Federal Fluoride Cap Too High
Thursday, August 16, 2007

Federal Fluoride Cap Too High

Fluoride in Southern California Tap Water Will Put 64,000 Kids at Risk

In the four years since the Metropolitan Water District (MWD) decided to add fluoride to the tap water of millions of Californians, the American Dental Association (ADA), scientists at Harvard University, and the prestigious National Research Council (NRC) of the National Academy of Sciences have all raised serious concerns about the safety of fluoridated water for infants and young children. This steady stream of science represents a growing consensus within the mainstream public health and dental community that the health risks of fluoride in tap water may substantially outweigh the modest dental benefits of tap water fluoridation.

MWD should put its fluoridation plans on hold until all of the latest science has been evaluated and until the serious outstanding toxicity concerns with fluoride have been resolved.

One specific issue raised by both the NRC and the ADA is that infants and children under two years old may be overexposed to fluoride because they consume more water than adults relative to their size. A new analysis by Environmental Working Group (EWG) confirms these concerns.

EWG analyses show that if the Metropolitan Water District (MWD) of Southern California proceeds with plans to add 0.8 parts per million fluoride to its water beginning in October, more than 64,000 children will be exposed to fluoride at doses above what government agencies consider safe (0.1 milligrams of fluoride per kilogram of body weight per day, or 0.1 mg/kg/d). This maximum safe dose is consistent with the recommended fluoride exposure limits published by the National Academy of Sciences' (NAS's) Institute of Medicine and endorsed by the American Dental Association, and is also consistent with the maximum dose currently considered safe by the Environmental Protection Agency (EPA) (0.11 mg/kg/d). Last year the NAS's National Research Council found that this EPA maximum "safe" dose is too high to protect children, and "should be lowered." In light of the NRC recommendations, EWG's analysis likely underestimates the number of children in Southern California who would be exposed to fluoride at levels of concern.

MWD's plan to add fluoride to the water it supplies to 18 million customers in most of Los Angeles, Orange, San Diego, and parts of San Bernardino, Riverside and Ventura counties will put 14.5 percent of children under 1 year old, and 12.5 percent of children 1 to 2 years old, over the federal government's acceptable daily intake for fluoride (0.1 milligrams of fluoride per kilogram of body weight per day). In Los Angeles County alone, more than 40,000 children age 2 and under will exceed the safe dose.

 

MWD's fluoride plan will expose 64,000 children in 3 counties to unsafe doses

  Children under age 1 at risk Children age 1-2 at risk Total children age 2 and under at risk
Los Angeles County 21,516 18,549 40,065
Orange County 6,449 5,560 12,009
San Diego County 6,405 5,522 11,927
Total 34,370 29,631 64,001

Note: Additional children in 3 other counties that are served in part by MWD will also be overexposed (San Bernardino, Riverside, Ventura)

SOURCE: Environmental Working Group, based on Centers for Disease Control data and U.S. Census estimates for July 2006

 

EWG’s computer-assisted analysis used dietary and water consumption information from the National Health and Nutrition Examination Survey (NHANES) and tap water fluoride data from the Centers for Disease Control (CDC) to model total fluoride exposures from tap water, food and toothpaste for children age 2 and under nationwide, who were selected as the focus of this exposure analysis because they are sensitive to fluoride's potential impacts on growth and development, and they receive a higher dose of fluoride, pound per pound, than any other segment of the population.

The exposure models were then compared to the government's published maximum safe exposure (0.1 milligrams per kilogram of body weight per day)1. Finally, the models were adjusted to reflect the amount of fluoride MWD plans to add (about 0.8 parts per million, compared to typical levels nationwide of 1 part per million) and the number of children age 2 and under in the six Southern California counties, according to U.S. Census estimates of July 2006.

The result is a conservative estimate of the number of children who will exceed the safe dose, because MWD also serves parts of Riverside, San Bernardino and Ventura counties. Also, some of the 26 local water agencies served by MWD already add fluoride to water after they receive it from the district. Customers of those utilities may be exposed to even higher levels of fluoride after the MWD fluoridation.

 

1 The NAS's Institute of Medicine and the American Dental Association recommend or endorse a maximum safe daily fluoride dose of 0.1 milligrams per kilogram of body weight per day (0.1 mg/kg/d). EPA’s Maximum Contaminant Limit for fluoride in drinking water is 4 parts per million. For the average person in the population (an adult weighing 70 kilograms, or 154 pounds, with EPA's standard assumption of 2 liters of water consumed daily), this is equivalent to a fluoride dose of 0.11 mg/kg/d, and this level of exposure has been historically considered EPA's maximum safe dose for fluoride in water. For infants, EPA has established a reference dose (safe daily dose) of 0.06 mg/kg/day, but this value has never been used for regulation or standard setting.

 

New Science on Fluoride’s Risks

The value of fluoride-containing toothpaste to dental health is clear; fluoride is a potent chemical that on contact kills microbes on the teeth, reducing the incidence of cavities. But a substantial and growing body of peer-reviewed science strongly suggests that ingesting fluoride in tap water does not provide the same dental benefits, and may present serious health risks.

In fact, children who drink fluoridated water are at increased risk of developing fluorosis, a defect of the permanent teeth resulting in dark staining and, in severe cases, substantial corrosion of the enamel. The CDC says that about 30 percent of children who drink fluoridated water have some degree of fluorosis.

In November 2006, the American Dental Association acknowledged for the first time the health risks of fluoride, and issued an “Interim Guidance on Fluoride Intake for Infants and Young Children.” It said that in areas where fluoride is added to tap water, if a child is being fed liquid concentrate or powdered infant formula mixed with water, parents should consider using fluoride-free bottled water.

But far more serious health risks have been identified since 2003, when MWD made its decision to fluoridate. Since then concern about fluoridation has emerged as a mainstream public health debate.

  • A March 2006 report from the National Academy of Sciences/National Research Council (NAS/NRC) identified fluoride as a potent hormone disruptor that may affect normal thyroid function. Fluoride's potential to impair thyroid function is most clearly illustrated by the fact that until the 1970s, European doctors used fluoride as a thyroid-suppressing medication for patients with hyperthyroidism. Today, many people living in communities with fluoridated tap water are ingesting doses of fluoride that fall within the range of doses once used by doctors to reduce thyroid activity in hyperthyroid patients (NRC 2006).
  • The NAS/NRC report also cited concerns about the potential of fluoride to lower IQ, noting that the "consistency of study results appears significant enough to warrant additional research on the effects of fluoride on intelligence." That finding was echoed by a December 2006 study published in the prestigious peer-reviewed journal The Lancet that identified fluoride as an “emerging” neurotoxin (Grandjean & Landrigan 2006).
  • A 2006 peer-reviewed study by four Harvard scientists and doctors strongly supports concerns that fluoridated water is linked to osteosarcoma, an often fatal form of bone cancer, in boys. The Harvard study found a five-fold increase in bone cancer among teenage boys who drank fluoridated water from ages 6 through 8, compared to those drinking non-fluoridated water (Bassin et al 2006).

 

Fluoride and Bone Cancer

Osteosarcoma, while rare, is the third most common form of cancer in children. Osteosarcoma accounts for about 3 percent of all childhood cancers. The five-year mortality rate is around 50 percent, and nearly all survivors have limbs amputated, usually legs.

The overall weight of the evidence strongly supports the conclusion that exposure to fluoride in tap water during the mid-childhood growth spurt between ages 5 and 10 increases the incidence of osteosarcoma in boys ages 10 through 19. Fifty percent of ingested fluoride is deposited in bones, and fluoride stimulates bone growth in the growing ends of the bones where the osteosarcoma occurs. Fluoride is also a confirmed mutagenic agent in humans, which suggests that fluoride can cause genetic damage in bone cells where it is actively deposited, in this case precisely where the osteosarcoma arises.

Animal studies add further credence to the potential link between fluoride and bone cancer in males. Only two animal cancer bioassays have been conducted with fluoride; both show rare bone tumors, many of which were malignant, in male but not female test animals.

In the Harvard study, elevated bone cancer risks in boys were identified at fluoride levels that are commonly found in American water supplies, and equivalent to the level that would be added to southern California water by the MWD (0.8 ppm). For drinking water systems with fluoride levels far below EPA's limit in drinking water (4 ppm), and 30 to 99 percent of the amount recommended by the CDC (0.7 to 1.2 ppm), the study reports elevated risks for exposure from ages five through ten, with a five-fold risk of osteosarcoma for those exposed at age seven. At 100 percent or more of the recommended level (and still far below legal maximum levels), the risk for exposure at seven years old rises to 7.2-fold.

 

Recommendations

In August 2007, over 600 medical, dental, scientific, academic, public health and environmental professionals signed a petition to Congress urging a moratorium on fluoridation until hearings and additional research are conducted. Signers include Dr. Arvid Carlsson, winner of the 2000 Nobel Prize for Medicine, who said, "Fluoridation is against all principles of modern pharmacology. It's really obsolete." (FAN 2007.)

Public water supplies should be safe for all consumers, young and old alike. It is deeply troubling that children in Southern California, including bottle-fed infants, will be drinking fluoridated water in spite of the many serious health concerns identified by recent science. We believe the evidence is clear that fluoride exposure should be limited to toothpaste, where it provides the greatest dental benefit and presents the lowest overall health risk.

We call on MWD to reconsider its 2003 decision to add fluoride to its water supplies. If this unnecessary and irresponsible action goes forward, we urge the district to take aggressive and comprehensive steps to inform its 18 million customers of the risks. This information should be provided to every residential water customer in the district, as well as to the news media, health centers, pediatricians, hospitals, obstetricians' offices, dental clinics and water departments.

 

References

ADA (American Dental Association). 2006. Interim Guidance on Fluoride Intake for Infants and Young Children. Nov. 8, 2006. http://www.ada.org/prof/resources/positions/statements/fluoride_infants.asp

Bassin EB, Wypij D, Davis RB, Mittleman MA. 2006. Age-specific Fluoride Exposure in Drinking Water and Osteosarcoma (United States). Cancer Causes and Control, April 2006.

FAN (Fluoride Action Network). 2007. “End Fluoridation,” Say 600 Physicians, Dentists, Scientists, and Environmentalists. Fluoride Action Network press release, Aug. 9, 2007. http://www.fluorideaction.org/statement.press.release.html

Grandjean P, Landrigan P 2006. Developmental neurotoxicity of industrial chemicals. The Lancet, Nov. 8, 2006.

NRC (National Research Council). 2006. Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Washington, DC: The National Academies Press. [Available at http://www.nap.edu/catalog/11571.html]

 

Children are overexposed

Summary

EWG analyses show that if the Metropolitan Water District proceeds with plans to fluoridate tap water in October 2007, more than 64,000 children in 3 counties will be exposed to fluoride above the maximum safe levels developed by the National Academy of Sciences' Institute of Medicine, endorsed by the American Dental Association, and consistent with Environmental Protection Agency and California drinking water limits. This maximum safe exposure level has been the basis for the legal limit of fluoride in drinking water since 1986, but its adequacy is far from certain. It has been called into question by the NAS's National Research Council; at least 4 government assessments have determined that a lower exposure limit is needed to protect children from tooth and bone damage; and a number of studies have since identified potential health risks not considered by EPA or California in setting drinking water standards. Because of the recognized limitations in current legal exposure limits, EWG's analyses (which rely on these limits) likely underestimate the number of children who will be at potential risk if MWD proceeds with its fluoridation plans.

Current fluoride limits may not protect children

At least four government assessments find "safe" exposure limits for fluoride to be lower than the doses associated with current drinking water limits (NRC 2006), outlined below. The assessments outlined below consider only bone and tooth damage, and not the full range of additional, emerging health concerns associated with fluoride. MWD's fluoridation plan would result in children exceeding all of these doses.

0.1 mg/kg/d (current drinking water standard)

This dose is the "tolerable upper intake" for ages 0-8 developed by the Institute of Medicine and endorsed by the American Dental aSsociation (IOM 1997; ADA 2005). It is consistent with EPA's legal limit in tap water, the Maximum Contaminant Level (4 ppm in water, equivalent to 0.11 mg/kg/d for 70 kg adult drinking 2 L water daily, per 40CFR 141.62(b)[2001]). This dose is 100 times higher than the recommended "adequate intake" for infants established by the Institute of Medicine (0.0014 mg/kg/d) (IOM 1997; ADA 2005).

0.1 mg/kg/d

This children's dose corresponds to the legal limit for fluoride in drinking water in the state of California of 2 ppm, half of the federal (EPA) standard. Although this is essentially the same dose represented by EPA's federal drinking water standard, California converts the dose to a drinking water concentration that would protect children from dental fluorosis, using a child's typical body weight and ingestion rates; in contrast, EPA set the federal standard to protect adults only, not children. (EPA also set a standard to protect children of 2 ppm, equal to California's enforceable limit, but this is a non-enforceable "Secondary Maximum Contaminant Level.")

0.083-0.13 mg/kg/d

The National Research Council found this dose to be the upper end of a safe and adequate daily dietary intake for children 1-10 years old (NRC 1989b).

0.06 mg/kg/d

The EPA established this "reference dose" as the limit for protecting children from objectionable enamel fluorosis (EPA 1989).

0.05 mg/kg/d

This dose is set by Agency for Toxic Substances and Disease Registry (ATSDR) as the minimal risk level, to protect from increased rates of bone fractures from chronic fluoride exposures (ATSDR 2003).

0.038-0.069 mg/kg/d

The National Research Council found this dose to be the upper end of a safe and adequate daily dietary intake for adults and children over 10 years of age (NRC 1989b).

NAS/NRC Conclusion

Though it did not recommend a maximum safe daily fluoride dose, in its comprehensive 2006 scientific review, the National Academy of Sciences' National Research Council found that EPA's drinking water exposure limit, based on a dose of approximately 0.1 mg/kg/d, does not adequately protect children and "should be lowered" (NRC 2006).

The surprising science behind fluoride drinking water standards

The science and policies used to develop fluoride drinking water limits in 1986 are inconsistent with current practice used to set public health standards. Typically, agencies consider the full range of potential health impacts including the most recent science; apply safety factors that normally range from 100 to 300 to account for differences in test or study conditions and variabilities in the real world; and set standards specifically to protect children and other vulnerable populations. In the case of fluoride, none of these standard procedures was followed. EPA derived the current federal drinking water standard from a 1937 worker study of crippling skeletal fluorosis (Roholm 1937), setting the 4 ppm drinking water limit as the equivalent dose to the 20 parts per million of fluoride in air to which these workers were exposed, adjusted by a safety factor of just 2.5. In setting the standard EPA ignored a published correction to Roholm (1937) showing that the harmful dose was half of what they had originally published. EPA has not updated its drinking water limit in the 21 years since its promulgation, even though a wealth of new science and assessments show it may not protect children. Their current, official "reference dose" to protect infants from permanent teeth mottling is 40 percent lower than than the dose associated with the current drinking water standard (0.06 mg/kg/d versus approximately 0.1 mg/kg/d). Even EPA advises the public that their current fluoride standard of 4 ppm is twice what poses risks during childhood for permanent teeth mottling (dental fluorosis): "children under nine should not drink water that has more than 2 mg/L of fluoride" (EPA 2007). The State of California chose to enforce the lower standard, 2 mg/L, to protect children from teeth mottling, but still, like EPA, has not updated their standard to reflect the growing body of literature linking fluoride to other health effects. MWD plans to add fluoride to Southern California water at 0.8 ppm, a level below both the federal and the California limit for fluoride in drinking water. But the toxicity of a chemical to an individual is driven not by the absolute level in water, but by the dose each person receives, which depends on their size and how much they drink. As noted above, both the federal and state drinking water standards were derived from a dose of about 0.1 milligrams of fluoride per kilogram of body weight per day. The allowable limits in water were calculated by assuming a typical body weight and water consumption rate. But in the real world, children (and adults) come in all sizes and drink widely varying amounts of water. Therefore, even though MWD will meet the drinking water standard derived from the "safe" dose, we find that when we consider government data on the real-world ranges of body weights and water consumption, many thousands of children in Southern California would be exposed to fluoride above the government's safe dose. Even though the fluoride concentrations in MWD will meet the state's standards, more than 64,000 children will be at potential risk. Remarkably, EPA’s pesticide program recently established an acceptable daily fluoride intake of 1.14 mg/kg/d, 10 times higher than the dose used for to develop the drinking water standard. In deriving this number, the Agency multiplied by 10 the acceptable daily dose for drinking water exposures. While there is no valid scientific rationale or precedent for this, the decision to use an assumed safe dose 10 times higher than the drinking water standard has allowed the Agency to approve fluoride-based pesticides for use in food, including the newly approved sulfonyl fluoride. Our analyses of the number of children in Southern California who will be exposed to fluoride above a safe dose if MWD proceeds with fluoridation plans, do not consider the additional fluoride exposures children face from fluoride-based pesticides in food; comprehensive government data are not yet available on levels of these pesticides in the food supply.

Fluoride health risks extend beyond teeth and bones

When the National Research Council reviewed the adequacy of current federal fluoride exposure limits, the committee unanimously agreed that the 4 ppm drinking water standard does not protect children from severe dental fluorosis, a dark staining, pitting and sometimes dramatic enamel loss of the teeth. According to the committee report, about 10 percent of children exposed to fluoride at this level will experience severe dental fluorosis (NRC 2006, pg 3). In addition, nine of 12 members of the committee concluded that long-term exposure to fluoride at 4 ppm will increase bone fracture rates in the population. But the committee also expressed concerns about other health effects associated with fluoride, including neurotoxic effects and neurobehavioral deficits, possible carcinogenicity, and thyroid, immune and endocrine effects. They drew no conclusion regarding the risk of these outcomes at current exposure levels and drinking water limits. If the MWD proceeds with plans to fluoridate Southern California tap water in October 2007, they will do so without full consideration of the potential risks this action might pose for the broad range of potential impacts now associated with fluoride.

 

 

Methodology: 

Summary

EWG developed estimates of the distribution of fluoride exposures for children under 2 years of age, considering aggregate exposures from food, incidental toothpaste ingestion, and fluoridated drinking water, including water used to reconstitute powdered or concentrated infant formula.

In our analysis we relied on data from the Centers for Disease Control and Prevention (CDC) National Health and Nutrition Exposure Survey (NHANES) to represent the distribution of food and water intake and body weight; and we incorporated estimates of toothpaste ingestion and fluoride levels in food from the open scientific literature.

From the distribution of fluoride exposure we developed using these parameters, we calculated the proportion of children under age 2 predicted to be exposed to fluoride in excess of the federal government's maximum safe dose of 0.1 mg/kg/day. This dose is consistent with 0.1 mg/kg tolerable upper intake level established by the Institute of Medicine of the National Academy of Sciences (NAS) and endorsed by the American Dental Association, and with the allowable daily dose established for drinking water by EPA (0.11 mg/kg/d).

Data sources

Our exposure model relies on data for 672 children under the age of 2 from the CDC's 2001-2002 National Health and Nutrition Examination Survey (NHANES). The data includes the distribution of body weight, types of food eaten and amounts consumed, drinking water consumption, and water content for reconstituted infant formula (http://www.cdc.gov/nchs/about/major/nhanes/nhanes01-02.htm). We compiled data on fluoride levels in food from the scientific published literature (USDA 2005, Buzalaf et al. 2004, Fein and Cerklewski 2001, Heilman et al. 1997, Jiménez-Farfán et al. 2004, Pang et al. 1992, Warnakulasuriya et al. 2002). We used data on toothbrushing frequency from the Iowa Fluoride Study (IFS), generously provided by the director of the IFS, Dr Steven Levy. We compiled data on toothpaste ingestion as a function of a child's age from a range of peer-reviewed sources (Naccache et al. 1992; Simard et al. 1989; Baxter 1980).

Analysis

We estimated the distribution of fluoride exposure for children under 2 years of age by modeling exposures for the range of individual children represented in the underlying data, with each "child" in our exposure model defined by a body weight, age, and daily food and water consumption pattern (food types and quantities consumed) detailed in the government survey called NHANES. For each child we matched the reported foods consumed to fluoride concentrations in those foods as detailed in the scientific literature. For all ages, the NHANES data report 4268 different foods consumed; for 548 of these EWG found fluoride contamination data in the scientific literature. These foods constitute 75 percent by weight of food consumed for by children under 2 years of age. In calculating fluoride exposures from water, we assumed that the water consumed by each child would contain fluoride at a concentration of 0.8 parts per million, consistent with the Metropolitan Water District's fluoridation plan. We determined fluoride exposure from tooth brushing by combining the mean toothpaste ingestion rate by age for each brushing, with data on how often children brush. The concentration of fluoride ion in the toothpaste was assumed to be 1000 mg/kg (CDC 2001). We assumed a brushing frequency for each modeled child by constructing a distribution of tooth-brushing frequency by age from the IFS data, where the data are categorized as 0, <1, 1, 2, or 3 times/day. Each child in the model was randomly matched with a frequency from this data set. For those who fell within the <1 times brushing/day category, half were assumed not to brush, and half were assumed to brush once a day. To calculate children's total fluoride exposure, we added fluoride exposures from tooth brushing to water and food exposures calculated for each individual in the NHANES survey as described above, and then divided this sum by the individuals’ recorded weight in the NHANES database to derive a total daily fluoride exposure in units of milligrams (mg) of fluoride per kilogram (kg) of body weight per day (d), or mg/kg/d. We ran the model in Monte Carlo fashion until results stabilized. We produced final model results by averaging results from successive model simulations, each of which randomly matched modeled children to tooth brushing frequencies in the IFS distribution. Final model results represent the average summary statistics for each age including the mean; 10-99th percentiles of mg/kg/day; percent contributions from water, food, and tooth-brushing; and percent of individuals over the EPA acceptable dose and IOM/ADA level.

Limitations

Our analysis likely underestimates children's fluoride exposures. Our estimates do not include fluoride exposures from the 25% of food consumed for which we found no fluoride testing data in the scientific literature. We do not include exposures to residues of the pesticide sulfuryl fluoride on food. This fluoride-based fumigant was recently approved for use on food by EPA, but data are not yet available on the levels at which it now contaminates the food supply. We also did not include exposures to fluoride supplements. Although CDC and ADA recommend that children in areas with fluoridated water not take supplements, many dentists disregard this advice (Levy and Carrell 1987).

References: 

ADA (American Dental Association). 2006. Interim Guidance on Fluoride Intake for Infants and Young Children. Nov. 8, 2006. http://www.ada.org/prof/resources/positions/statements/fluoride_infants.asp

ATSDR (Agency for Toxic Substances and Disease Registry). 2003. Toxicological pofile for fluorides, hydrogen fluoride, and fluorine. U.S. Department of Health and Human Services, Public Health Service, Atlanta, GA. September 2003.

Bassin EB, Wypij D, Davis RB, Mittleman MA. 2006. Age-specific Fluoride Exposure in Drinking Water and Osteosarcoma (United States). Cancer Causes and Control, April 2006.

Baxter PM. 1980. Toothpaste ingestion during toothbrushing by school children. Br Dent J. 1980 Mar 4;148(5):125-8.

Buzalaf MA, de Almeida BS, Cardoso VE, Olympio KP, Furlani Tde A.

Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil. Food Addit Contam. 2004 Mar;21(3):210-5.

EPA (U.S. Environmental Protection Agency). 2007. EPA Office of Water. Ground Water and Drinking Water. Drinking Water Contaminants. http://www.epa.gov/safewater/hfacts.html.

EPA (U.S. Environmental Protection Agency). 1989. Fluorine (Soluble Fluoride (CASRN 7782-41-4). Integrated Risk Information System. Available: http://www.epa.gov/iris/subst/0053.htm.

FAN (Fluoride Action Network). 2007. “End Fluoridation,” Say 600 Physicians, Dentists, Scientists, and Environmentalists. Fluoride Action Network press release, Aug. 9, 2007. http://www.fluorideaction.org/statement.press.release.html

Fein NJ, Cerklewski FL. 2001. Fluoride content of foods made with mechanically separated chicken. J Agric Food Chem. 2001 Sep;49(9):4284-6.

Grandjean P, Landrigan P 2006. Developmental neurotoxicity of industrial chemicals. The Lancet, Nov. 8, 2006.

Heilman JR, Kiritsy MC, Levy SM, Wefel JS. 1997. Fluoride concentrations of infant foods. J Am Dent Assoc. 1997 Jul;128(7):857-63.

IOM (Institute of Medicine). 1997. Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington, DC: National Academy Press.

Jimenez-Farfan MD, Hernandez-Guerrero JC, Loyola-Rodriguez JP, Ledesma-Montes C. 2004. Fluoride content in bottled waters, juices and carbonated soft drinks in Mexico City, Mexico. Int J Paediatr Dent. 2004 Jul;14(4):260-6.

Levy SM, Carrell AF. 1987. Compliance by health care providers with recommended systemic fluoride supplementation protocol. Clin. Prev. Dent. 9:19-22

Naccache H, Simard PL, Trahan L, Brodeur JM, Demers M, Lachapelle D, Bernard PM. Factors affecting the ingestion of fluoride dentifrice by children. J Public Health Dent. 1992 Summer;52(4):222-6.

NRC (National Research Council). 2006. Fluoride in Drinking Water: A Scientific Review of EPA’s Standards. Washington, DC: The National Academies Press. [Available at http://www.nap.edu/catalog/11571.html]

NRC (National Research Council). 1989. Recommended dietary allowances. 10th Ed. Washington, DC. National Academy Press.

Pang DT, Phillips CL, Bawden JW. 1992. Fluoride intake from beverage consumption in a sample of North Carolina children. J Dent Res. 1992 Jul;71(7):1382-8.

Roholm K. 1937. Fluoride intoxication: a clinical-hygienic study with a review of the literature and some experimental investigations. London: H.K. Lewis Ltd. Cited in Hodge HC. (1963). Safety factors in water fluoridation based on the toxicology of fluorides. Proceedings of the Nutrition Society 22: 111-117. (see http://fluoridealert.org/health/bone/fluorosis/intake/dose.html)

Simard PL, Lachapelle D, Trahan L, Naccache H, Demers M, Brodeur JM. 1989. The ingestion of fluoride dentifrice by young children. ASDC J Dent Child. 1989 May-Jun;56(3):177-81.

USDA (United States Department of Agriculture). 2005. USDA National Fluoride Database of Selected Beverages and Foods, Release 2. Nutrient Data Laboratory, Agricultural Research Service. Published December 2005.

Warnakulasuriya S, Harris C, Gelbier S, Keating J, Peters T. 2002. Fluoride content of alcoholic beverages. Clin Chim Acta. 2002 Jun;320(1-2):1-4.

Wolff WA, Kerr EG. 1938. Composition of human bone in chronic fluorine poisoning. Am. J. Med. Sci., 195: 493.