2026 Q2 PFAS Compound Sampling Results
The following tables provide data on WSSC Water’s sampling results for per- and polyfluoroalkyl substances (PFAS) compounds, including both regulated and unregulated substances.
Potomac Filtration Plant
Sample date: April 2026
| PFAS | Result (ppt) | MCL/Health Reference Levels |
|---|---|---|
| 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS) | Not Detected | N/A1 |
| 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS) | Not Detected | N/A1 |
| 4,8-dioxa-3H-perfluorononanoic acid (ADONA) | Not Detected | N/A1 |
| hexafluoropropylene oxide dimer acid (HFPO DA) | Not Detected | 10 ppt (MCL) |
| nonafluoro-3,6-dioxaheptanoic acid (NFDHA) | Not Detected | N/A1 |
| perfluorobutanoic acid (PFBA) | 2.8 | 7,000 ppt5 |
| perfluorobutanesulfonic acid (PFBS) | 2.1 | 420-2,100 ppt2 |
| 1H,1H, 2H, 2H-perfluorodecane sulfonic acid (8:2FTS) | Not Detected | N/A1 |
| perfluorodecanoic acid (PFDA) | Not Detected | <20 ppt3 |
| perfluorododecanoic acid (PFDoA) | Not Detected | N/A1 |
| perfluoro(2-ethoxyethane)sulfonic acid (PFEESA) | Not Detected | N/A1 |
| perfluoroheptanesulfonic acid (PFHpS) | Not Detected | N/A1 |
| perfluoroheptanoic acid (PFHpA) | <1.6 | <20 ppt3 |
| 1H,1H, 2H, 2H-perfluorohexane sulfonic acid (4:2FTS) | Not Detected | N/A1 |
| perfluorohexanesulfonic acid (PFHxS) | <1.6 | 10 ppt (MCL) |
| perfluorohexanoic acid (PFHxA) | 2.4 | 400,000-560,000 ppt4 |
| perfluoro-3-methoxypropanoic acid (PFMPA) | Not Detected | N/A1 |
| perfluoro-4-methoxybutanoic acid (PFMBA) | Not Detected | N/A1 |
| perfluorononanoic acid (PFNA) | Not Detected | 10 ppt (MCL) |
| 1H,1H, 2H, 2H-perfluorooctane sulfonic acid (6:2FTS) | Not Detected | N/A1 |
| perfluorooctanesulfonic acid (PFOS) | 2.5 | 4 ppt (MCL) |
| perfluorooctanoic acid (PFOA) | 2 | 4 ppt (MCL) |
| perfluoropentanoic acid (PFPeA) | 4 | N/A1 |
| perfluoropentanesulfonic acid (PFPeS) | Not Detected | N/A1 |
| perfluoroundecanoic acid (PFUnA) | Not Detected | N/A1 |
| N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA) | Not Detected | N/A1 |
| N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA) | Not Detected | N/A1 |
| perfluorotetradecanoic acid (PFTA) | Not Detected | N/A1 |
| perfluorotridecanoic acid (PFTrDA) | Not Detected | N/A1 |
| Hazard Index = ( [HFPO-DAppt] /[10ppt] ) + ( [PFBSppt]/[2000ppt] ) + ( [PFNAppt] /[10ppt]) + ([PFHxSppt]/[10.0ppt]) | 0 | <1 |
| Lithium | Not Detected | N/A1 |
Definitions
ppt = parts per trillion. One part per trillion is equivalent to one drop of water in 20 olympic-sized swimming pools.
Not Detected : A compound is either not present or present at such low concentrations that it cannot be accurately detected by the analytical method.
MCL : maximum contamination limit
Hazard Index = ( [HFPO-DAppt] /[10ppt] ) + ( [PFBSppt]/[2000ppt] ) + ( [PFNAppt] /[10ppt]) + ([PFHxSppt]/[10.0ppt]) The Hazard Index (HI) is made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water to the highest level determined not to have risk of health effects. If the running annual average HI greater than 1.0, it is a violation of the proposed HI MCL.
Footnotes
1 N/A = not applicable; there are no accepted federal standards for these compounds
2 Michigan MCL of 420 ppt and 2,100 ppt Ohio EPA Action Level
3 Massachusetts MCL for the sum of the six PFAS compounds known as PFAS-6
4 Michigan MCL 400,000 ppt to 560,000 ppt Illinois health advisory level
5 Minnesota guidance value of 7,000 ppt
Patuxent Filtration Plant
Sample date: April 2026
| PFAS | Result (ppt) | MCL/Health Reference Levels |
|---|---|---|
| 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS) | Not Detected | N/A1 |
| 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS) | Not Detected | N/A1 |
| 4,8-dioxa-3H-perfluorononanoic acid (ADONA) | Not Detected | N/A1 |
| hexafluoropropylene oxide dimer acid (HFPO DA) | Not Detected | 10 ppt (MCL) |
| nonafluoro-3,6-dioxaheptanoic acid (NFDHA) | Not Detected | N/A1 |
| perfluorobutanoic acid (PFBA) | 2.3 | 7,000 ppt5 |
| perfluorobutanesulfonic acid (PFBS) | 1.7 | 420-2,100 ppt2 |
| 1H,1H, 2H, 2H-perfluorodecane sulfonic acid (8:2FTS) | Not Detected | N/A1 |
| perfluorodecanoic acid (PFDA) | Not Detected | <20 ppt3 |
| perfluorododecanoic acid (PFDoA) | Not Detected | N/A1 |
| perfluoro(2-ethoxyethane)sulfonic acid (PFEESA) | Not Detected | N/A1 |
| perfluoroheptanesulfonic acid (PFHpS) | Not Detected | N/A1 |
| perfluoroheptanoic acid (PFHpA) | <1.6 | <20 ppt3 |
| 1H,1H, 2H, 2H-perfluorohexane sulfonic acid (4:2FTS) | Not Detected | N/A1 |
| perfluorohexanesulfonic acid (PFHxS) | <1.6 | 10 ppt (MCL) |
| perfluorohexanoic acid (PFHxA) | 1.9 | 400,000-560,000 ppt4 |
| perfluoro-3-methoxypropanoic acid (PFMPA) | Not Detected | N/A1 |
| perfluoro-4-methoxybutanoic acid (PFMBA) | Not Detected | N/A1 |
| perfluorononanoic acid (PFNA) | Not Detected | 10 ppt (MCL) |
| 1H,1H, 2H, 2H-perfluorooctane sulfonic acid (6:2FTS) | Not Detected | N/A1 |
| perfluorooctanesulfonic acid (PFOS) | <1.6 | 4 ppt (MCL) |
| perfluorooctanoic acid (PFOA) | 1.8 | 4 ppt (MCL) |
| perfluoropentanoic acid (PFPeA) | 2.4 | N/A1 |
| perfluoropentanesulfonic acid (PFPeS) | Not Detected | N/A1 |
| perfluoroundecanoic acid (PFUnA) | Not Detected | N/A1 |
| N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA) | Not Detected | N/A1 |
| N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA) | Not Detected | N/A1 |
| perfluorotetradecanoic acid (PFTA) | Not Detected | N/A1 |
| perfluorotridecanoic acid (PFTrDA) | Not Detected | N/A1 |
| Hazard Index = ( [HFPO-DAppt] /[10ppt] ) + ( [PFBSppt]/[2000ppt] ) + ( [PFNAppt] /[10ppt]) + ([PFHxSppt]/[10.0ppt]) | 0 | <1 |
| Lithium | Not Detected | N/A1 |
Definitions
ppt = parts per trillion. One part per trillion is equivalent to one drop of water in 20 olympic-sized swimming pools.
Not Detected : A compound is either not present or present at such low concentrations that it cannot be accurately detected by the analytical method.
MCL : maximum contamination limit
Hazard Index = ( [HFPO-DAppt] /[10ppt] ) + ( [PFBSppt]/[2000ppt] ) + ( [PFNAppt] /[10ppt]) + ([PFHxSppt]/[10.0ppt]) The Hazard Index (HI) is made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water to the highest level determined not to have risk of health effects. If the running annual average HI greater than 1.0, it is a violation of the proposed HI MCL.
Footnotes
1 N/A = not applicable; there are no accepted federal standards for these compounds
2 Michigan MCL of 420 ppt and 2,100 ppt Ohio EPA Action Level
3 Massachusetts MCL for the sum of the six PFAS compounds known as PFAS-6
4 Michigan MCL 400,000 ppt to 560,000 ppt Illinois health advisory level
5 Minnesota guidance value of 7,000 ppt
Last Modified: June 3, 2026, 3:21 pm EDT