Overview of WHO- and UNEP-Coordinated Human Milk Studies and Their Link to the Stockholm Convention on Persistent Organic Pollutants

Abstract Building on the two rounds of human exposures studies coordinated by the World Health Organization (WHO) in the mid-1980s and 1990s to determine the concentrations of polychlorinated biphenyls, polychlorinated dibenzo- p -dioxins, and polychlorinated dibenzofurans in human milk, five further studies were performed between 2000 and 2019. Following the entering into force of the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2004, WHO and the United Nations Environment Programme (UNEP) agreed to collaborate in joint studies. The collaboration aimed at supporting the Convention’s implementation by assessing its effectiveness as required under Article 16. It expanded the number of analytes in the studies to include the initial 12 POPs targeted by the Convention for elimination or reduction and subsequently to the 30 POPs covered under the Stockholm Convention as of 2019, furthermore two POPs proposed for listing. The implementation of the studies has followed three basic steps: (1) collection of a large number of individual samples from mothers based on the standardized WHO/UNEP protocol; (2) from equal amounts of the individual samples, preparation of pooled samples that are considered to represent the average levels of POPs in human milk for a country or subpopulation of that country at the time of sampling; and (3) analysis of POPs in the pooled samples by the Reference Laboratories for the WHO/UNEP-coordinated exposure studies 2000–2019 (for chlorinated and brominated POPs in the period 2000–2019 at CVUA Freiburg, Germany, and for perfluoroalkane substances in the period 2009–2019 at Örebro University, Sweden). In studies between 2000 and 2019, 82 countries from all United Nations regions participated, with 50 countries participating in more than one study. Repeated participation of countries permits the assessment of temporal trends, which can be used for risk management purposes as well as the evaluation of the effectiveness of the Convention in eliminating or reducing emissions of POPs.