WHO- and UNEP-Coordinated Human Milk Studies 2000–2019: Findings of Chlorinated Paraffins

Abstract

Chlorinated paraffins (CP) are complex mixtures of several million theoretically possible individual compounds. Contrary to medium-chain CP (MCCP, C14–C17) and long-chain CP (LCCP, C18–C30), the third sub-group investigated, short-chain chlorinated paraffins (SCCP, C10–C13), have been listed in 2017 in Annex A (Elimination) of the Stockholm Convention on Persistent Organic Pollutants. The concentrations of CP were determined in 84 nation-wide pooled human milk samples collected between 2009 and 2019 in 57 countries participating in exposure studies coordinated by the World Health Organization and the United Nations Environment Programme. Until 2015, only total CP content was determined. In light of on-going efforts to also add other CP groups to the Annexes of the Stockholm Convention and the glaring lack of data on the general background contamination worldwide, later analysis determined SCCP and MCCP and investigated the presence of LCCP (C18–C20 only). CP were present in all 84 samples, ranging 8.7–700 ng/g lipid. A statistically significant increase rate of total CP concentrations in human milk of 30% over 10 years was found on a global level, with a considerable variation between UN Regional Groups. Homologue group patterns indicated higher shares of MCCP and LCCP in industrialized countries and economically dependent areas. Compared to all other POPs analysed in the samples, the concentration of the sum of SCCP and MCCP was in most cases only surpassed by DDT, except European countries with high shares of PCB. Considering the ubiquitous presence of CP in humans worldwide, further investigation into toxicological effects and human exposure seems more pressing than ever, so that regulatory action may follow.