Stories of Global Chemical Pollution: Will We Ever Understand Environmental Persistence?

R ecently, Cousins et al. 1 compared the levels of four perfluoroalkyl acids (PFAAs), PFOA, PFNA, PFOS, and PFHxS, in rainwater from various regions of the world with health advisories or environmental quality standards (EQSs) for these PFAAs.The health advisories and EQSs were recently released or updated and reflect the latest findings on the health impacts of the four PFAAs.Cousins et al. found that the levels of PFOA and PFOS in rainwater exceed the U.S. Environmental Protection Agency (U.S. EPA) drinking water health advisories for PFOA in all, and for PFOS in most, of the 16 regions considered, in many cases by >1 or even 2 orders of magnitude.This means that there is now a global PFAA footprint that is well visible with current analytical methods and also relevant in terms of possible health impacts.Cousins et al. also pointed out that it is the extreme persistence of PFAAs that has caused this problem of a global PFAA footprint (of course, in combination with PFAA emissions over many years) and that this footprint will not disappear any time soon.The paper by Cousins et al. quickly received a great deal of attention and, within 5 weeks, had been covered more than 280 times by the media (more than 200 000 views and a very high Altmetric score of >2800).As co-authors of the paper, we did not expect such a massive response and interest, and in light of this response, we would like to initiate a discussion about the basic problem that we addressed in our paper.Importantly, similar situations of global chemical pollution were already reported in the second half of the 20th century (see Figure 1).DDT was found to bioaccumulate in marine mammals in the Baltic 2 and to undergo long-range environmental transport. 3Polychlorinated biphenyls (PCBs) were found in marine mammals, soils, air, seawater, freshwater, and precipitation around the world from the late 1960s on, 2,4,5 and their impacts on humans and wildlife can still be felt today. 6Chlorofluorocarbons (CFCs) were predicted to cause stratospheric ozone depletion in 1974 7 and were detected in the troposphere and also in seawater globally; 8 the stratospheric ozone hole was experimentally confirmed in 1985. 9ike PFAAs, these chemicals caused global chemical pollution footprints.Also in their cases, the main factor that led to the global scale of the problem was the high