Organochlorine pesticide residues in mothers' and cow milk in Iganga and Kampala districts, Uganda
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The extent of environmental pollution as a result of extensive and indiscriminate use of pesticides in Uganda has not heen well established. Organochlorine pesticides in particular are persistent in the environment and have the ability of translocation and biomagnification along the natural food chains. Since man is at the top of most food chains, higher levels of these chemicals accumulate in the body which could be harmful to health. Of special concern are the breast-fed infants who could be regarded as the terminal link in the human rood chain. A total of 143 samples of mothers' milk were collected from two districts in Uganda and analyzed for the presence of organochlorine pesticide residues. Sixty of the samples were collected from mothers residing in urban areas of Kampala District and 8:3 samples were collected from mothers living in rural areas of Iganga District. The samples were collected from mothers aged between 18 and 30 years and were breast-feeding their first or second child during the first week to four months post-partum. The main objective of the study was to identify, and quantify the levels of organochlorine residues in mothers' milk and subsequently examine their toxicological implications to the health of the breast-fed infants. Out of all the mothers' milk samples analyzed, eight organochlorine residues were found. T ese were: p,p'-DDE (100%), p,p' -DOT (100%), dieldrin (83.2 %), o.p' -DOT (74.8%), B-HCH (9.1 %), p,p'-ODD (3.5%), cy-HCH (3.5%) and lindane (1.4%). Their mean levels in mg/kg milk fat in all the samples were: sum-DDT 3.24, p,p' -DDE 2.35, p,p'-DDT 0.57, o,p'-DDT 0.06, p,p'-DDD 0.08, dieldrin 0.07, a-HCH 0.10, B-HCH 0.07 and lindane 0.44, Sum-Drrl was calculated as p,p'-DDT + o,p'-DDT + 1.ll(p,p'-DDE -+ p,p'-DDD), 1.11 heing a conversion factor for the lower molecular weight of the DIH metabolites. The mean percent extractahle milk fat in all the samples was 2.9%. In Kampala District, the mean levels of the residues in mg/kg milk fat were: sum-DDT 3.97, p,p-DDE 2.84, p,p' DDT 0.76, o,p'--DDT 0.07, p,p'-DDD 0.04, dieldrin 0.06, a-HCH 0.46, B-HCH 0.06 and lindane 0.87, while in Iganga District their mean levels in mg/kg milk fat were: sum-DDT 2.71, p,p'~DDE 2.00, p,p'--DDT 0.44, o,p'-DDT 0.06, p,p'-DDD 0.09, dieldrin 0.07, a-HCH 0.01, B-HCH 0.07 and lindane 0.01. Statistical analyses showed that samples from Kampala District (urban area, n=60) had significantly higher (p=0.0065) mean level of sum-DOT than those from Iganga District (rural area, n=83). Furthermore, samples from primiparae mothers (11=67) had significantly higher (p,=O_0016) mean level of sum-DDT than secundiparae mothers (n=76). There were no significant differences (p=7974) in mean levels of sum-DDT between vegetarian (n= 16) and non-vegetarian mothers (n= 127). No significant differences (p=0.5625) were also found in the mean levels of sum-DDT in the milk samples of mothers who ate fish (n~-=132) and those who did not (n= 11). The average estimated daily intake of surn-Df)'I' in this study was below the ADI of 0.02 mg/kg body weight set hy FAO/WHO (1985). However, in 28 (19.6%) individual samples, the estimated daily intakes of sum-DOT exceeded the set ADI. Furthermore, the average estimated daily intake of dieldrin in the study exceeded hy ahout 3 times the ADI of 0.0001 mg/kg body weight set by FAa/WHO (1978). One hundred and eight (75.5%) individual samples had dieldrin levels above the set ADI. On the other hand, the average estimated daily intake of lindane was below the ADI of 0.008 mg/kg body weight set hy FAa/WHO (1990). Generally, the mean levels of organochlorine residues detected in the Ugandan mothers' milk samples were low compared to those reported in other developing countries. However, they were highc: than those reported in industrialized countries. A total of 141 samples of cow milk samples were also collected from the same districts and analyzed for organochlorine residues. Sixty nine samples were collected from periurban areas of Kampala District, while 72 samples were collected from rural areas of Iganga District. The main objective was to identify, quantify and examine the toxicological significance of organochlorine residues levels in cow milk to the consumers. Out of all the samples anal) zed the following residues were found: p,p'-DDE (88.7%), dieldrin (87.2%), a-HCH ('8.3%). Jl,p'-DDD (l7.0%), p,p'-DDT (16.3%), o,p'-DDT (9.2%), B-HCH (7.\ %) and lindane (5.0%). Their mean levels in mg/kg milk fat were: sum-DDT 0.03, p,p'-DOE 0.02, p,p'-DDT 0.03, o,p'-DDT 0.02, p,p'-DDD 0.01, dieldrin 0.03, a-HCH o.ot, B-HCH 0.01 and lindane 0.01. The mean percent extractable milk fat was 4.3 %. In Kampala District, the observed mean levels of the residues in mg/kg milk fat in cow milk samples were: sum-DOT 0.04, p,p'-DDE 0.03, p,p'-DDT 0.02, o,p'-DDT 0.04, p,p'-DDD 0.01, dieldrin 0.04, lindane 0.02 and a-HCH 0.002. No quantifiahle residues levels of B-HCH were detected in samples from Kampala District. In Iganga District, mean levels of the residues in mg/kg milk fat were: sum-DDT 0.03, p,p'-DDE 0.01, p,p'-DDT 0.04, o,p'-DDT 0.02, p,p'-DDD 0.01, dieldrin 0.02, a-HCH 0.01, B-HCH 0.01 and lindane 0.02. Cow milk samples from the peri-urban areas (n = 69) had significantly higher (p=0.0018) mean level of sum-DOT than those from the rural areas (n=72). There were no significant differences (p=0.7443) in the mean sum-DOT levels between the local breeds (n=75) and exotic breeds (n=66) of cows. However, milk samples from zero-grazed cows (n=36) had significantly higher (p=0.0232) mean level ofsum-DDT than those from out-door grazed cows (n= 105). The mean levels of sum-DOT and dieldrin in cow milk samples in this study were helow the Maximum Residue Limits (MRLs) set hy FAa/WHO (1986). However, the mean level of lindane was slightly above the MRL. All the samples analyzed had sum- DDT levels helow MRL Only 2 (1.4%) samples had dieldrin levels ahove MRL and 4 (2.8%) samples had lindane levels above MRL. The levels of organochlorine residues in cow milk samples in this study had minimal health risks to the consumers. Despite the presence of organochlorine pesticide residues in Ugandan mothers milk, breast-feeding should he encouraged and promoted because ofhenefits of mothers' milk to the overal1 health and development on the infant. The findings of this study of the occurrence of organochlorine pesticide residues in mothers' and cow milk should he applied to introduce good agricultural practices in the use of these pesticides in Uganda. Farmers and pesticide dealers should he trained on guidelines on safe and effective pesticide use. In addition, strict legislation should he enforced on pesticides which are banned or restricted in the country so as minimize environmental pollution and human exposute to these toxic chemicals.