Metadata analysis of persistent organic pollutants in national pools of human milk in support of the Stockholm convention implementation

A set of human milk samples, consisting of pools from up to 50 mothers that delivered their first baby was assessed for the persistent organic pollutants (POPs) listed in the Stockholm Convention. It must be noted that only samples that qualified for the criteria, as established in the global monitoring plan of the Stockholm Convention, following an initial protocol from the World Health Organization, were included. The data do not allow for an assessment of POP concentrations in breast milk with lactation period nor, in most
cases and when not indicated otherwise, a comparison within the same country. The assessment does not rank the POPs as to the risk for breastfeeding. Rather the measurements provide a basis for countries to compare among POPs or with other countries. A regional preference for certain POPs could not be identified; thus, taking into account global food supply chains and local production elsewhere does not allow us to prioritize a country for a certain POP. Although the highest concentrations were always found for the sum of DDT, these samples were not prominent in multivariate statistical analyses. The best indicator for the scale of POPs in breast milk was the sampling year: the earlier a national pool was created, the higher and the wider spread were the concentrations: see the example of dioxin-like POPs and indicator PCB. For some POPs, the income of a country seems to indicate scale and POP compounds. The population density was not found to be a suitable predictor or discriminator. Since all POPs seemed to level off and some POPs were only measured after the entry-into-force of the Stockholm
Convention in 2004, we do not have a strong indicator to determine POP concentrations in the 1980s or before.