Trihalomethanes (THMs)
Trihalomethanes (THMs) are disinfection byproducts created when chlorine is used to disinfect water containing natural organic matter.

Although THMs have been associated with adverse health effects among pregnant women, no causal relationship has been established.

The Environmental Protection Agency (EPA) has set the limit of total THMs in treated water at 0.080 milligrams/liter. Our treated water supply is well within that health-based standard.

The Southern Nevada Water Authority encourages the EPA to continue health effects research so it can provide water agencies the information necessary to minimize health risks associated with THMs.

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 distribution system.

The Southern Nevada Water Authority 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 SNWA advises consumers—particularly pregnant women—to call the EPA's Safe Drinking Water Hotline at (800) 426-4791 about any concerns related to THMs.