emporal trends of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) were assessed using 86 pooled human milk samples from 59 countries from all United Nations Regional Groups collected between 2008 and 2019 as part of the WHO/UNEP-coordinated exposure studies. The primary objective of these temporal studies is to provide monitoring data for the effectiveness evaluation of the Stockholm Convention on Persistent Organic Pollutants (POPs). General temporal trends were estimated using data from all participating countries by grouping into three equal four-year periods (2008–2011, 2012–2015, and 2016–2019) reflecting the performance of three rounds of the studies. A more precise approach is the use of data from 24 countries with repeated participation in the WHO/UNEP-coordinated exposure studies, 22 of them in different periods and two in the same period. However, there were no Western European countries with multiple participation, and only two countries from the Asia-Pacific Region with one country submitting two samples in the same period.