Global Priority Perfluoroalkyl Substances in Surface Waters:Establishing Baseline Levels on Regional Basis
By Abeer Baabish
August 28, 2019
Perfluorooctane sulfonic acid (PFOS) has been regulated under Stockholm Convention in 2009, perfluorooctanoic acid (PFOA) was listed in 2019. Perfluorohexane sulfonic acid (PFHxS) is under review and could be included in 2021. There are still permitted uses of these three chemicals, but it is expected that the production and application will decrease as a result of the international regulation and the environmental concentrations of PFOS, PFOA and PFHxS are expected to decline. However, without a reference point, it is difficult to judge if the levels are decreasing or not. Therefore, baseline levels of PFOS, PFOA and PFHxS in one of United Nations Environment Programme (UNEP) core matrices, surface water, were established with the support of samples collected from Africa (n=34), Asia (n=11), Group of Latin America and Caribbean (GRULAC) (n=35) and Pacific Islands (n=25) under a period of two years. The baseline levels were set as the median concentration (ng/L) in each region (interquartile range) based on a variance test (Kruskal-Wallis) and descriptive statistical testing.
Baseline levels for ΣPFOS, PFOA and PFHxS including all countries in Africa (n=6) was set at 0.38 (0.18 – 0.54) ng/L, 0.26 (0.13 – 0.80) ng/L and 0.042 (0.02 - 0.09) ng/L respectively, and excluding Kenya and Tunisia (n=4) at 0.22 (0.10 – 0.38) ng/L for ΣPFOS , 0.18 (0.10 – 0.25) ng/L for PFOA and 0.031 (0.02 – 0.04) ng/L for PFHxS.
In Pacific Islands the baseline levels for ΣPFOS, PFOA and PFHxS were established at 0.15 (0.04 – 1.24) ng/L, 0.046 (0.03 – 0.11) ng/L and 0.055 (0.01 – 0.63) ng/L including all countries (n=7), and 0.053 (0.03 – 0.15) ng/L, 0.033 (0.03 – 0.04) ng/L and 0.012 (0.01 – 0.05) ng/L excluding Vanuatu and Kiribati (n=5).
In Asia and Group of Latin America samples were in similar concentrations range within the region, so baseline levels for ΣPFOS, PFOA and PFHxS in Asia were set at 0.048 (0.04 - 0.12) ng/L, 0.11 (0.07 – 0.19) ng/L and 0.018 (0.01-0.03) ng/L, and in GRULAC at 1.31(0.39 – 1.88) ng/L, 0.50 (0.28 – 0.71) ng/L and 0.14 (0.06 – 0.44) ng/L for the three priority PFASs respectively.
The importance of the three PFASs in relation to other measured Σ73 PFASs were assessed in selected samples (n=12) including six samples from Sweden. The results showed a contribution of 10% to 48% of the sum of the three priority PFASs to all 27 detected PFASs.It is not clear whether a total of 73 PFASs is enough to explain the environmental contamination of PFASs and therefore the extractable organofluorine (EOF) was measured in selected samples (n=12). Due to the high EOF levels in procedural blanks, only two out of twelve samples were used to assess the contribution of detected PFASs to EOF. The contribution of 27 detected PFASs to EOF were 3% for Vanuatu and 5% for Sweden (Svartån). The contribution of the sum of the three PFASs to EOF accounted for 1.1% for Vanuatu and 1.4% for Svartån. Nevertheless, within the organofluorine fraction, a major percentage 95% to 97% of fluorine remains unknown in water samples, suggesting the occurrence of other organofluorine substances.
At the same time, some newly identified PFAS (novel PFASs) that are known to replace PFOS and PFOA in different applications were detected in surface water samples collected from Sweden (n=6) and from developing countries under UNEP/GMP2 project (n=6). Perfluoroethylcyclohexane sulfonate (PFECHS) was detected in four samples in concentrations ranging between 0.03 and 0.14 ng/L. Perfluoro-2-propoxypropanoic acid (HFPO-DA) was detected in three samples in the concentration range 0.03-0.06 ng/L.