The rationale of the EPA’s Office of Water for not performing a six-year-review of fluoride in drinking water:
potential revision of the fluoride NPDWR is a lower priority that would divert significant resources from the higher priority candidates for revision that the Agency has identified, as well as other high priority work within the drinking water office.
The following is an excerpt from this Federal Notice:
2. Fluoride
Background
Fluoride can occur naturally in drinking water as a result of the geological composition of soils and bedrock. Some areas of the country have high levels of naturally occurring fluoride. EPA established the current NPDWR to reduce the public health risk associated with exposure to high levels of naturally occurring fluoride in drinking water sources.
Low levels of fluoride are frequently added to drinking water systems as a public health protection measure for reducing the incidence of cavities. The decision to fluoridate a community water supply is made by the state or local municipality, and is not mandated by EPA or any other federal entity. The U.S. Public Health Service (PHS) recommendation for community water fluoridation is 0.7 mg/L (U.S. Department of Health and Human Services, 2015). Fluoride is also added to various consumer products (such as toothpaste and mouthwash) because of its beneficial effects at low level exposures.
EPA published the current NPDWR on April 2, 1986 (51 FR 11396, USEPA, 1986) to reduce the public health risk associated with exposure to high levels of naturally occurring fluoride in drinking water sources. The current NPDWR established an MCLG and MCL of 4.0 mg/L to protect against the most severe stage of skeletal fluorosis (referred to as the “crippling” stage) (NRC, 2006a). EPA also established a secondary maximum contaminant level (SMCL) for fluoride of 2.0 mg/L to protect against moderate and severe dental fluorosis, which was considered at the time to be a cosmetic effect. As provided under the statute, the SMCL is not enforceable in the same manner as the MCL. Public notification is required when PWSs exceed the MCL or SMCL.
EPA has reviewed the NPDWR for fluoride in previous Six-Year Review cycles. As a result of the first Six-Year Review (68 FR 42908, USEPA, 2003b), EPA requested that the National Research Council (NRC) of the National Academies of Sciences (NAS) conduct a review of the health and exposure data on orally ingested fluoride. In 2006, the NRC published the results of its review and concluded that severe dental fluorosis is an adverse health effect when it causes both a thinning and pitting of the enamel, a situation that compromises the function of the enamel in protecting against decay and infection (NRC, 2006a). The NRC recommended that EPA develop a dose-response assessment for severe dental fluorosis as the critical effect and update an assessment of fluoride exposure from all sources.
During the Six-Year Review 2, the Agency was in the process of developing a dose-response assessment of the non-cancer impacts of fluoride on severe dental fluorosis and the skeletal system. In addition, EPA was in the process of updating its evaluation of the relative source contribution (RSC) of drinking water to total fluoride exposure considering the contributions from dental products, foods, pesticide residues, and other sources such as ambient air and medications. These assessments were not completed at the time of the Six-Year Review 2; thus, no action was taken under the Six-Year Review 2 (75 FR 15500, USEPA, 2010h).
In 2010, EPA published fluoride health assessments. The “Dose Response Analysis for Non-Cancer Effects” (USEPA, 2010b) identified an oral RfD for fluoride of 0.08 milligrams per kilograms per day (mg/kg/day) based on studies of severe dental fluorosis among children in the six months to 14 year age group (USEPA, 2010b). The “Exposure and Relative Source Contribution Analysis” (USEPA, 2010c) concluded that the RSC values for drinking water range from 40 to 70 percent, with the higher values associated with infants fed with powdered formula or concentrate reconstituted with residential tap water (70%) and with adults (60%). The major contributors to total daily fluoride intakes for these age groups are drinking water, commercial beverages, solid foods and swallowed fluoride-containing toothpaste (USEPA, 2010c).
Summary of Review Results
The Agency has determined that a revision to the NPDWR for fluoride is not appropriate at this time. EPA acknowledges information regarding the exposure and health effects of fluoride (as discussed later in the “Health Effects” and “Occurrence and Exposure” sections). However, with EPA’s identification of several other significant NPDWRs as candidates for near-term revision (see Sections VI.B.3 and VI.B.4),
potential revision of the fluoride NPDWR is a lower priority that would divert significant resources from the higher priority candidates for revision that the Agency has identified, as well as other high priority work within the drinking water office.
These other candidates for revision include the Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules (D/DBPRs) that apply to approximately 42,000 PWSs, and for which EPA has identified the potential to further reduce Start Printed Page 3532bladder cancer risks attributed to exposure to DBPs; the Surface Water Treatment Rules, for which the Agency has identified the potential to further reduce risks from a myriad of serious waterborne diseases (e.g., giardiasis, cryptosporidiosis, legionellosis, hepatitis, meningitis and encephalitis) for approximately 12,000 surface water systems; and the pending revisions to the lead and copper NPDWR which apply to approximately 68,000 PWSs.
While EPA has evaluated the available health effects and exposure information related to fluoride (as discussed later in the “Health Effects” and “Occurrence and Exposure” sections), the Agency also recognizes that new studies on fluoride are currently being performed. These include new studies that address health endpoints of concern other than dental fluorosis. Based on the NRC recommendations, EPA evaluated dental fluorosis for the purposes of this action. EPA will continue to monitor the evolving science, and, when appropriate, will reconsider the fluoride NPDWR’s relative priority for revision and take any other available and appropriate action to address fluoride risks under SDWA.
Finally, most community water systems (CWSs) that provide fluoridation of their drinking water have already lowered their fluoridation level to a single level of 0.7 mg/L from a previous range of 0.7 to 1.2 mg/L to accommodate the updated PHS recommendation (U.S. Department of Health and Human Services, 2015). The U.S. Food and Drug Administration (FDA) also issued a letter to bottled water manufacturers recommending that they not add fluoride to bottled water in excess of the revised PHS recommendations (FDA, 2015). In addition, the FDA stated it intends to revise the quality standard regulation for fluoride added to bottled water to be consistent with the updated PHS recommendation. Therefore, EPA anticipates that a significant portion of the population’s exposure to fluoride in drinking water, as well as some commercial beverages that use fluoridated water from CWSs and certain bottled water, has already been or will be reduced. Notwithstanding this action’s decision, EPA will continue to address risk associated with fluoride in drinking water, with a specific focus on the small systems with naturally occurring fluoride in their source waters.
Initial Review
EPA did not identify any recent, ongoing or pending action on fluoride that would exclude fluoride from the Six-Year Review 3.
Health Effects
The NRC (2006a) evaluated the impact of fluoride on reproduction and development, neurotoxicity and behavior, the endocrine system, genotoxicity, cancer and other effects, in addition to the tooth and bone effects. At fluoride levels below 4.0 mg/L, the NRC found no evidence substantial enough to support adverse effects other than severe dental fluorosis and skeletal fractures. The NRC concluded that the available data were inadequate to determine if a risk of effects on other endpoints exists at an MCLG of 4.0 mg/L and made recommendations for additional research.
EPA assessments (USEPA, 2010b; 2010c) found that the RSC values are lower than the RSC of 100 percent used to derive the original MCLG of 4.0 mg/L, where EPA assumed that drinking water was the sole source of exposure to fluoride. EPA has concluded that information on the dose-response and exposure assessment may support lowering the MCLG to reflect levels that would protect against risk of severe dental fluorosis and skeletal fractures.
As part of this Six-Year Review, EPA reviewed health effects data on the impact of fluoride on reproduction and development, neurotoxicity and behavior, the endocrine system, genotoxicity, cancer and other effects that were identified by the NRC as requiring additional research (NRC, 2006a). EPA noted limitations in some of these studies such as lack of details and confounding factors. Overall, the new data were insufficient to alter the NRC conclusion that severe dental fluorosis is the critical health effects endpoint for the MCLG.
Based upon the recommendations of the NRC, EPA has evaluated dental fluorosis as a critical endpoint of concern for this Six-Year Review (USEPA, 2010b; 2010c). However new studies are underway to examine other health endpoints (i.e., developmental neurobehavior effects, endocrine disruption and genotoxicity). One example is an ongoing National Toxicology Program (NTP) systematic review of animal studies that examined the impact of fluoride on learning and memory (NTP, 2016). For more information about fluoride developmental neurotoxicity visit the National Toxicology Program Web site at https://ntp.niehs.nih.gov/?pubhealth/?hat/?noms/?fluoride/?neuro-index.html. Additional information related to the review of the fluoride NPDWR is provided in the “Six-Year Review 3 Health Effects Assessment Summary Report” (USEPA, 2016h).
Analytical Feasibility
The current PQL for fluoride is 0.5 mg/L (USEPA, 2009a). EPA has not identified any changes in analytical feasibility that could limit its ability to revise the MCL/MCLG for fluoride.
Occurrence and Exposure
EPA analyzed fluoride occurrence using the SYR3 ICR database, which contains fluoride analytical results from approximately 47,000 PWSs in 49 states/entities from 2006 to 2011. Sample records for fluoridated water (i.e., in which a system adds fluoride to maintain a concentration in the 0.7 to 1.2 mg/L range) were omitted from the analysis because the fluoridated systems would not be impacted by revisions to the fluoride NPDWR. EPA estimated the number and percent of systems that have mean fluoride concentrations exceeding various benchmarks and the corresponding estimates of population served by those systems. The data indicated that about 130 systems (0.3 percent), serving approximately 60,000 people (0.03 percent), had an estimated system mean concentration exceeding the current MCL of 4.0 mg/L, whereas more than 900 systems (2 percent), serving approximately 1.5 million people (0.8 percent), had an estimated system mean concentration greater than the SMCL of 2.0 mg/L. Among these systems, many are small systems (serving fewer than 10,000 people) and very small systems (serving fewer than 500 people). Evaluations based on mean (or average) fluoride concentrations generally reflect an approximation of chronic (long-term) exposure. It is important to note that these average concentration-based evaluations help to inform Six-Year Review results, but do not assess compliance with regulatory standards nor should be viewed as compliance forecasts for PWSs.
Treatment Feasibility
A BAT or small system compliance technology for fluoride was not established in the Code of Federal Regulations (40 CFR 141.62). However, EPA (1998d) identified activated alumina and reverse osmosis as BATs for fluoride.
Activated alumina is the most commonly used treatment technology for fluoride removal. It is capable of removing fluoride to concentrations well below the MCL of 4.0 mg/L, but with a shortened media life at lower target concentrations. Membrane technologies, such as reverse osmosis, nanofiltration, and electrodialysis, are Start Printed Page 3533also capable of removing fluoride to very low levels (<0.3 mg/L). They are often used to remove fluoride along with other contaminants such as total dissolved solids, arsenic, and uranium. In general, these technologies are costly and complex to operate—and thus likewise present potential challenges for small water systems (USEPA, 2014a).
*Original notice online at https://www.federalregister.gov/documents/2017/01/11/2016-31262/national-primary-drinking-water-regulations-announcement-of-the-results-of-epas-review-of-existing
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