Persistent organic pollutants in human milk from primiparae – correlations, global, regional, and national time-trends

Human breast milk reflects body burden of chemicals and has been used for exposure assessment to estimate risks of humans from pollutants. Harmonized protocols for sampling and analysis of persistent organic pollutants (POPs) have become widely available after the entry-into-force of the Stockholm Convention on POPs and activities coordinated by the United Nations Environment Programme (UNEP). These protocols promote the generation of national pools consisting of breast milk from first mothers directed to assess at national level but have not been assessed comprehensively. Early surveys date back to the mid-1980s, but the majority of the pools and high numbers of POPs analytes were available after the year 2000. Our assessment of pools from 90 countries for 29 POPs showed declining time trends for almost all POPs and significant differences between all 5-year time periods. However, in general, the most recent data from samples collected between 2015 and 2019, were no longer different from the period immediately prior. The strongest declines were seen for POPs that have already been measured for more than 30 years, i.e., dioxin-like POPs and polychlorinated biphenyls (PCB). For certain initial and newly listed POPs, such as aldrin, endrin, mirex, toxaphene, α-HCH, chlordecone, endosulfan, pentachlorobenzene, hexachlorobutadiene, decabromo diphenyl ether, hexabromobiphenyl 153, and perfluorohexane sulfonate, the median values in pools were always zero, and some of them were never quantified in these human milk pools. Since these POPs may be present at national level, we recommend including all listed POPs into surveys related to the Stockholm Convention.