NSF International (www.nsf.org) is an independent,global not-for-profit organization that facilitates standards development, and tests and certifies products for the food, water, health sciences and consumer goods industries to minimize adverse health effects and protect the environment. Founded in 1944, NSF is committed to protecting human health and safety worldwide. NSF International is a Pan American Health Organization/World Health Organization (WHO) Collaborating Center on Food Safety, Water Quality and Indoor Environment.
NSF/ANSI 60NSF/ANSI 60
Drinking Water Treatment Chemicals-Health Effects was developed to establish minimum requirements for the control of potential adverse human health effects from products added directly to water during its treatment, storage and distribution. The standard requires a full formulation disclosure of each chemical ingredient in a product to allow for a comprehensive evaluation of the products and their ingredients. The standard requires testing of the treatment chemical products, typically by dosing these in water at 10times the maximum use level (MUL), so that trace levels of contaminants can be detected. A further evaluation of test results is required to determine if the concentrations of any detected contaminants have the potential to cause adverse human health effects. When health effects criteria have not been established for a given product or contaminant, the standard requires that health effects criteria be derived according to the requirements of Annex A prior to approval under this standard.
NSF’s testing and certification program for drinking water treatment products was developed in the late 1980s to ensure that individual U.S. states and waterworks facilities have a mechanism to determine which products are most suitable for use. The NSF certification program requires annual, unannounced inspections of production and distribution facilities to ensure that the products are properly formulated, packaged and transported with appropriate safe guards in place to protect against potential contamination. NSF also requires annual testing and evaluation of each NSF certified product to confirm contaminants do not exceed drinking water health effects criteria.
Properties and Water Applications
Water fluoridation is the practice of adjusting the fluoride content of drinking water. Fluoride is added to water for the public health benefit of greatly reducing the incidence of tooth decay and therefore improving the health of the community. For more information please visit the U.S. Centers for Disease Control and Prevention: www.cdc.gov/fluoridation/.
NSF certifies three products in the fluoridation category:
- 1.Fluorosilicic acid (aka fluosilicic acid or hydrofluosilicic acid)
- 2.Sodium fluorosilicate (aka sodium silicofluoride)
- 3.Sodium fluorideAll three products readily dissociate in water to release fluoride and related ions.
In the case of the fluorosilicates, they fully dissociate to fluoride and silicate ions in association with either hydrogen or sodium ions1. In the case of sodium fluoride,it fully dissociates to form fluoride and sodium ions.Treatment products that are used for fluoridation are specifically addressed in Section 7 of NSF/ANSI 60. The standard requires that the treatment products added to drinking water, as well as any impurities in the products, are supported by an evaluation of potential health effects resulting from exposure to the products or associated contaminants. The following text explains the allowable levels established in the standard for 1) fluoride, 2) silicate and 3) other potential contaminants that may be associated with fluoridation chemicals.
Fluoride Drinking Water Criteria
NSF/ANSI 60 requires, when available, that the U.S.or Canadian regulatory values be used to determine the acceptable level for a chemical of interest. The EPA MCL for fluoride ion in water is 4 mg/Land the Health Canada MAC for fluoride is 1.5 mg/L to protect against skeletal fluorosis. However, in 2003, representatives from the EPA and Health Canada reviewed the evaluation criteria in NSF/ANSI60 and recommended that the TAC and SPAC for fluoride ion in drinking water contributed by fluoridation products be lowered to1.2 mg/L to match the upper bound of the U.S. Public Health Service/Centers for Disease Control recommended fluoride concentration range to prevent dental fluorosis (an aesthetic effect). The Drinking Water Additives Joint Committee for NSF/ANSI 60 supported this recommendation and set the acceptance criteria for fluoride ion equivalent to the maximum recommended fluoride ion dose. For treatment chemicals other than fluoridation products, the allowable fluoride contribution is 0.12 mg/L, or a tenth the TAC.
In 2015, the U.S.Department of Health and Human Services recommended that the optimal range of water fluoridation of 0.7 to 1.2 ppm (mg/L) be updated to an optimal concentration of 0.7 ppm(mg/L)due to observations of increasing amounts of fluoride in food that is processed with fluoridated drinking water. Some U.S.states have elected to adopt this optimal concentration for fluoridation of community water supplies. Testing these chemicals at the higher use level of 1.2 ppm (as is currently done) provides a more conservative screening for contaminants in or associated with use of these products.
More recently, the U.S.Centers for Disease Control and Prevention (CDC) has proposed that the recommended operational range for community water supplies be narrowed to 0.6mg/L to 1.0 mg/L fluoride ion2. The CDC advised that this change is to reflect demonstrated ability of water utilities to maintain control of fluoride concentration around the 0.7 mg/L optimum concentration. The Drinking Water Additives Joint Committee for NSF/ANSI 60 is reviewing whether it should lower the fluoride ion typical use level from 1.2 mg/L to 1.0 mg/L. If this request is approved by the Drinking Water Additives Joint Committee, it will be incorporated into NSF/ANSI 60 in 2019. Silicate Drinking Water Criteria
Fluorosilicates do not require a toxicological assessment specifically for the fluorosilicate ion, because measurable levels of this ion do not exist in potable water at the fluoride concentrations and pH levels typical of public drinking water.3 There is currently no U.S.EPA-derived MCL or Health Canada MAC for silicate in drinking water. The current sodium silicate typical use level (TUL) of 16 mg/L is listed in Table 5.1 of NSF/ANSI 60, which was based on the value for sodium silicate published in the Water Chemicals Codex.4 A fluorosilicate product, applied at its maximum use level (noted below), results in silicate drinking water levels that are substantially below the 16 mg/LTUL. For example, a sodium fluorosilicate product dosed at a concentration into drinking water that would provide the maximum concentration of fluoride currently permitted by NSF/ANSI 60(1.2mg/L) would only contribute 0.8 mg/L of silicate –or 5percent of the TUL allowed by NSF/ANSI6 0f or silicate.
Fluoridation Product Use Levels
Allowable use levels for fluoridation chemicals are limitedby the NSF/ANSI 60 limits for fluoride ion. Per the previous section, the silicate contribution is not a limiting factor. The allowable maximum use levels (MUL) for NSF/ANSI60 certified fluoridation productsin 2018 are:
- 1. Fluorosilicic acid: 6 mg/L
- 2.Sodium fluorosilicate: 2 mg/L
- 3.Sodium fluoride: 2.3 mg/L
Potential Contaminantsin Fluoridation Chemicals
The product review conducted by NSF for a water treatment product considers all chemical ingredients in the product,as well as the manufacturing process, processing aids and other factors that have an impact on the chemicals attributable to the products present in the finished drinking water. The identified chemicals of interest are subsequently evaluated during testing of the product. For example, fluosilicic acid is produced by adding sulfuric acid to phosphate ore. This is typically done during the production of phosphate additives. The manufacturing process is documented by an NSF auditor at the initial audit of the manufacturing site and during each subsequent annual unannounced audit of the facility. The manufacturing process, ingredients and potential contaminants are reviewed annually, and the product is tested for any potential contaminants of interest. A minimum test battery for all fluoridation products includes heavy metals of toxicological concern and radionuclides because they may be contained in phosphate ore.
Many drinking water treatment additives, including fluoridation products, are transported in bulk via tanker trucks to terminals where they are transferred to rail cars, shipped to distant locations or transferred into tanker trucks, and then delivered to the water treatment plants. These tanker trucks, transfer terminals and rail cars are potential sources of contamination. Therefore, NSF also inspects, samples, tests and certifies products at rail transfer and storage depots. It is always important to verify that the location of the product distributor (the company that delivers the product to the water utility) matches that shown in the official NSF listing for the product (available at www.nsf.org).
NSF has compiled data on the levels of contaminants found in or through use of all fluoridation products that have applied for, or have been approved for, certification by NSF under NSF/ANSI 60. The results in Tables 1, 2, and 3 include those from the initial and annual monitoring tests for fluoridation products that NSF certified to NSF/ANSI 60 from2012 to 2017 (Table 1), 2007 to 2011 (Table 2)and 2000 to 2006 (Table 3). This summary includes 245 separate samples analyzed during the time period of 2000 to 2006, 216 samples in the period of 2007 to 2011, and 328 samples in the period of 2012 to 2017. The concentrations reported represent contaminant levels expected when the products are dosed into water at the manufacturer’s maximum use level (MUL). For the time periods summarized below, the typical product certification and evaluation werebased on a fluoride ion dose of 1.2 mg/L. Lower product use levels would produce proportionately lower contaminant concentrations (e.g.a 0.6 mg/L fluoride dose would produce one half the contaminant concentrations listed in Table 1).
The data reported in Tables 1, 2,and 3 demonstrate that very low concentrations of contaminants are associated with fluoridation chemicals. In fact, NSF was only able to detect the reported trace amounts by dosing the chemicals into reagent water at 10times the manufacturer’s maximum use level (as required by NSF/ANSI 60)and then mathematically adjusting the laboratory results to expected field dose. If the products had been dosed into water at the manufacturer’s maximum use level, only one copper contaminant concentration would have been above the analytical method detection limits. This is demonstrated by comparing the results in columns 3 and 4 with the detection limits in column 5. The low concentrations of contaminants documented for this most current time period are explained, at least in part, bythe ongoing effectiveness of NSF/ANSI 60 and the NSF certification program for drinking water treatment additives. The levels in Table 1 are comparable to those documented earlier for the 2000-2011 time period,which is further attested to by a 2004 article in the Journal of the American Water Works Association entitled, “Trace Contaminants in Water Treatment Chemicals.”3
All the fluoridation products tested by NSF, when evaluatedat their maximum use level in water, meet the health effects requirements of NSF/ANSI 60. Arsenic was periodically detected in half of all samples. However, the mean arsenic concentration is 1/50thof the U.S.EPA MCL and none of the samples exceeded 1/10ththe U.S.EPA MCL. The majority of fluoridation products certified by NSF do not contain detectable concentrations of lead, radionuclides or other heavy metals when dosed into water at their maximum use level. In summary, fluoridation products certified by NSF do not contribute a significant contaminant burden to drinking water.
*The full document, including Tables, is at http://fluoridealert.org/wp-content/uploads/nsf.fact-sheet.jan-14-2019.pdf