Drinking water quality, WI
Wisconsin contaminants ranked by SDWA exceedance
Which regulated contaminants exceed their maximum contaminant level (MCL) most often across Wisconsin's community water systems, per EPA's Six-Year Review sample-level dataset (2012-2019). Source data is public; every value is citable.
Top 15 contaminants by exceedance count
| Contaminant | Category | Samples | Above MCL | Munis affected |
|---|---|---|---|---|
| 1,1,2-trichloroethane | - | 11,512 | 0 | 688 |
| 1,1-dichloroethylene | - | 11,512 | 0 | 688 |
| 1,2,4-trichlorobenzene | - | 11,512 | 0 | 688 |
| 1,2-dibromo-3-chloropropane | - | 368 | 0 | 192 |
| 1,2-dichloroethane | - | 11,513 | 0 | 688 |
| 1,2-dichloropropane | - | 11,513 | 0 | 688 |
| 2,3,7,8-tcdd | - | 110 | 0 | 61 |
| 2,4,5-tp | - | 3,777 | 0 | 687 |
| 2,4-d | - | 3,778 | 0 | 687 |
| alachlor | - | 3,808 | 0 | 687 |
| antimony, total | inorganic | 5,231 | 0 | 688 |
| arsenic | inorganic | 6,347 | 0 | 688 |
| asbestos | - | 31 | 0 | 26 |
| atrazine | - | 3,848 | 0 | 687 |
| 1,1,1-trichloroethane | - | 11,519 | 0 | 688 |
For citizens
Look up your own water system by name on the muni search, then read the drinking-water quality band on its profile page for per-contaminant readings + MCL ratios.
For chemical suppliers
Contaminants near or above MCL signal treatment-chemical procurement pressure. Lane intelligence pairs this with per-chemical bid timing on the supplier tier.