Disinfection byproducts · 2025
TTHM in City of Poquoson, VA tap water
City of Poquoson, VA's 2025 report shows TTHM detected, but the EPA has not set an enforceable federal limit for it.
The measurement
| Statistic | Value | Federal limit |
|---|---|---|
Range Range of Individual Test Results Low | 6–32 ug/L | 0 ug/L MCLG |
Reported level System-wide | 21 ug/L | 0 ug/L MCLG |
Range System-wide | 4–40 ug/L | 0 ug/L MCLG |
Highest single sample Max Conc | 40 ug/L | 0 ug/L MCLG |
Maximum Max Conc | 21 ug/L | 0 ug/L MCLG |
Range System-wide | 4–40 ug/L | 80 ug/L MCL |
Maximum Max Detected Level | 40 ug/L | 80 ug/L MCL |
Range System-wide | 6–32 ug/L | 0 ug/L MCLG |
Verbatim from City of Poquoson, VA's 2025 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 City of Poquoson, VA 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 City of Poquoson, VA tap water?
Yes — City of Poquoson, VA's 2025 Consumer Confidence Report lists TTHM at 4–40 ug/L. City of Poquoson, VA's 2025 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 MCLG for TTHM is 0 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 2025 Consumer Confidence Report published by the City of Poquoson, VA 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/va/poquoson/2025/source.