Page 2: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Fluoride
Part I. Overview and Application
The maximum acceptable concentration (MAC) for fluoride in drinking water is 1.5 mg/L.
2.0 Executive summary
Low levels of fluoride occur naturally in most sources of drinking water in Canada. Fluoride can occur naturally in surface waters from the deposition of particulates from the atmosphere and the weathering of fluoride-containing rocks and soils, and in groundwater from leaching from rock formations. Fluoride is also introduced in the environment by a variety of human activities such as chemical manufacturing plants and waste ponds; the manufacture of aluminum, steel, glass, enamel, brick, tile, pottery, and cement; production of fluorinated chemical and phosphate fertilizer; and metal casting, welding, and brazing.
Health Canada recently completed its review of the health risks associated with fluoride in drinking water. This review assesses all identified human health risks, taking into account new studies and approaches. Based on this review, the guideline for fluoride in drinking water is a Maximum Acceptable Concentration of 1.5 mg/L.
2.1 Health effects
Dental fluorosis is the most widely and frequently studied of all adverse effects of fluoride. It is the effect occurring at the lowest level of fluoride exposure in the population. Mild and very mild dental fluorosis are not considered to be adverse effects, whereas moderate dental fluorosis is found to be an adverse effect, based on its potential cosmetic concern, and is used as the endpoint of concern in the risk assessment used to establish the Maximum Acceptable Concentration. By protecting against a cosmetic effect of moderate dental fluorosis, Canadians are also protected against the adverse health effects of severe dental fluorosis.
Skeletal fluorosis is the most serious adverse health effect clearly associated with prolonged exposure to high levels of fluoride in drinking water. Skeletal fluorosis can occur at very high exposure levels, and has rarely been documented in Canada.
The weight of evidence from all currently available studies does not support a link between exposure to fluoride in drinking water at 1.5 mg/L and any adverse health effects, including those related to cancer, immunotoxicity, reproductive/developmental toxicity, genotoxicity and/or neurotoxicity. It also does not support a link between fluoride exposure and intelligence quotient deficit, as there are significant concerns regarding the relevant studies, including quality, credibility, and methodological weaknesses.
Major sources of exposure to fluoride are water, food and beverages, and dental products. Dental products contain high levels of fluoride and can represent a very important source of exposure, particularly in young children who are more likely to swallow toothpaste. Drinking water can be a significant source of exposure to fluoride; in 2005, community fluoridated drinking water was provided to about 43% of Canadians. To a lesser extent, fluorides are also found in Canadian soils and the atmosphere.
Water containing fluoride levels greater than the MAC of 1.5 mg/L can be treated at both municipal and residential scales through various approaches and technologies. At the municipal level, options include blending of fluoride-rich waters with waters of low fluoride content, the selection of low-fluoride sources and the removal of excess fluoride concentration by treatment processes at public water supply or household level. A wide range of technologies, such as activated alumina, reverse osmosis, lime softening and ion exchange, are capable of reducing excess fluoride levels from drinking water.
At the residential scale, reverse osmosis systems can be used at the point of use, and must be capable of reducing the concentration of fluoride in water to a maximum of 1.5 mg/L to be certified. Distillation systems installed at the point of use are effective to remove inorganic contaminants, including fluoride, and must be capable of reducing fluoride levels to a maximum of 2.0 mg/L to be certified.
2.4 Dental health benefits
Health Canada's Chief Dental Officer has reviewed the available science on dental effects of fluoride, and sought external expert advice from the scientific dental community. Experts provided a recommendation on the optimal level, which was accepted by Health Canada's Chief Dental Officer. As a result, the optimal concentration of fluoride in drinking water for dental health has been determined to be 0.7 mg/L for communities who wish to fluoridate. This concentration provides optimal dental health benefits and is well below the MAC to protect against adverse effects. For more information, consult the findings and recommendations of the fluoride expert panel.
3.0 Application of the guideline
Note: Specific guidance related to the implementation of drinking water guidelines should be obtained from the appropriate drinking water authority in the affected jurisdiction.
The Maximum Acceptable Concentration for fluoride was established based on the segment of the population most at risk of developing dental fluorosis, children 1-4 years old. This MAC is protective of health, provided care is taken to follow Health Canada's recommendations (www.hc-sc.gc.ca/hl-vs/iyh-vsv/environ/fluor-eng.php) regarding other sources of exposure to fluoride, such as dental products.
Frequent monitoring of naturally-occurring fluoride levels is generally not required, as these levels are not expected to change rapidly. Some groundwater sources may have naturally-occurring levels of fluoride significantly above the MAC of 1.5 mg/L. In such cases, the homeowner may wish to consider residential scale treatment or an alternate source of drinking water, especially where young children are exposed on a regular basis.
Short-term exceedances slightly above the guideline value are unlikely to have an effect on health. However, in the event that monitoring data show elevated levels of naturally-occurring fluoride, it is suggested that a plan be developed and implemented to address these situations, with an emphasis on young children.
Municipalities that choose to fluoridate their drinking water supply should establish a full monitoring and reporting program for fluoride levels in drinking water to ensure that the target fluoride level is being applied at all times.
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