Can water fluoridation increase the levels of lead circulating in a child’s blood? This is the question that has been asked ever since Dartmouth scientist, Dr Roger Masters, and chemical engineer, Myron Coplan, published studies in 1999 and 2000 reporting that exposure to fluoridated water was associated with increased blood lead levels in children surveyed from Massachusetts and New York State. According to Masters and Coplan, this association was not observed for all fluoride chemicals, but only those water supplies treated with “silicofluorides” (e.g. fluorosilicic acid and sodium silicofluoride). In 2006 and 2007, three studies were published that added further evidence to the silicofluoride/lead link.
Prompted by Masters’ & Coplan’s research, a team of scientists from the University of Maryland and Centers for Disease Control (CDC) examined the blood lead levels of children from a recent national survey (NHANES) to assess if there was any association with water fluoridation (8). In January 2006, the authors published the results in Environmental Health Perspectives. While their findings did not neatly agree with Master’s and Coplan’s earlier studies, the authors did find that water fluoridated with hydrofluorosilicic acid was significantly associated with higher blood lead levels in children living in houses built prior to 1946. Although the authors downplayed this result, it was by no means trivial.
In 2007, Coplan published an analysis of the same NHANES data upon which the Macek study was based. Coplan’s analysis, which was published in the journal Neurotoxicology, found that children drinking water with silicofluorides had a significantly elevated risk of exceeding the hazard threshold for lead in blood (5 ug/dL). Although the risk was not as great as previously estimated, Coplan found that silicofluorides increased the lead risk in about 2 of every 100 children exposed — a notable difference considering that over 100 million Americans consume “silicofluoridated” water.
A team of researchers from the University of North Carolina-Ashville tested the silicofluoride/lead hypothesis by conducting a tightly controlled laboratory experiment. For the experiment, the authors submerged lead-containing brass pipes in water with various water treatment chemicals, including silicofluorides. The results of the study, which were published in Neurotoxicology, showed that silicofluorides increased lead erosion from the piping, particularly when added in conjunction with chloramines (a disinfectant commonly used as an alternative to chlorine). According to the authors:
“Prior to the present study, no one had looked at brass corrosion by combinations of either chlorine or chloramine with water fluoridating agents. Several factors applicable to such combinations can produce more corrosion than either of the disinfectants or fluoridating agents alone.”
One caveat to this laboratory study, however, is that the researchers added silicofluorides at a concentration of 2 ppm, which is slightly higher than the levels commonly added to drinking water (0.7-1.2 ppm).
Coplan MJ, et al. (2007). Confirmation of and explanations for elevated blood lead and other disorders in children exposed to water disinfection and fluoridation chemicals. Neurotoxicology 28(5):1032-42.
Macek M, et al. (2006). Blood lead concentrations in children and method of water fluoridation in the United States, 1988-1994. Environmental Health Perspectives 114:130-134.
Maas RP, et al. (2007). Effects of fluoridation and disinfection agent combinations on lead leaching from leaded-brass parts. Neurotoxicology 28(5):1023-31.