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DIRECTORY: FAN > Health > Newsletter > Issue # 19

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FAN SCIENCE-WATCH
January 12, 2005

Issue #19: A review of recently published papers on fluoride

By Michael Connett

First, my apologies to Science-Watch bulletin readers for the length of time that has transpired since the last bulletin. I have been working on a new science-based database on fluoride/health effects that we hope to post on the FAN website in the not-too-distant-future. It should prove to be an exciting addition to the current array of information available on the FAN website.

During the time that has lapsed between the last bulletin and now, a number of important papers on fluoride have been published.

To start the new year off, I thought it would be useful to do a quick review of some of the more interesting papers published in the closing months of 2004, and the initial weeks of 2005.

Without further adieu, here they are...

Total Fluoride Exposure:

Erdal S, Buchanan SN. (2005). A quantitative look at fluorosis, fluoride exposure, and intake in children using a health risk assessment approach. Environmental Health Perspectives 113:111-7. Available online at: http://ehp.niehs.nih.gov/members/2004/7077/7077.html

This paper attempts an analysis of current fluoride exposure from all sources among US children in fluoridated and unfluoridated communities. The authors report a fact that is becoming increasingly obvious: that some children in both fluoridated AND unfluoridated areas are receiving more fluoride than the recommended daily amount.

To quote: “the findings of this health risk assessment study support concerns that a segment of the infant and child population in the United States may be exposed to amounts of fluoride greater than the optimum level for caries prevention... This raises questions about the continued need for fluoridation in the U.S. municipal water supply to protect against the risk of fluorosis.”

USDA (2004). USDA National Fluoride Database of Selected Beverages and Food. Nutrient Data Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, USDA. Available online at: http://www.nal.usda.gov/fnic/foodcomp/Data/Fluoride/fluoride.pdf

In October, the US Department of Agriculture released a database compiling the fluoride content of various foods and beverages sold in the U.S. While there are some limitations and problems with the database (e.g. no data on processed chicken infant foods, incorrect reporting of published data on fluoride content in grape juice, and lower fluoride values for soda than previously documented), it does contain quite a large amount of data and is worthy of becoming familiar with.

Fluoride/Brain:

Wang J, Ge Y, Ning H, Wang S. (2004). Effects of high fluoride and low iodine on biochemical indexes of the brain and learning-memory of offspring rats. Fluoride 37(3): 201-208.

Wang J, Ge Y, Ning H, Wang S. (2004). Effects of high fluoride and low iodine on oxidative stress and antioxidant defense of the brain in offspring rats. Fluoride 37(4): 264-270.

These two papers, from a research team in China, examine the interactive effects of high fluoride and low iodine on the brain of rats. They provide a valuable addition to the steadily growing literature on fluoride’s neurotoxicity. The papers report that both high fluoride by itself, and low iodine by itself, damages rat brain. Most interesting, however, is the fact that the damage to the brain was greatest when the elevated fluoride exposure was coupled with the iodine deficiency.

The findings from this team are particularly interesting in light of a recent UNICEF-sponsored study in China, where fluoride exposure in humans was found to exacerbate the IQ deficits induced by iodine deficiency, even at fluoride water levels as low as 0.88 ppm. See: http://www.fluoridealert.org/health/brain/idd.html

For a list of other recent studies on fluoride/brain, see:
http://www.fluoridealert.org/science-watch/12#studies

Fluoride/Miscellaneous:

Stone R. (2004). Iceland's Doomsday Scenario? Science 306:1278-1281.

This report, published in the November 19th issue of Science, examines the impact of a massive volcano eruption in Iceland back in 1783 - an event estimated to have killed about 10,000 Icelanders (20% of the population) and up to thousands more in Europe - and the possibility that another such eruption may once again occur. The article focuses in on research being conducted by a team led by Dr. Peter Baxter from the University of Cambridge in England. Baxter and colleagues have recently been exhuming the corpses of Icelanders who died in the months following the 1783 eruption, and analyzing their bones for fluoride content and for bone effects indicative of fluoride poisoning. As the article notes, Baxter and colleagues are “testing a thesis that fluoride in Laki’s emissions poisoned people directly and may account in part for the high death toll.”

The following are some excerpts from the article:

“During the eruption, an estimated 1 million tons of hydrofluoric acid were deposited over Iceland, contaminating the country’s food and drinking water supplies. Icelanders who lived through the eruption noted that sheep and other livestock developed knobbly protrusions from their bones that were clearly visible under the skin – a telltale sign of fluorosis. Baxter’s team is the first to exhume presumed victims of Laki to look for abnormal bone growth and high levels of fluoride that could well have led to fatal poisoning in people during the later months of the eruption... During the Laki eruption, ‘fluorine poisoning was observed all over Ireland’ in the form of bone malformations, says Thordarson. ‘We know the livestock were being poisoned and that within months people started dying,’ says Hildur. ‘But no one wondered whether people were also dying from direct poisoning’ from contaminated food or water... The heftiest doses would have come through drinking water, possibly up to 30 or 40 parts per million – as much as 30 times the permissible level today, says Baxter. ‘It was high enough that you would have felt sick if you drank the water,’ he says. ‘But they were in such a terrible state, they had no choice.’ The Icelanders were already suffering from deficiencies in vitamins C and D. ‘Then add fluorine,’ he says. ‘Nutrient deficiency could have made the population much more susceptible to fluoride poisoning.’... The Laki eruption has been a tragedy lost in time. ‘People ignored it for so long,’ says Thoradson. That’s changing. Volcanologists now view Laki as a potent warning, and some are considering what could be done to prepare for a reprise, beyond protecting food supplies and handing out respiratory masks... The deformed, fluoride-laden bones that Hildur and Baxter have unearthed may provide another powerful testament to the peril of taking Iceland’s fissures lightly.”

Sellers C. (2004). The artificial nature of fluoridated water: between nations, knowledge, and material flows. Osiris 19:182-200.

This paper makes a unique attempt to understand and juxtapose the differing scientific/popular views of fluoride in the US (where the emphasis has been on benefits) with the scientific/popular views of fluoride in India (where the emphasis has been on risks). While this paper could be improved and expanded upon in several ways, it has addressed in a scholarly manner an interesting aspect of the fluoride issue: namely, the divergence of how fluoride is perceived in different areas of the world – from a “nutrient” or drug that keeps teeth healthy, to a dangerous contaminant that wreaks havoc on health.

Fluoride/Kidney:

Karaoz E, et al. (2004). Effect of chronic fluorosis on lipid peroxidation and histology of kidney tissues in first- and second-generation rats. Biological Trace Element Research 102:199-208.

This study is the latest in a long line of animal studies finding that high fluoride exposure damages the kidney. What makes this study unique, however, is that the authors studied the impacts of fluoride over several generations of rats exposed to fluoride. Unfortunately, since I have only read the abstract (I have ordered the full study but haven’t yet received it), it’s difficult to determine how the multi-generational exposure impacted the results. However, based on the abstract from PubMed, it is clear that significant kidney damage was nonetheless found. To quote:

“Hydropic epithelial cell degenerations and moderate tubular dilatation were observed in some proximal and distal tubules. There were markedly focal mononuclear cell infiltrations and hemorrhage at some areas of the interstitium, especially at the corticomedullar junction. Mononuclear cell infiltrations were also evident in some peritubular and perivascular areas. Most of the vascular structures were congestive. Many Bowman capsules were narrowed. The severe degenerative changes in most of the shrunken glomerules and vascular congestion were also observed.”

Fluoride/Teeth:

Birkeland JM, et al. (2005). Severity of dental caries among 12-year-old Sudanese children with different fluoride exposure. Clinical Oral Investigations Jan 6; [Epub ahead of print]

This paper examined the impact of varying concentrations (0.4 ppm, 1.8 ppm, 2.9 ppm) of fluoride in drinking water on the tooth decay rates in children from Sudan. As with other recent studies from Africa, the authors failed to find a reduction in tooth decay as a function of fluoride exposure. To quote:

“The lack of a difference in caries prevalence between children in areas with 0.4 and 2.9 mg fluoride in the drinking water and a higher prevalence in a 1.8 mg area than in a low fluoride area was confirmed by multivariate analyses (Table 4). These findings confirm the lack of consistency of a cariostatic effect of fluoride in drinking water in African countries... Based on permanent molars indicated for extraction or missing because of caries, children in the 1.8 mg fluoride area had 3.7 times greater risk (odds ratio) of caries than children in the 0.4 mg area. The socio-economic conditions in the villages were presumed to be equal. However, the purchasing power in the 1.8 mg area furthest from Khartoum may have been greater than in the other areas. The 1.8 mg fluoride in the drinking water failed to control progression of caries. This study confirms the inconsistency of the cariostatic effect of fluoride in African countries.”

Al Dosari AM, et al. (2004). Caries prevalence and its relation to water fluoride levels among schoolchildren in Central Province of Saudi Arabia. International Dental Journal 54:424-8.

This study examined the impact of water fluoride exposure and caries rates in Saudi Arabia. As with the study noted above, it failed to find a linear correlation between fluoride exposure and tooth decay. To quote:

“Among the primary schoolchildren there was statistically significant (p < 0.05) difference in mean dmft scores at various fluoride levels with lowest dmft scores at the optimum water fluoride level (0.61-0.80ppm) and highest at two extremes i.e. 0.0 to 0.3ppm and > 2.5ppm, while in intermediate schoolchildren no significant difference in overall mean DMFT scores of children at various water fluoride levels could be found. CONCLUSION: The caries experience among the primary and intermediate schoolchildren in Riyadh and Qaseem was very high, and there was no linear correlation between water fluoride level and caries experience in these children.”

Khan AA, Whelton H, O'Mullane D. (2004). Is the fluoride level in drinking water a gold standard for the control of dental caries? International Dental Journal 54:256-60.

This study examined the impact of water fluoride exposure and caries in Pakistan. It observes that if there is an ‘optimal’ level of fluoride in water for Pakistan, it is well below 1 ppm. The authors estimate, based on their results, that the optimal concentration of fluoride for reducing tooth decay in Pakistan lies in the range of 0 to 0.33 ppm. The authors conclude that “There are no gold standards for setting up a universal optimal level of fluoride in drinking water and each country needs to determine the concentration of fluoride in their drinking water in accordance with its socio-economic and climatic conditions, dietary and oral hygiene habits of its population, and local research to determine how much fluoride is beneficial in the control of caries.”

Fluoride/Genetics:

Vieira AP, et al. (2004). Tooth Quality in Dental Fluorosis: Genetic and Environmental Factors. Calcified Tissue International Oct 14; [Epub ahead of print]

This paper brings some needed attention to the potential importance of genetics in determining an individual’s vulnerability to fluoride toxicity. While recent research on aluminum workers in Russia indicates that a genetic predisposition to fluorosis does in fact exist (Lavryashina 2003; Polzik 1994), there has been extremely little research on this aspect of fluoride toxicity here in North America. In this paper the authors report findings from a study on mice which suggest that genetic factors may play a role in determining the severity of dental fluorosis.