In Parts 1 and 2 of this three-part series, we discussed a number of problems surrounding the use of water fluoridation, including questions about its effectiveness in reducing dental decay, the thin margin of safety that exists for fluoride and the exposure we face to fluoride from multiple sources. We also reviewed studies showing that water fluoridation and fluoride exposure are associated with disorders such as dental fluorosis, skeletal fluorosis, bone fractures and suboptimal thyroid functioning.
In this third and final installment, we discuss another potential problem posed by the fluoridation process -- accidents in treatment plants that can lead to fluoride poisoning. We also look at certain steps that can be taken to reduce the risk of a fluoride overdose, one city's rejection of the fluoridation process, and the difficulties involved in challenging such a long-used practice as water fluoridation, which has been supported by the US government and the American Dental Association for many decades.
Over the years, a number of fluoride accidents have occurred at water facilities. In some cases, excess fluoride has permeated the water supply and sickened or killed people. The Fluoride Action Network, which operates the Web site www.fluoridealert.org, has compiled information on a handful of fluoride accidents that occurred in recent years. (1) They include:
* June 2002 -- Dublin, California. Employees of a local business became sick when they drank over-fluoridated water. Samples of water from the business had fluoride concentrations of 250 ppm (the required level is 1 ppm to 2 ppm). The incident made 23 people sick, and the fluoride-pumping system was temporarily shut down pending an investigation. (2)
* February 2001 -- Fort Wayne, Indiana. About 6,000 gallons of hydrofluorosilicic acid, the substance used to add fluoride to public drinking water, spilled from the Three Rivers Water Filtration Plant into a sewer. Fumes from the acid caused headaches and respiratory problems in plant employees. Officials said the water supply was not threatened by the spill. (3)
* October 2000 -- Coos Bay, Oregon. A tank holding the highly acidic fluoride added to drinking water overflowed at a water treatment plant. Four hundred gallons of the chemical flowed into a floor drain and reached a nearby sewage treatment plant, where it killed off microorganisms used in the sewage treatment process. Some 3.5 million gallons of the partially treated sewage were then dumped into Coos Bay. (4)
* July 2000 -- Wakefield, Massachusetts. An overdose of fluoride was accidentally released into the water supply, bringing the levels of fluoride in the water to 23 milligrams per liter. The limit set by the state's Department of Environmental Protection is 4 mpl. (5)
In addition to these reports, the Townsend Letter for Doctors and Patients published a comprehensive summary of fluoride accidents between 1979 and 1993 in its October 1994 issue. (6) We list some of those incidents here:
* July 1993 -- Chicago, Illinois. Three dialysis patients died and five experienced toxic reactions to fluoridated water used in the treatment process. The CDC was asked...