochlorine pesticide residues in breastmilk and cow milk in central division of Machakos district
The levels of organochlorine pesticide residues were determined by gas chromatography in 147· human milk and 21 pooled cow milk samples, collected from two different agroecological zones of central division of Machakos, Kenya. The human milk samples were from mothers who had lived in the study area for over 5 years, were healthy and at the time breast feeding first or second child. The milk samples were collected at 1 week to 4 months postpartum. A total of 23 pesticide residues were detected in breastmilk, while 17 pesticide residues were detected in cow milk. The main organochlorine contaminants in human milk and cow milk were the DDT group, heptachlor/heptachlor epoxide and the HCH group at frequericies of 97%, 66%, 23% in breastmilk and 100%, 71%, 46% in cow milk, respectively. There was a higher prevalence of the pesticide residues in the high potential production zone as compared to the low potential production zone. Significantly (p<0.05) higher levels of ~-HCH and t-HCH in breastmilk and p,p'- DDD in cow milk were found in the low than in the high potential production zone. In breastmilk, significantly higher levels of sum DDT and aendosulfan were found in cases where pesticides were used in households as compared to cases where no use was reported. Levels of oxychlordane and a- endosulfan were lower in areas where pesticides were reportedly used on crops in the farms as compared to areas where no use was reported. Finally, lower levels of a-endosulfan were found in cases where cash crops were grown compared to areas where subsistence crops were grown while incidences were higher in the high potential production zone. The mean levels of endrin and chlordane in human milk and chlordane in cow milk were above the prescribed codex alimentarius maximum residue limit (MRL) for milk and milk products. The calculated daily intake by suckling infants in the study area of heptachlor epoxide, endrin, oxychlordane, endosulfan, chlordane and lindane from human milk exceeded the WHO/FAa acceptable daily intakes (ADI) by 70, 40, 9, 6.3, 4 and 1.6 times respectively. For cow milk on the other hand, calculated daily intakes by infants of heptachlor epoxide, oxychlordane, chlordane and endosulfan exceeded the ADI values by 30, 6, 5 and 1.5 respectively. In summary, organochlorines had been used in the study area to the extend that consumption of human and cow milk by infants exposed them to risky levels of especially heptachlor epoxide, endrin, oxychlordane, endosulfan, chlordane, and lindane. Monitoring programmes should be initiated to ensure that all avenues of exposure are documented and ways of reducing the environmental contamination by pesticide residues are developed and implemented.