Outside the Safe Operating Space of a New Planetary Boundary for Per- and Polyfluoroalkyl Substances (PFAS)

Abstract

It is hypothesized that environmental contamination by per- and polyfluoroalkyl substances (PFAS) defines a separate planetary boundary and that this boundary has been exceeded. This hypothesis is tested by comparing the levels of four selected perfluoroalkyl acids (PFAAs) (i.e., perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA)) in various global environmental media (i.e., rainwater, soils, and surface waters) with recently proposed guideline levels. On the basis of the four PFAAs considered, it is concluded that (1) levels of PFOA and PFOS in rainwater often greatly exceed US Environmental Protection Agency (EPA) Lifetime Drinking Water Health Advisory levels and the sum of the aforementioned four PFAAs (Σ4 PFAS) in rainwater is often above Danish drinking water limit values also based on Σ4 PFAS; (2) levels of PFOS in rainwater are often above Environmental Quality Standard for Inland European Union Surface Water; and (3) atmospheric deposition also leads to global soils being ubiquitously contaminated and to be often above proposed Dutch guideline values. It is, therefore, concluded that the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded. Levels of PFAAs in atmospheric deposition are especially poorly reversible because of the high persistence of PFAAs and their ability to continuously cycle in the hydrosphere, including on sea spray aerosols emitted from the oceans. Because of the poor reversibility of environmental exposure to PFAS and their associated effects, it is vitally important that PFAS uses and emissions are rapidly restricted.

Keywords: PFAS; chemical pollution; environmental exposure; planetary boundary.

Figure 1

Levels of (A) PFOA, (B) PFOS, and (C) Σ4 PFAAs (PFOA + PFNA + PFHxS + PFOS) in wet deposition collected at various global locations from 2010 to the present. For one study, it was not possible to derive median values and thus mean values are provided (indicated by *). The dashed line in (A) shows the US EPA health advisory for PFOA (0.004 ng/L), the dashed lines in (B) show the EU EQC for PFOS (i.e., 0.65 ng/L) and the US EPA health advisory for PFOS (i.e., 0.020 ng/L), and the dashed line in (C) shows the Danish drinking water guideline for Σ4 PFAAs (i.e., 2 ng/L). Bars indicate median values, and the uncertainty bars indicate minimum and maximum values. Wet deposition measurements for Σ4 PFAAs are ordered from high to low (from left to right) and sorted into four categories (“Fluoropolymer plant” indicates that samples were taken close to a fluoropolymer manufacturing plant; “Urban” indicates that samples were taken in cities or urbanized regions; “Rural” indicates that samples were taken in rural less-populated locations, and “Remote” indicates that samples were taken in regions with very low or nonexistent human populations). Some studies sampled wet deposition in multiple locations within one of the four categories, and thus data from these individual locations are grouped together in several bars. The raw data and a description of data treatment for figure preparation are provided in the Supporting Information.