Disinfection byproducts · 2024
TTHM in Portland, OR tap water
Portland, OR's 2024 report shows TTHM detected, but the EPA has not set an enforceable federal limit for it.
The measurement
| Statistic | Value | Federal limit |
|---|---|---|
Reported level System-wide | 16.8–41 ug/L | None set |
Reported level System-wide | 20.3–32.1 ug/L | 80 ug/L MCL |
Verbatim from Portland, OR's 2024 Consumer Confidence Report — source document ↗
About TTHM
Total trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter.
Long-term exposure above the federal limit is linked to liver, kidney, and central-nervous-system effects and increased cancer risk.
How Portland, OR compares
5 of the 395 systems measuring TTHM on The Water Map have it at or above the federal limit:
Nearby systems also reporting TTHM:
People also ask
+Is there TTHM in Portland, OR tap water?
Yes — Portland, OR's 2024 Consumer Confidence Report lists TTHM at 16.8–41 ug/L. Portland, OR's 2024 report shows TTHM detected, but the EPA has not set an enforceable federal limit for it.
+What's the federal limit for TTHM in drinking water?
The federal MCL for TTHM is 80 ug/L. The EPA enforces this against the regulated reporting statistic (running annual average or 90th percentile), not a single-sample spike.
+What is TTHM?
Total trihalomethanes — a group of four chemicals (including chloroform) formed when chlorine reacts with natural organic matter. Long-term exposure above the federal limit is linked to liver, kidney, and central-nervous-system effects and increased cancer risk.
+Which other U.S. cities have TTHM over the federal limit?
5 of the 395 systems on The Water Map measuring TTHM report it at or above the federal limit. Examples include Albuquerque, NM, City of Hemet, CA, City of Menifee, CA.
+Where does this TTHM measurement come from?
This page reproduces the TTHM entry from the 2024 Consumer Confidence Report published by the Portland, OR water utility — the annual drinking-water report every U.S. utility is required by federal law to publish. The original source document is archived at /water/or/portland/2024/source.