Perfluoroalkyl substances (PFASs) in the Maltese environment

Abstract

The extent of the occurrence of perfluoroalkyl substances (PFASs) in the Maltese environment in different matrices including natural and processed waters, valley sediments and soil, as well as fruit and vegetables was investigated here for the first time. PFASs were extracted from the different environmental matrices using solid phase extraction and the extracts were then analysed using ultra performance liquid chromatography coupled to mass spectrometry in tandem (UPLC-MS/MS). PFAS contamination was found in 100% of rainwater and surface water samples with PFHpA (0.29 ng/L – 0.38 ng/L) and PFOA (ND – 0.68 ng/L) being the two major PFASs detected for rainwater and PFOS (<LOD – 8.6 ng/L) and PFOA (ND – 16 ng/L) being the two major PFASs detected for surface water. Analysis of wind trajectories on the days leading to the rain events revealed that that the highest concentrations of PFASs are found in rainwater originating from the north of the Maltese Islands. All sediment, soil and groundwater samples were contaminated with at least one PFAS. PFASs having more than 7 carbons were the predominant ones in sediment and soil being, PFOS (<LOQ – 5.91 ng/g), PFOA (<LOQ – 0.58 ng/g), and PFDA (LOQ – 1.05 ng/g) found in 100% of the samples. Meanwhile PFOA (<LOD – 2.68 ng/L) was the PFAS detected in all groundwater samples, while PFDA was not detected in any of the groundwater samples. The concentrations of PFASs observed in groundwater on the Maltese Islands were below the parameters set by the Directive 98/83/EC. All seawater samples (except one) were contaminated with at least one PFAS. PFOA (<LOD – 458 pg/L) and PFOS (<LOD – 471 pg/L) were the two major PFASs being detected in 98 % and 92 % of the surface waters respectively. The most contaminated seawater samples were from areas of high human activity which were enclosed. Wastewater samples from treatment plants were also found to be contaminated with at least one PFAS. PFOA was predominant and its concentrations ranged from 7.33 to 13.06 ng/L and 8.37 to 10.07 ng/L in influent and effluent, respectively. PFOS was the second dominant PFAS in wastewater with levels from 2.68 to 3.97 ng/L and 0.49 to 4.76 ng/L in influent and effluent, respectively. Low levels of the PFASs tested for, were detected in all vegetables and fruits investigated ranging from ND to 173 pg/g. Low levels of PFASs were also detected in drinking water (tap water and bottled water) ranging from ND to 1.25 ng/L. It was observed that in drinking water where water is sourced from seawater (through reverse osmosis), no PFASs were detected in quantifiable amounts demonstrating that exposure to PFASs through drinking water in Malta is dependent on the source. The results of this research project have shown that PFASs are widely distributed in the Maltese environment despite having no industrial sources and despite being ‘remote’ with no land connection to any other mainland. This is reflected in the low PFAS concentrations obtained when compared to concentrations in studies about presence in mainland Europe. Contamination of the environment in Maltese Islands by PFASs is influenced by atmospheric transport as well as the disposal of imported materials contaminated by PFASs.