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The concentrations of selected organochlorine contaminants in Swedish human milk have been determined in a number of studies conducted at the National Food Administration during the 1980s. It was shown that the time of sampling post-partum (subsequent to childbirth) had little effect on the levels of the DDT complex, beta-HCH, HCB and PCBs in breast milk fat. However, the levels of these compounds decreased with increasing parity (number of children born). For this reason it is recommended that primiparae (women nursing their first child) be sampled when comparing levels over time and in milk from mothers from different geographical areas. The levels of organochlorine compounds in the fat of breast milk from primiparae living in different parts of Sweden were similar. Finally, a study on time trends in concentrations of these compounds in milk from mothers living in Uppsala showed that a marked decline in levels has taken place during the 1980s.

The organochlorine contaminant (OCC) data generated by the Swedish National Food Administration (NFA) since 1973 has been utilized to calculate average Swedish dietary intakes. Direct food consumption statistics based on the yearly per capita Swedish consumption of five principal food groups has been used with OCC levels over 5-year periods, up to 1992. The present study shows the decline in OCC dietary intakes between 1975 and 1990. It is suggested that this is principally because of a decline in OCC concentrations in foods of animal origin rather than because of changes in food consumption patterns. The estimated intakes for the DDT complex, HCH isomers, dieldrin and HCB are generally well below the ADIs established by FAO/WHO. For total PCBs, no such ADI/TDI has been set up, either by FAO/WHO or in a Nordic PCB risk assessment. However, when compared with a US FDA guideline, the average Swedish total PCB dietary intake in 1990 is approximately 10-fold lower. Finally, this study shows the good relationship between OCC dietary intakes via foods of animal origin and the concentrations measured on a fat weight basis in Swedish human milk.

The levels of polychlorinated biphenyls (PCBs) in human milk provide an index of exposure of the mother to these compounds and enable the intake by the breast-fed child to be estimated. For valid comparisons between different studies, concentrations should be expressed on a milk fat basis. In a recently completed UNEP/WHO pilot project on monitoring of organochlorine compounds in human milk in ten countries, great emphasis was placed on analytical quality assurance. To obtain comparable data, a common procedure, that of Sawyer, was adopted for quantitation of PCBs, using Aroclor 1260 as standard. In addition, certain criteria (e.g., age and parity) were established for selection of the mothers to be sampled. In contrast to the situation with p,p'-DDT and p,p'-DDE, the levels of PCBs in human milk fat were higher in the European countries and Japan than in China, India and Mexico. In fact, PCBs were not detected in human milk in the latter three countries. Although PCBs were detected in some samples in the USA, the median level was below the limit of detection of the method used there (1 mg/kg fat). The median PCB levels reported from Belgium, Israel, Japan and Yugoslavia were 0.81, 0.45, 0.35 and 0.63 mg/kg fat, respectively. Higher median levels were reported from Sweden and the Federal Republic of Germany (0.97 and 2.1 mg/kg fat, respectively). The German samples were not analyzed by the Sawyer method.

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