Total Trihalomethanes (TTHM)
Unresolved Total Trihalomethanes Rule violation cited in 2025 (total trihalomethanes (tthm)).
PWSID IL0315617 · Purchased / wholesaleFederal
60 people served. No health-based SDWIS violations recorded in the past 5 years. 4 remain unresolved. Last cited 1 year ago.
Unresolved Total Trihalomethanes Rule violation cited in 2025 (total trihalomethanes (tthm)).
Unresolved Total Trihalomethanes Rule violation cited in 2025 (total trihalomethanes (tthm)).
Unresolved Total Trihalomethanes Rule violation cited in 2025 (haloacetic acids (haa5)).
Unresolved Total Trihalomethanes Rule violation cited in 2025 (haloacetic acids (haa5)).
Health-based violations exceed an MCL or treatment-technique standard. Monitoring violations are reporting failures with no measured exceedance — they tell you the system isn't fully transparent, not that the water is unsafe today.
Failure to monitor as scheduled
Failure to monitor as scheduled
Failure to monitor as scheduled
Failure to monitor as scheduled
OTHER; returned to compliance
OTHER; returned to compliance
OTHER; returned to compliance
OTHER; returned to compliance
OTHER; returned to compliance
Cook County, Illinois (utility's served county per SDWIS GEOGRAPHIC_AREA — city-level not yet matched): a service population of 5,225,367. Local disparity score for pm2.5 (fine particulate) sits moderately above the reference (128). Why we surface this →
Low-income
People of color
Under age 5
Over age 64
| Indicator | Disparity score | Reading |
|---|---|---|
| PM2.5 (fine particulate) | 128 | moderately above the reference |
| Ozone | 136 | moderately above the reference |
| Nitrogen dioxide (NO₂) | 150 | well above the reference burden |
| Diesel particulate | 141 | moderately above the reference |
| Toxic releases (RSEI) | 145 | moderately above the reference |
| Traffic proximity | 134 | moderately above the reference |
| Lead-paint risk (pre-1960 housing) | 118 | moderately above the reference |
| Superfund site proximity | 104 | near the reference |
| RMP-facility proximity | 136 | moderately above the reference |
| Hazardous-waste site proximity | 129 | moderately above the reference |
| Underground storage tanks | 128 | moderately above the reference |
| NPDES wastewater proximity | 147 | moderately above the reference |
| Drinking-water non-compliance | 12 | well below the reference |
Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror).
Source. EPA Safe Drinking Water Information System · retrieved 2026-05-07. Reporting period 2020-01-01 → 2026-05-07.
What this is not. SDWIS records compliance against federal MCLs — not a direct readout of tap-water concentrations. Active health-based violations are not the same as a current crisis; we link to the EPA record so you can verify return-to-compliance status before forming a conclusion.