Total Trihalomethanes (TTHMs) in Drinking Water
EPA limits, health effects, and what to do if your water is affected.
🩨 Health Effects
TTHMs form when chlorine reacts with naturally occurring organic matter in water. Long-term exposure is linked to increased risk of bladder cancer, and some studies associate high levels with reproductive problems and miscarriage risk.
📍 Sources in Water
TTHMs are not found in nature; they are created during the water treatment process. Levels are higher in surface water systems and in summer months when organic matter and water temperatures are highest.
✅ What To Do
Activated carbon filters (NSF/ANSI 53 certified) and reverse osmosis reduce TTHMs. Refrigerating water in an open pitcher can also help dissipate them. Boiling water does not remove TTHMs and may concentrate them.
Check your tap water for Total Trihalomethanes (TTHMs)
Search your ZIP code to see if your water system has had Total Trihalomethanes (TTHMs) violations, plus lead testing results and an overall safety grade.
Search your ZIP code →Data from the EPA's Safe Drinking Water Information System (SDWIS). MCLs reflect minimum federal standards; some contaminants may pose health risks below these thresholds.