In fact, the study's authors say that more research needs to be done. This study was funded, in part, by EPA as part of the agency's data gathering efforts for a new rule which may lower the allowable level of TTHMs. The current Federal and State standard for TTHMs in drinking water is 100 micrograms per liter. This standard only applies to community systems serving a population of 10,000 or more. There is currently no standard for TTHMs for systems serving fewer than 10,000 people.
TTHM formation occurs when chlorine is added to water containing natural organic compounds.
Utah has relatively low levels of these organic compounds in its water sources and, in general, does not have a significant problem with TTHMs. The average TTHM level in samples taken during 1996 and 1997 was approximately 18 micrograms per liter. This is significantly below the TTHM level associated with increased risk of miscarriage. Additionally, as concerns about TTHMs have been raised, water system operators have endeavored to minimize their formation during the disinfection process. Furthermore, there is not much data available on TTHM levels in systems that serve fewer than 10,000 people.