Drinking water quality, IL
Illinois contaminants ranked by SDWA exceedance
Which regulated contaminants exceed their maximum contaminant level (MCL) most often across Illinois'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 | - | 6,985 | 0 | 742 |
| 1,1-dichloroethylene | - | 6,994 | 0 | 742 |
| 1,2,4-trichlorobenzene | - | 6,990 | 0 | 742 |
| 1,2-dibromo-3-chloropropane | - | 4,453 | 0 | 603 |
| 1,2-dichloroethane | - | 6,988 | 0 | 742 |
| 1,2-dichloropropane | - | 6,990 | 0 | 742 |
| 2,4,5-tp | - | 4,493 | 0 | 605 |
| 2,4-d | - | 4,541 | 0 | 605 |
| alachlor | - | 4,990 | 0 | 603 |
| antimony, total | inorganic | 4,798 | 0 | 731 |
| arsenic | inorganic | 6,850 | 0 | 741 |
| asbestos | - | 46 | 0 | 45 |
| atrazine | - | 5,607 | 0 | 604 |
| barium | inorganic | 4,998 | 0 | 731 |
| 1,1,1-trichloroethane | - | 7,007 | 0 | 742 |
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.