Fluoride is a naturally occurring element. Most sources of drinking water contain some naturally occurring fluoride. Dental experts indicate that fluoride helps teeth resist decay and therefore fluoride has been added to the drinking water supplies in many U.S. communities since 1945.

In 1995, the California legislature passed AB 733, which requires fluoridation of all water systems serving 10,000 customers or more, when funding is made available.

In November 2007, the Metropolitan Water District of Southern California (MWD) began adding fluoride to the drinking water it provides IRWD and other Southern California water agencies after being requested to do so by the health agencies in all counties it serves. MWD serves 18 million people from Ventura south to San Diego. Irvine Ranch Water District receives approximately 35% of its total water supply from MWD.

MWD adjusts the natural fluoride level, which ranges from 0.1 to 0.4 parts per million, to 0.7 to 0.8 parts per million, which is considered the optimal range for dental health. Fluoride levels in drinking water are limited under California state regulation to a maximum of 2.0 parts per million.

Naturally occurring fluoride levels in the groundwater from IRWD's Dyer Road Wellfield average 0.42 parts per million. Customers who receive a mixture of water from MWD and this groundwater receive water with an annual average fluoride concentration of approximately 0.6 parts per million, which is very close to the California Dept. of Public Health optimal range. Therefore, Irvine Ranch Water District currently has no plans to add fluoride to its well water.

Additional information is available at MWD's web site. Customers may also call the MWD Water Quality Information line at (800) 354-4420.

California Department of Public Health letter to health care professionals regarding fluoride supplements.