Reference
The contaminants in EPA's records
EPA's national survey tested for 29 PFAS and lithium. Lead and copper are measured separately, at customer taps. Each page explains what the substance is, what EPA's limit or guidance value means, and which water systems reported the highest results.
In focus32Contaminant reference pages
Public records. Clearer context.
| Contaminant | Type | Federal status | Systems tested | Systems where it was found | EPA reference |
|---|---|---|---|---|---|
| PFOA | PFAS | MCL (2024 PFAS rule) | 10,307 | 1,305 | 4.0 ppt |
| PFOS | PFAS | MCL (2024 PFAS rule) | 10,307 | 1,352 | 4.0 ppt |
| PFHxS | PFAS | MCL (2024 rule); rescission proposed May 2026 | 10,307 | 1,037 | 10.0 ppt |
| PFNA | PFAS | MCL (2024 rule); rescission proposed May 2026 | 10,307 | 83 | 10.0 ppt |
| HFPO-DA (GenX) | PFAS | MCL (2024 rule); rescission proposed May 2026 | 10,307 | 48 | 10.0 ppt |
| PFBS | PFAS | No individual MCL; hazard-index component (rescission proposed May 2026) | 10,307 | 1,707 | 2,000 ppt |
| PFBA | PFAS | Unregulated; screening level only | 10,307 | 1,935 | 6,000 ppt |
| PFHxA | PFAS | Unregulated; screening level only | 10,307 | 1,807 | 3,000 ppt |
| PFPeA | PFAS | Unregulated | 10,307 | 2,066 | none set |
| PFHpA | PFAS | Unregulated | 10,307 | 555 | none set |
| PFDA | PFAS | Unregulated | 10,307 | 17 | none set |
| PFUnA | PFAS | Unregulated | 10,307 | 6 | none set |
| PFDoA | PFAS | Unregulated | 10,307 | 4 | none set |
| PFTrDA | PFAS | Unregulated | 10,309 | 0 | none set |
| PFTA | PFAS | Unregulated | 10,309 | 0 | none set |
| PFPeS | PFAS | Unregulated | 10,307 | 50 | none set |
| PFHpS | PFAS | Unregulated | 10,307 | 5 | none set |
| 4:2 FTS | PFAS | Unregulated | 10,307 | 3 | none set |
| 6:2 FTS | PFAS | Unregulated | 10,307 | 183 | none set |
| 8:2 FTS | PFAS | Unregulated | 10,307 | 10 | none set |
| ADONA | PFAS | Unregulated | 10,307 | 3 | none set |
| 9Cl-PF3ONS | PFAS | Unregulated | 10,307 | 1 | none set |
| 11Cl-PF3OUdS | PFAS | Unregulated | 10,307 | 0 | none set |
| NEtFOSAA | PFAS | Unregulated | 10,309 | 1 | none set |
| NMeFOSAA | PFAS | Unregulated | 10,309 | 1 | none set |
| NFDHA | PFAS | Unregulated | 10,307 | 4 | none set |
| PFEESA | PFAS | Unregulated | 10,307 | 0 | none set |
| PFMPA | PFAS | Unregulated | 10,307 | 2 | none set |
| PFMBA | PFAS | Unregulated | 10,307 | 1 | none set |
| Lithium | metal | Unregulated; EPA health reference level | 10,313 | 3,773 | 10 ppb |
| Lead | metal | Action level 15 µg/L (Lead and Copper Rule); 10 µg/L under the 2024 LCRI from 2027 | tap monitoring | — | 15 ppb |
| Copper | metal | Action level 1,300 µg/L (Lead and Copper Rule) | tap monitoring | — | 1,300 ppb |