Fluoride increases lead concentrations in whole blood and in calcified tissues from lead-exposed rats

Sawan RM, Leite GA, Saraiva MC, Barbosa F Jr, Tanus-Santos JE, Gerlach RF. Toxicology. 2010 Apr 30;271(1-2):21-6. Epub 2010 Feb 25. (See study)


Higher blood lead (BPb) levels have been reported in children living in communities that receive fluoride-treated water. Here, we examined whether fluoride co-administered with lead increases BPb [blood lead] and lead concentrations in calcified tissues in Wistar rats exposed to this metal from the beginning of gestation. We exposed female rats and their offspring to control water (Control Group), 100mg/L of fluoride (F Group), 30mg/L of lead (Pb Group), or 100mg/L of fluoride and 30mg/L of lead (F+Pb Group) from 1 week prior to mating until offspring was 81 days old. Blood and calcified tissues (enamel, dentine, and bone) were harvested at day 81 for lead and fluoride analyses. Higher BPb concentrations were found in the F+Pb Group compared with the Pb Group (76.7+/-11.0microg/dL vs. 22.6+/-8.5microg/dL, respectively; p<0.001). Two- to threefold higher lead concentrations were found in the calcified tissues in the F+Pb Group compared with the Pb Group (all p<0.001). Fluoride concentrations were similar in the F and in the F+Pb Groups.

These findings show that fluoride consistently increases BPb and calcified tissues Pb concentrations in animals exposed to low levels of lead and suggest that a biological effect not yet recognized may underlie the epidemiological association between increased BPb lead levels in children living in water-fluoridated communities.


“This study shows that co-exposure to fluoride and lead from the beginning of gestation consistently increases the concentrations of lead in whole blood and in calcified tissues of 81-day-old animals, with no changes in the concentrations of fluoride. Lead concentrations were found to be 2.5 times higher in the superficial enamel, 3 times higher in surface bone, 2 times higher in whole bone, and 1.7 times higher in the dentine when the animals were co-exposed to fluoride, thus indicating a consistent rise in the amounts of lead found in whole blood and calcified tissues in the F + Pb Group. This is the first study to show that fluoride affects lead concentrations during lead exposure, and our findings may have serious implications for populations exposed to increased amounts of both lead and fluoride, particularly young children.

“Decreased learning ability and low hippocampus glutamate has been recently shown in offspring rats exposed to fluoride and lead.”

“…we speculate that the unknown mechanism that explains the increased lead levels found in the blood and in the calcified tissues may involve the effect of fluoride on the control of lead absorption in the intestine or excretion in the kidney.”


“In conclusion, this study showed that co-exposure to fluoride increases lead concentrations in the blood and in calcified tissues in animals exposed to lead from the beginning of gestation. These findings suggest that a biological effect not recognized so far may underlie the epidemiological association between increased BPb levels in children and water fluoridation.”

Commentary and emphasis:

Significantly, the fluoride source used in this study was hydrofluorosilicic acid (H2SiF6), one of the three chemicals used in water fluoridation. Prior to this study, hydrofluorosilicic acid had never been subject to toxicological testing; pharmaceutical grade sodium fluoride had been used instead.

Probably anticipating the usual criticism levelled against animal studies of this type by fluoridation proponents, the authors carefully address the issue of the concentrations of both lead and fluoride used in this experiment. They write:

“The concentration of lead in drinking water used in the present study is considered a low concentration for rodents. However, while the fluoride concentration used in the present study could be considered relatively high for rodents (100mg/L or ppm), this concentration was chosen because it produces plasma fluoride levels that are comparable with those commonly found in humans chronically exposed to 8mg/L of fluoride in the drinking water, which is a concentration known to cause severe fluorosis.

“Since this study was based on a hypothesis derived from epidemiological evidence from thousands of children (that fluoride from the water might increase BPb levels), we felt that we had to maximize fluoride concentrations to observe its influence on lead levels in this proof-of-concept animal study.

“Although children are not chronically exposed to high concentrations of fluoride (100ppm) by means of drinking/cooking water, children are frequently exposed to high levels of fluoride during their first years because of the many sources of fluoride available to them. Since fluoride is not considered a toxic agent, it is widely available through mouth rinses, toothpastes, tablets, besides the fluoride present in drinking water, beverages, and food… Therefore, it is likely that young children may experience episodes of exposure to high levels of fluoride, which may cause their BPb levels to increase and produce more lead toxicity.”

Special concerns for young children

“A reason for major concern is the fact that exposure to increased amounts of lead and fluoride occurs at about the same age (1-3 years). Some studies of fluorosis prevalence point to a higher degree of fluorosis in front teeth and first molars, which is an indirect measure of dose that indicates that the children receive the highest fluoride doses when their front teeth and first molars mineralize (at ages 1-5 years). This is about the same time when BPb levels are the highest in children. In fact, the exposure of children to lead apparently peaks at 12-36 months of age, which is the time when toddlers experience prominent hand-to-mouth behavior.

“Therefore, this is a critical time when systemic exposure to fluoride should be minimized, since fluoride may increase lead accumulation, and any preventable exposure to lead should be avoided.”

Fluoride Action Network (USA) comments:

In essence these authors have provided a well-designed animal study supporting the epidemiological findings of Masters and Coplan.

No one can deny that even very low levels of lead exposure can compromise the intellectual development and behavior of young children. If, as this experiment shows in animals, and Masters and Coplan may have found in epidemiological studies, that lead exposure (from any source) is increased by the presence of fluoride in the water, in any rational world this should force the end of fluoridation immediately. What parent in their right mind would knowingly allow the possibility that their child’s mental development  be impaired in exchange for some slight and questionable benefit to their teeth. However, without the mainstream media and the majority of environmental organizations involved in this issue it is hard to get this information to parents. Thus the chances are that this study will be ignored, like the landmark NRC (2006) review, by those governments determined to continue fluoridation whatever the costs to public health.

As each new scientific study makes the practice of water fluoridation more and more unjustified one feels as if one is caught up in some Kafka novel. We are trapped by a text that was written in 1950 when the US Public Health Service endorsed fluoridation with practically no science on the table. This endorsement set off such a cascade of endorsement dominoes from “professional” bodies that no one seems to have the guts to say was a terrible mistake. All one’s efforts to point out – like the little boy in Hans Christian Anderson’s famous tale – that the emperor has no clothes are met by derision by the modern day courtiers at the CDC and the ADA. Science has been subordinated to authority and public policy has become the plaything of the arrogant.

Meanwhile, for those who care for their common man this study is another critically important piece of ammunition in the battle to end this sordid practice worldwide.

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