Mother's milk protein profile, a possible biomarker for human exposure to persistent insecticides

The electrophoretic protein profile and residue levels of selected persistent insecticides were investigated in 160 mother's milk samples representing 20 different locations in Egypt. Nine major protein bands were detected in all of the samples. These protein bands were designated as lactoferrin, albumin, SIgA heavy chain, casein I, casein II, SIgA light chain, casein III, lysozyme and alpha-lactalbumin. Residue levels of DDT and its metabolites as well as lindane and its other hexachlorocyclohexane isomers were determined using electron capture gas chromatography and confirmed by gas chromatography/mass spectrometric analysis. Samples containing relatively higher residue levels of the DDT group (DDT, DDE and DDD) showed significant effects on the levels of lysozyme and alpha-lactalbumin bands relative to samples with low or no residue levels. On the other hand, the casein subunits were mostly affected by the residue levels of hexachlorocyclohexane isomers (alpha, beta, gamma and delta isomers). The two patterns showed characteristic dose response correlation suggesting that the protein profile of human milk may serve as a quick biomarker for exposure to persistent insecticides.