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.
Sample data. SYR4 ingest is in flight on prod; this page renders deterministic placeholder data until the V1 importer lands the IL cohort.
Top 5 contaminants by exceedance count
| Contaminant | Category | Samples | Above MCL | Munis affected |
|---|---|---|---|---|
| total trihalomethanes | disinfection byproduct | 1,240 | 78 | 37 |
| haloacetic acids (HAA5) | disinfection byproduct | 980 | 54 | 10 |
| lead | lead copper | 2,100 | 34 | 13 |
| arsenic | inorganic | 720 | 17 | 6 |
| nitrate (as nitrogen) | inorganic | 1,850 | 6 | 5 |
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.