What TTHM is, and why it's regulated
What the EPA limit means
80 µg/L
Maximum Contaminant Level — the enforceable ceiling a supplier must stay under.
—
Health goal (MCLG) — the level with no known health effect. It is a goal, not a legal limit, and is often zero for carcinogens.
SYR4
Where these measurements come from. Hover the tag for the EPA programme and years.
Where TTHM was found
The water suppliers reporting the highest levels, worst first.
| Supplier | City | State | Level vs EPA limit |
|---|---|---|---|
| Dry Town | Hayward | WI | 5300 µg/L 6625% of the EPA limit, in the worst sample — 80 µg/L |
| Choconut Creek Apartments | Binghamton | NY | 1700 µg/L 2125% of the EPA limit, in the worst sample — 80 µg/L |
| Coke County Wsc | Robert Lee | TX | 1387 µg/L 1734% of the EPA limit, in the worst sample — 80 µg/L |
| Colchester Estates | Colchester | NY | 1180 µg/L 1475% of the EPA limit, in the worst sample — 80 µg/L |
| Lakeshore Sites Water | Haskell | TX | 1114 µg/L 1393% of the EPA limit, in the worst sample — 80 µg/L |
| Rowena Wsc | Rowena | TX | 836 µg/L 1045% of the EPA limit, in the worst sample — 80 µg/L |
| Icmsa Cherrytree | Indiana | PA | 713 µg/L 891% of the EPA limit, in the worst sample — 80 µg/L |
| City of Robert Lee | Robert Lee | TX | 687 µg/L 859% of the EPA limit, in the worst sample — 80 µg/L |
| Choctaw Co. Rwsg & Swmd #6 | Boswell | OK | 650 µg/L 813% of the EPA limit, in the worst sample — 80 µg/L |
| City of Nome | Nome | TX | 645 µg/L 806% of the EPA limit, in the worst sample — 80 µg/L |
| Chefornak Water System | Chefornak | AK | 636 µg/L 795% of the EPA limit, in the worst sample — 80 µg/L |
| North Runnels Wsc | Winters | TX | 602 µg/L 753% of the EPA limit, in the worst sample — 80 µg/L |
| Wildwood Mhp Ws | West Monroe | LA | 598.7 µg/L 748% of the EPA limit, in the worst sample — 80 µg/L |
| Grove Mhp | Lutz | FL | 584.79 µg/L 731% of the EPA limit, in the worst sample — 80 µg/L |
| Hudson Gaars Mill Water System | Dodson | LA | 582.6 µg/L 728% of the EPA limit, in the worst sample — 80 µg/L |
| City of Ballinger | Ballinger | TX | 582 µg/L 728% of the EPA limit, in the worst sample — 80 µg/L |
| Wenden Dwid | Wenden | AZ | 580 µg/L 725% of the EPA limit, in the worst sample — 80 µg/L |
| Beverly Beach Water System | Beverly Beach | FL | 548.64 µg/L 686% of the EPA limit, in the worst sample — 80 µg/L |
| Village of Surfside Beach | Surfside Beach | TX | 544 µg/L 680% of the EPA limit, in the worst sample — 80 µg/L |
| Pleasant Hills-Crossroads Water Systems | Joyce | LA | 541 µg/L 676% of the EPA limit, in the worst sample — 80 µg/L |
| Osage Co Rwd #20 (Hulah) | Bartlesville | OK | 531 µg/L 664% of the EPA limit, in the worst sample — 80 µg/L |
| Buckland Water System | Buckland | AK | 525 µg/L 656% of the EPA limit, in the worst sample — 80 µg/L |
| J ; S Fish Camp | Okeechobee | FL | 523.37 µg/L 654% of the EPA limit, in the worst sample — 80 µg/L |
| East Columbia Water System | Columbia | LA | 523 µg/L 654% of the EPA limit, in the worst sample — 80 µg/L |
| Village of Calvin Water System | Calvin | LA | 520.6 µg/L 651% of the EPA limit, in the worst sample — 80 µg/L |
Frequently asked questions about TTHM
What is TTHM in drinking water?
Total trihalomethanes are by-products formed when chlorine reacts with organic matter; long-term exposure is linked to bladder cancer.
What is the EPA limit for TTHM?
The EPA's Maximum Contaminant Level for TTHM is 80 µg/L. A result above the limit means the supplier must act; the goal is the level at which no health effects are expected.
How common is TTHM in US tap water?
Of the 35,559 water suppliers with results on file, 30,898 detected TTHM — 86.9% of those tested.