Federal Fluoride Cap Too High
August 16, 2007

Federal Fluoride Cap Too High : Children are overexposed


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.