A new study, to be published in the journal Environmental Research, adds further support to recent conclusions on fluoride toxicity by the National Academy of Sciences (NAS). The study, conducted by a team of researchers at Tongji Medical College in China, suggests that fluoride exposure – at levels currently deemed safe by the US Environmental Protection Agency (EPA) – can damage both kidney and liver function in children (1).
Earlier this year, an NAS panel concluded that EPA’s safe drinking water standard for fluoride – currently set at 4 ppm – “should be lowered” due to evidence linking fluoride exposure at this level to multiple adverse effects on human health (2).
A new study from China, meanwhile, has detected evidence of kidney and liver disturbances in children drinking water with as little as 2 ppm fluoride -– half the level of fluoride currently deemed safe by the EPA.
According to the authors, “our results suggest that drinking water fluoride levels over 2.0 mg/L (ppm) can cause damage to liver and kidney function in children…”
The authors arrived at this conclusion after studying a group of 210 children living in areas with varying levels of fluoride in water (from 0.61 to 5.69 ppm). Among this group, the children drinking water with more than 2 ppm fluoride – particularly those with dental fluorosis – were found to have increased levels of lactic dehydrogenase in their blood (an indicator of liver damage) and increased levels of NAG and y-GT in their urine (two markers of kidney damage).
While definitive conclusions about the risks of fluoride exposure to kidney and liver function can not be drawn from this single study, it bears noting that several animal studies have previously found evidence of fluoride-related kidney damage at levels as low as 1 ppm in rats, and 5 ppm in monkeys (3-6). Furthermore, the possibility that fluoride can damage the kidney is boosted by the fact that, of all soft tissues, the kidney is exposed to the highest levels of fluoride (with the possible exception of the pineal gland).
According, for instance, to the recent NAS report:
“Human kidneys… concentrate fluoride as much as 50-fold from plasma to urine. Portions of the renal system may therefore be at higher risk of fluoride toxicity than most soft tissues.”
Unfortunately, 60 years after water fluoridation began, there remains a scarcity of research investigating the effect of fluoridated water on kidney, or liver, function. As noted by the NAS, “Early water fluoridation studies did not carefully assess changes in renal function.”
This fact was not lost on the authors of the current study. As they note in the introduction:
“Surprisingly, few studies have examined the effects of fluoride on the functions of human liver and kidney and the possible dose–effect relationship between fluoride levels and damage to human liver and kidney functions.”
In fact, because of the scarcity of such research, the recent NAS report had actually specifically recommended that:
“The effect of low doses of fluoride on kidney and liver enzyme functions in humans needs to be carefully documented in communities exposed to different concentrations of fluoride in drinking water.”
1. Xiong X, Liu J, He W, Xia T, He P, Chen X, Yang K, Wang A. (2006). Dose-effect relationship between drinking water fluoride levels and damage to liver and kidney functions in children. Environmental Research Jul 8; [Epub ahead of print]
2. National Research Council. (2006). Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. National Academies Press, Washington D.C.
3. Varner JA, et al. (1998). Chronic administration of aluminum-fluoride and sodium-fluoride to rats in drinking water: Alterations in neuronal and cerebrovascular integrity. Brain Research 784: 284-298.
4. Manocha SL, et al. (1975). Cytochemical response of kidney, liver and nervous system to fluoride ions in drinking water.Histochemical Journal 7: 343-355.
5. Sullivan WD. (1969). The in vitro and in vivo effects of fluoride on succinic dehydrogenase activity. Fluoride 2:168-175.
6. Ramseyer WF, et al. (1957). Effect of sodium fluoride administration on body changes in old rats. Journal of Gerontology 12: 14-19.