Trihalomethanes (THMs)
Trihalomethanes (THMs) are disinfection byproducts created when chlorine is used to disinfect water containing natural organic matter.
Although some studies have indicated an association between elevated levels of THMs and adverse health effects among pregnant women, no causal relationship has been established.
The Environmental Protection Agency (EPA) maximum contaminant level of total THMs in treated water is 0.08 milligrams per liter. Southern Nevada's municipal water supply meets that health-based standard.
Several factors affect THM formation, including the amount of chlorine used during treatment, the concentration of total organic carbons in the source water, temperature, pH and retention time in the system.
The Southern Nevada Water Authority, which treats the valley's water supply, takes proactive measures to manage the formation of THMs during the water treatment process.
While science has not established a causal relationship between THMs and adverse health affects among pregnant women, the Water Authority advises consumers—particularly pregnant women—to call the EPA's Safe Drinking Water Hotline at (800) 426-4791 about any concerns related to THMs.