LEVELS OF CHLORINATED-HYDROCARBON RESIDUES IN CANADIAN HUMAN BREAST-MILK AND THEIR RELATIONSHIP TO SOME CHARACTERISTICS OF THE DONORS

A total of 412 breast milk samples from women in all provinces of Cana da were analysed for polychlorinated biphenyls, eight chlorinated benz enes, 2,3-dichloronaphthalene, Mirex, alpha, beta, gamma and delta hex achlorocyclohexane, alpha and gamma chlordane, oxychlordane, transnona chlor, p,p'-DDT and some analogues, heptachlor epoxide, dieldrin and o ctachlorostyrene. No delta-hexachlorocyclohexane, heptachlor or aldrin were found in any of the samples, while median levels of the 1,2,4- a nd 1,3,5-trichlorobenzene, 1,2,3,4- and 1,2,3,5-tetrachlorobenzenes, g amma chlordane, o,p'-DDT and octachlorostyrene were all less than the minimum detectable level (MDL). All other compounds were present at me dian levels ranging from < 0.1 to 7.2 ng/g whole milk, but did not occ ur in all samples. Di to tetrachlorobenzenes, except 1,2,4-trichlorobe nzene, 2,3-dichloronaphthalene and alpha-chlordane were observed in < 50% of the samples. From 1967 to 1986 a steady decline of hexachlorobe nzene, gamma-hexachlorocyclohexane, DDTs, heptachlor epoxide and dield rin was observed in Canadian breast milk. In addition, a decrease in s ome chlorinated benzenes, gamma-hexachlorocyclohexane and PCBs was als o observed between 1982 and 1986. Levels of oxychlordane and trans-non achlor remained constant. Canadian breast milk contamination appears t o be one of the lowest among the industrialized nations. Regional and provincial differences in residue levels appeared minimal, although mo re often samples from Quebec and British Columbia had higher levels of some contaminants, such as oxychlordane, than samples from other prov inces. No relationship was found between maternal age and residue leve ls, but some contaminants, such as PCBS, were significantly higher in the milk of mothers who breastfed their first child as compared to mul tiparous mothers. Breast milk residue levels were not related to fish consumption.