Disinfection byproducts · 2025
TTHM in James City County, VA tap water
James City County, VA's 2025 TTHM measurement is below the federal limit of 0 ug/L (MCLG).
The measurement
| Statistic | Value | Federal limit |
|---|---|---|
Range System-wide | 6–32 ug/L | 0 ug/L MCLG |
Maximum Max Detected Level | 40 ug/L | 80 ug/L MCL |
Highest single sample Max Conc | 40 ug/L | 0 ug/L MCLG |
Range System-wide | 4–40 ug/L | 80 ug/L MCL |
Range System-wide | 4–40 ug/L | 0 ug/L MCLG |
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 |
Maximum Max Conc | 21 ug/L | 0 ug/L MCLG |
Verbatim from James City County, 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 James City County, 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 James City County, VA tap water?
Yes — James City County, VA's 2025 Consumer Confidence Report lists TTHM at 40 ug/L. James City County, VA's 2025 TTHM measurement is below the federal limit of 0 ug/L (MCLG).
+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 James City County, 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/james-city-county/2025/source.