Surface (raw) water samples were collected across Pennsylvania and tested for Per- and Polyfluoroalkyl Substances (PFAS) in summer 2019. Samples were collected from streams/rivers and Lake Erie sites.
Staff of the United States Geological Survey (USGS), Pennsylvania Department of Environmental Protection (DEP), and Susquehanna River Basin Commission (SRBC) collected discrete samples from all 178 of DEP's water quality network (WQN) stations in August 2019, led by staff from USGS's New Cumberland office. DEP staff collected passive water samples.
| Compound | Abbreviation | TOP Analysis |
|---|---|---|
| 11-chloroeicosafluoro-3-oxaundecane-1-sulfonate | 11Cl-PF3OUdS | |
| 4:2 fluorotelomersulfonate | 4:2 FTS | |
| 6:2 fluorotelomersulfonate | 6:2 FTS | |
| 8:2 fluorotelomersulfonate | 8:2 FTS | |
| 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate | 9Cl-PF3ONS | |
| 4-dioxa-3H-perfluorononanoate | ADONA | |
| Perfluoro-2-propoxypropanoate | HFPO-DA | |
| N-Ethylperfluorooctanesulfonamide | N-EtFOSA | |
| N-Ethylperfluorooctanesulfonamidoacetic acid | N-EtFOSAA | |
| N-Ethylperfluorooctanesulfonamidoethanol | N-EtFOSE | |
| N-Methylperfluorooctanesulfonamide | N-MeFOSA | |
| N-Methylperfluorooctanesulfonamidoacetic acid | N-MeFOSAA | |
| N-Methylperfluorooctanesulfonamidoethanol | N-MeFOSE | |
| Perfluorobutanoate | PFBA | X |
| Perfluorobutanesulfonate | PFBS | X |
| Perfluorodecanoate | PFDA | X |
| Perfluorododecanoate | PFDoA | X |
| Perfluorododecanesulfonate | PFDoS | X |
| Perfluorodecanesulfonate | PFDS | X |
| Perfluoroheptanoate | PFHpA | X |
| Perfluoroheptanesulfonate | PFHpS | X |
| Perfluorohexanoate | PFHxA | X |
| Perfluorohexanesulfonate | PFHxS | X |
| Perfluorononanoate | PFNA | X |
| Perfluorononanesulfonate | PFNS | X |
| Perfluorooctanoate | PFOA | X |
| Perfluorooctanesulfonate | PFOS | X |
| Perfluorooctanesulfonamide | PFOSA | |
| Perfluoropentanoate | PFPeA | X |
| Perfluoropentanesulfonate | PFPeS | X |
| Perfluorotetradecanoate | PFTeDA | X |
| Perfluorotridecanoate | PFTrDA | X |
| Perfluoroundecanoate | PFUnDA | X |
Polar organic chemical integrative samplers (POCIS) were deployed at 18 sites across Pennsylvania and analyzed for the 33 PFAS chemicals listed in the table above. POCIS are comprised of microporous polyethersulfone membranes with a solid phase sorbent (Oasis HLB) that samples hydrophilic contaminants. The samplers are placed in the field for approximately one month and are capable of detecting low-level contaminants or contamination that occurs infrequently and may be missed by traditional discrete samples. The passive samples were analyzed at SGS AXYS Analytical Services Ltd. in British Columbia, Canada using SGS AXYS Method MLA-110.
Raw results from POCIS are reported as ng/POCIS filter. Time-weighted average (TWA) concentrations (ng/L) can be calculated for compounds that have lab-derived sampling rates (Rs). Rs values were available for PFBS, PFOS, PFOA, PFHxA, PFNA, PFDA, and PFDoA. These chemicals are reported in ng/L for POCIS samples.
PFOS and PFOA in WQN discrete samples and in POCIS samples were summed for purposes of mapping sample results. When TOP was higher than the original PFAS result, TOP value was used.
Highest PFOS + PFOA discrete water concentrations were found at WQN stations 121 (Neshaminy Creek), 154 (Valley Creek near Valley Forge), and 193 (Wissahickon Creek). However, all PFOS + PFOA results were below the drinking water lifetime health advisory level for PFOS + PFOA of 70 ng/L established by the United States Environmental Protection Agency (EPA) in 2016. In comparing these results to the EPA drinking water lifetime health advisory level, it is important to note again that these were samples of raw surface water, not samples of finished drinking water, and that different laboratory methods were used to analyze PFAS in these raw surface water samples than EPA's laboratory methods for analyzing PFAS in drinking water samples. The highest PFOS + PFOA TWA concentration was 212 ng/L at WQN 121 (Neshaminy Creek). POCIS TWA concentrations for PFOS + PFOA were higher than the PFOS + PFOA concentrations in discrete water samples at all sites where both types of samples were collected, and detectable TWA concentrations of PFOS + PFOA were observed in some POCIS samples from sites where PFOS + PFOA concentrations were not detecable in the discrete samples. Direct comparison of TWA concentrations to discrete sample concentrations is not generally recommended since the TWA concentrations are estimated concentrations. However, comparing the TWA concentrations to the discrete sample concentrations does illustate the sensitivity of POCIS sampling and the ability of passive sampling to detect chemicals that may not be picked up in a discrete sample.
Total PFAS concentrations were calculated by summing the detected concentrations of PFBS, PFOS, PFOA, PFHxA, PFNA, PFDA, and PFDoA in WQN discete samples and in POCIS samples. These seven PFAS were used to calculate total PFAS concentrations for this map because these are the seven chemicals for which TWA concentrations could be calculated in the POCIS samples, as described above, thus allowing for comparison of total PFAS concentrations between POCIS samples and discrete samples. When TOP was higher than the original PFAS result, TOP value was used.
Highest total PFAS concentrations (PFBS +, PFOS, + PFOA, + PFHxA, + PFNA, + PFDA, + PFDoA) in discrete samples were observed at WQN stations 121 (Neshaminy Creek), 154 (Valley Creek near Valley Forge), and 193 (Wissahickon Creek). The highest total PFAS TWA concentration was 242 ng/L at WQN 121 (Neshaminy Creek).
Total number of PFAS chemicals detected out of the 33 tested were also mapped. Again, if TOP analysis resulted in a discrete sample detection while the initial analysis did not, the TOP result was counted. While the sites with the highest total PFAS and PFOS + PFOA concentrations did have the highest number of PFAS chemicals detected, it is worth noting that many sites with very low level detections had a fairly high number of compounds detected, for example, at WQN 281 (Paxton Creek); this pattern was observed in discrete samples and in POCIS samples. The highest number of PFAS detections in discrete samples was 10, occurring at several sites, including WQN 121 (Neshaminy Creek), WQN 154 (Valley Creek near Valley Forge), and WQN 193 (Wissahickon Creek). The highest number of detections in POCIS samples was 18, occurring at WQN 123 (Lehigh River) and 101 (Delaware River at Trenton).
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