The Environmental and Health Concerns Associated with Fluoride and by vivi07

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									The Environmental and Health Concerns Associated with Fluoride and Water Fluoridation Systems Genandrialine L. Peralta Environmental Engineering Graduate Program University of the Philippines, Diliman Introduction The global burden of disease due to fluoride in drinking water had been estimated to be 24 million from dental fluorosis and 10 million from skeletal fluorosis (WHO 2006). However, other estimates have reported that these are for China alone and may be only half of the actual burden of disease (Fewtrell et al 2006). Dental fluorosis is a specific disturbance of tooth formation caused by excessive fluoride intake during the development of teeth. It is characterized by opaque white patches in the dental enamel that may become stained yellow to a darker color and could destroy normal tooth structure. Skeletal fluorosis is a crippling bone disease that affects hips, joints and back after prolonged ingestion of fluoride. Additional health outcomes due to ingestion of fluoride have been reported such as cancer, increased bone fractures (Hillier et al 2000, Diesendorf et al 1997), Down syndrome, reproductive effects, and neurodevelopmental disorders but these have no consistent evidence to date. Fluoride has been reported to offer both beneficial and detrimental effects on human health. The debate continues among polarized groups on the benefits and risks of fluoride in drinking water, one more ardent than others (Colquhon 1998). As early as 1952, public opposition started on the so-called “mass medication” of fluoride in London (Sykes 1952). Three years after, Finlayson suggested that instead of adding 1 ppm of fluoride to water supply, it might be wise to focus on efforts at improvement of dental conditions of school children and promoting oral hygiene especially on the use of toothbrush since this would be a valuable and safer solution to the reduction of dental caries and improved oral health rather than water fluoridation (Finlayson 1955). Strong evidence based research concluded that low level of fluoride in drinking water does reduce dental caries but adds to dental fluorosis and that topical action of fluoride is more predominant in preventing dental caries than ingestion (Ayoob and Gupta 2006). Many communities add fluoride to their drinking water to promote dental health while in some countries fluoride is naturally occurring at elevated concentrations in their water sources. It has been reported that excessive fluoride intake from multiple sources can have negative consequences on bones, teeth and the brain. These multiple sources are from processed foods, beverages, swallowed toothpastes and mouthwash, pesticides, wine and tea especially brick tea (IPCS 2002). However, this fluoride added to drinking water to improve dental health is disposed in various ways at levels that could have subtle effect on the aquatic ecosystem such as fish, mussels and crabs (Camargo 2003).

This paper provides a short review to present the reported health concerns related to fluoride ingestion of humans found in drinking water as well as environmental effects on aquatic ecosystems especially organisms such as fish and crabs. Fluoride Standards in Drinking Water The WHO global drinking water quality guideline value for fluoride which provides protection against dental caries (tooth decay) is 1.5 mg/L (WHO 2004). Many countries, when developing their national standards for drinking water for fluoride, have deviated from this guideline such as the USA with 4 mg/L as primary standard and 2 mg/L as secondary standard (USEPA 2007). Fluoride has been classified as an inorganic contaminant by USEPA. The basis for this value set by USEPA has been that some people who drink water containing fluoride in excess of 4 mg/L over many years could get bone disease, including pain and tenderness of the bones. USEPA has also set a secondary fluoride standard of 2 mg/L to protect against dental fluorosis. In its website, there is a warning about dental fluorosis – “whether in moderate or severe forms, dental fluorosis is manifested by a brown staining and/or pitting of the permanent teeth. This problem occurs slowly while the teeth are only developing and before they erupt from the gums. Therefore, it is advised that children under nine years old should not drink water that has more than 2 mg/L of fluoride” (USEPA 2007). Many countries such as Australia, New Zealand, Japan, Singapore, China, Fiji, Philippines, and Cambodia have adopted and approved the drinking water fluoride standard within the range of 0.7 – 1.0 mg/L to protect dental health. In setting the standard for fluoride, other sources of intake were accounted for such as fluoridated salt, milk, sugar, tea, toothpastes, varnishes, rinses, and supplements. These sources aside from seafood may very well provide the needed protection without having to fluoridate the municipal water supplies. Naturally occurring fluoride Fluoride is widely distributed in the lithosphere mainly as fluorspar, fluorapatite and cryolite, and is recognised as the 13 th most common element in the earth’s crust. It is found in seawater at a concentration of around 1.2 - 1.4 mg/liter, in ground waters at concentrations up to 67 mg/liter, and in most surface waters at concentrations less than 0.1 mg/liter. Fluoride is also found in foods particularly fish and tea (IPCS 2002, WHO 2002, WHO 2005). In 2006, WHO has reported the natural distribution of fluoride worldwide. Waters high in fluoride are mainly calcium-deficient groundwaters in basement aquifers, in geothermal waters and in some sedimentary basins. Groundwaters with high fluoride concentrations occur in many areas of the world including large parts of Africa, China, the Eastern Mediterranean and southern Asia (India, Sri Lanka). One of the best-known high fluoride belts on land extends along the East African Rift from Eritrea to Malawi. There is another belt from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China and similar belts in the Americas and Japan. In these areas, for example in China,


concentrations above 4 mg/L of fluoride had been detected in their drinking water usually from wells. Asian countries with natural sources of elevated fluoride in groundwater are China, India, Pakistan, Mongolia and the Philippines. Elevated level of flouride in groundwater was found in the coastal areas of Cavite City, Noveleta, Bacoor and Kawit, Cavite City, Philippines, which is 34 km south of Manila. Anthropogenic sources of fluoride Fluoride is found in insecticides, rodenticides, floor polishes, petroleum and aluminum industries, coal burning, glass etching and timber preservation. Hydrogen fluoride/hydrofluoric acid is used in the semiconductor industry, the manufacture of chemicals, solvents and plastics, and in laundries. Phosphate rock has an estimated two to four percent fluoride. Phosphate fertilizers are produced by adding acid to pulverized phosphate rock - either sulfuric or phosphoric acid. Significant quantities of fluoride (hydrogen fluoride and silicon tetrafluoride) are released but captured in the pollution control scrubbers. Hydrofluorosilicic acid is the waste product from the "scrubbers" that is used to fluoridate approximately 90% of US public drinking water systems (Ayoob and Gupta 2006, IPCS 2002). Water fluoridation practices In some parts of the world where natural fluoride was not sufficient in their drinking water to prevent caries, water fluoridation programmes have been established in many countries (WHO 2001). The optimal level is usually around 1 mg/liter and is added in water treatment plants. Since fluoride is odorless and tasteless, there is no perceptible change to the water. The usual chemicals used for fluoridation are: hexafluorosilicic acid, disodium hexafluorosilicate or sodium fluoride. A fluoridation programme requires good maintenance and a specially designed plant: fluoridation chemicals are corrosive in concentrated form and must be stored and handled according to safe working practices. Several countries practiced water fluoridation for over 50 years with remarkable improvement in oral health. Water fluoridation is practiced mainly in English speaking countries where the percentage of population using fluoridated water are: USA (67%), UK (10%), Singapore (100%), with Australia, Brazil, Canada, Ireland, Israel, Malaysia, New Zealand, and South Africa (30-70%). In 2001, an economic evaluation of the cost effectiveness of water fluoridation was made which concluded that it still offered significant cost savings compared to restoration cost of dental caries (Griffin et al 2001). However, data from WHO (2006) showed that, in general, tooth decay trends have been reduced significantly in developed countries in the last 25 years, in both fluoridated and unfluoridated countries. This may be attributed to improved personal hygiene especially toothbrushing, better diet, better economic status as there is available water from the tap along with toothpaste and toothbrush. Some places like the two towns in Scotland showed that there was an increase in the prevalence of dental caries since the cessation of water fluoridation (Attwood and Blinkhorn 1988) just like La Salud, Cuba (Fischer 2000).


Monitoring and operation of water fluoridation system In drinking water, monitoring of fluoride concentration requires specific laboratory equipment and skilled personnel since there is a narrow range at low levels (0.7-1.5 mg/L) which can spell the difference between beneficial and adverse health effects. To analyze for fluoride, the ion selective membrane electrode is used whether as an online sensor or manual in situ meter. Where chlorination is practiced for disinfection by water service providers, monitoring residual chlorine is still a challenge which brings to mind whether there is capacity for proper dosing and measurement of fluoride when applied to water supplies. This may not be possible in many developing nations due to possible malfunctions in systems which may not be detected in a timely manner. For example in the UK, the following safety measures are in place…”The process of fluoride monitoring is automatic and is carried out by equipment which itself is regularly checked to ensure its accuracy. If at any time the fluoride level should exceed the permitted level, a warning is sounded in the control room and the whole plant is automatically shut down. The monitor itself also incorporates a fail-safe shut down of the fluoridation plant should the monitor or controller become faulty” (UKBFS 2004). In the US alone, there were around 17 incidences of fluoridation equipment malfunction, with associated deaths and poisoning. Worst incident reported was in Alaska in 1992 where 296 people were poisoned with fluoride intoxication with gastrointestinal symptoms and one person died.The final report cited the following reasons for the system failure such as human error, mechanical failure, lack of safety features and failure to comply with regulations (Foulkes 1994). This shows the complexity of a water fluoridation system which cannot be handled by a small water utility. In Canada, the publication from British Columbia Workers’ Compensation Board entitled Water Fluoridation - A Manual of Standard Practice (1993) has addressed the list of problems identified by those investigating the Hooper Bay (Alaska) incident. These are: operator has minimal training; no fluoride testing by operator; slow response to high fluoride values identified by testing; inadequate labeling of pumps and piping; electrical wiring that signals water pump was corroded (water pump did not turn on); high water level indicator in holding tank that signals on/off operation of water pump and fluoride pump was not activated (fluoride pump was in continuous operation); defective ball valve in fluoride pump allowed pump to operate at seven times the normal rate; no daily or continuous monitoring of treated water; and possible cross-connection between treated water in the holding tank and fluoride solution in tank (siphon action possible upon incorrect use of long supply hose). In the USA many fluoridation plants serve small communities such as schools and relatively undeveloped remote villages such as in Hooper Bay, Alaska. Training and supervision of water plant operators in such locations tends to be less stringent than in the highly regulated UK water industry, and equipment such as continuous recording fluoride monitors are not used. This scenario is typical in developing countries.


Health effects of high fluoride concentration Elevated fluoride concentration in water has been associated with dental and skeletal fluorosis, severe enamel fluorosis, osteosarcoma (bone cancer), osteoporosis, reduced IQ (Xiang et al 2003) and neurological effects. More reported symptoms suspected to be due to fluoride are increased bone fractures, Down syndrome and reproductive effects (WHO/IPCS 2002). In Australia, a review of literature on hip fractures, skeletal fluorosis, the effect of fluoride on bone structure, fluoride levels in bones and osteosarcomas have been reported to provide the existence of causal mechanisms by which fluoride damages bones (Diesendorf et al 1997). Grandjean and Landrigan (2006) identified fluoride, together with manganese and perchlorate, as emerging neurotoxic substances. Common neurodevelopmental disorders could be in the form of autism, attention deficit disorder, mental retardation, and cerebral palsy. They reported that as many as 200 additional chemicals are known to cause clinical neurotoxic effects in adults. However, the toxic effects of such chemicals in the developing human brain (such as the fetus) are not known which does not provide protection to children in terms of regulation. In Japan, Tsutsui et al (2000) investigated the prevalence of dental caries and fluorosis in Japanese communities with up to 1.4 ppm of naturally occurring fluoride. A total of 1,060 10- to 12-year-old lifetime residents were examined and found that the prevalence of fluorosis was directly related to the concentration of fluoride in the drinking water. Wang et al (2007) examined 524 children (exposed and controls) aged 8 to 12 years old in China's Shanxi province for fluoride exposures and the effects on intellectual functioning and growth. The families were exposed to naturally occurring high concentrations of fluoride through well water, as high as 8.3 milligrams per liter (mg/L) in the study area and about 0.5 mg/L in the control group. In general, children in the high fluoride group had a four-point reduction in IQ score as compared to the control children. Similar observations were made by Xiang et al in 2003 on the effect of fluoride in drinking water on children's intelligence. These results of Wang et al (2007) on IQ reduction after continuous ingestion of fluorideladen well water, have significant public health implications especially in countries where water fluoridation is practiced and there are other exposures to fluoride aside from drinking water such as in the US and other English-speaking countries. Though the drinking water concentrations of fluoride observed in this study are way above the concentrations in US public drinking water supplies, children and adults may be receiving excess fluoride through multiple sources (drinking water, bottled water and soft drinks, toothpaste, mouth rinses) and the additive effect could very well be similar to the situation in Shanxi Province.


Tea drinking is the most popular drink worldwide from America to Europe and especially in Asia. However, tea has natural fluoride levels since the tea leaves easily absorb fluoride from the soil. Cao et al (2004) reported that heavy tea drinkers of about 4 cups daily consumption of black tea and which use water fluoridated water of 0.8 to 1.0 ppm fluoride to prepare their tea might have excessive daily fluoride intake which could be potentially harmful. On one hand, in the study of Malde et al, the possible effect of original fluoride concentration in the water on the fluoride release from tea was tested and the possible capacity of commercial tea leaves to absorb fluoride from high-fluoride water. In low-fluoride water, fluoride is easily released from tea leaves. Depending upon the fluoride content of the water, dried tea leaves were able also to absorb fluoride. Thus, if a cup of tea is made from high-fluoride water, the fluoride concentration of the infusion may actually be lower than the original fluoride concentration of the water (Malde et al 2006). Fluoride effects on fish and organisms Although effective for oral health, fluoride at low concentrations in bodies of water may be toxic to several organisms as reported by several researchers. The water fluoridated effluents are disposed of and find their way in rivers, lakes, and groundwater. As early as 1962, Bicknell already raised the issue of the possible harm by the discharge into rivers of fluoridated effluents on fishes and plankton. Osterman (1990) used the mass balance approach to evaluate this perceived risk in Montreal where it was found that water fluoridation would raise average aquatic fluoride levels in the waste water plume immediately below effluent outfall by only 0.05-0.09 mg/L. However, it was suspected that fluoridated water in sewage would be diluted by rain and ground water infiltration, fluoride removal during secondary sewage treatment, and diffusion dynamics at effluent outfall which would eliminate fluoridation-related environmental effects. (Osterman 1990). Freshwater fish may resist higher fluoride concentrations in hard water than in soft water with hardness average value of 22 ppm CaCO3 (Sigler and Neuhold 1972). The fish were reported to show signs of intoxication due to fluoride found in rivers of western USA with concentrations from 1 ppm to 14 ppm. The F sources were mostly from natural sources of cryolite, apatite and sedimentary phosphate rocks that leached fluoride to the environment. Atmospheric pollution from industrial sources could have contributed as well. Two types of trouts (rainbow trout and brown trout) in soft water aquaria exposed to high concentrations of fluoride showed hypoexcitability, darkened backs and a decrease in respiration before their death (Camargo and Tarazona 1991). They reported LC50 values of 78 ppm and 114 ppm for rainbow trout and brown trout respectively within a one week period. Neuhold and Sigler in 1960 also found the adverse effects of sodium fluoride on carp and rainbow trout.


In Northwest USA and British Columbia, Canada, the migration of salmon species was inhibited and therefore reduced the fish stocks (Foulkes and Anderson 1994). The uptake of fluoride was studied in blue crab in North Carolina, USA which showed accumulation of up to 90 ppm after a 90-day exposure. The crab muscle tissue, which is the part consumed as seafood, can accumulate enough fluoride to present a potential public health problem (Moore 1971). Camargo and Tarazona (1990) also found acute fluoride toxicity among freshwater benthic macroinvertebrates in soft water. Accidental releases of fluoride were simulated in Grenoble, France in an experimental pond for 30 days. Twenty-four hours after the release, around 99.8% of the fluoride was found in sediments (67.8%) and in water (32%), and the biological agents contained only 0.2% fluoride. The fluoride concentration stabilized to 22 ppm in water after one day and to near background level of 0.2 ppm the rest of the month. Despite an exposure to high concentrations of 5,000 ppm at the beginning of the accidental release, no visible toxic effects were observed on the biological components such as plants, algae, molluscs, and fish (Kudo and Garrec 1983). They further concluded that since the experiment was carried out in March, which is not yet spring and with some snow, the results of this experiment suggest that the toxicity to the biological agents may not be the same throughout the year and temperature effects may have influence on the uptake of fluoride by organisms. Biosynthesis of organofluorides Many inorganic contaminants may be transformed into substances more toxic than the pollutants in their original form, e.g. mercury becoming methyl mercury. Reports claim that some plants can synthesize organic fluoride compounds (fluoroacetate and fluorocitrate) from inorganic fluorides. The organic forms are very toxic to living things (IPCS 2002). Little is known on fluoride transformation and distribution into various environmental media and its effects on humans. Conclusions Although there is substantially large evidence to attribute dental and skeletal fluorosis due to fluoride ingestion in humans, there are not enough studies on the environmental effects of fluoride in aquatic ecosystems. The weight of the evidence indicates the presence of unknown environmental effects which have implications on food security and environmental sustainability. There is a need to understand the behavior and distribution of fluoride in various environmental media to track its environmental pathway including its transformation into organic fluoride. Water fluoridation should be seriously evaluated whether the benefits far outweigh the risks, both known and unknown. The decision to fluoridate or not should consider the following factors. a) the existing concentration of fluoride in the local water supply b) climatic conditions (temperature) and the volume of water consumed c) risk of tooth decay due to sugar consumption d) public awareness on oral health


e) availability of alternative sources of fluoride to the general population f) the possible ecosystem effects on aquatic environment Recommendations The following are recommended for future studies to advance the knowledge on impacts of fluoride on health and the environment. (a) the increase in dental fluorosis among children in warmer climates than in temperate climates, (b) background fluoride concentrations (inorganic and organic species) in soil and water from natural and man made sources, (c) biosynthesis of fluoride to organic forms which are more toxic, (d) biomagnification and bioavailability of fluoride to aquatic and terrestrial biota and its sublethal effects especially at higher temperatures, (e) environmental pathways of fluoride (f) fluoride removal technologies especially in drinking water (g) more evaluation of water fluoridation systems Acknowledgement The author is grateful for the fellowship (May 15 - June 30, 2007) from the Japan Society for Promotion of Science (JSPS) and the opportunity to work with Prof Shinichiro Ohgaki at the University of Tokyo, Japan. The staff and faculty of the Department of Civil Engineering of Tokyo Institute of Technology especially Prof O. Kusakabe, Dr J. Takemura, and Ms M. Ishii have been very helpful throughout the fellowship. References Attwood D and Blinkhorn AS. 1988. Trends in Dental Health of Ten-Year old Schoolchildren in South-West Scotland after Cessation of Water Fluoridation. Lancet. July 30, 1988 (266-267). Ayoob S and Gupta A K. 2006. Fluoride in drinking water: a review on the status and stress effects, Critical Reviews in Environmental Science and Technology, 36 (6) 433 487 Bicknell F. 1962. Fluoridation of Water Supplies. Letters to the Editor. Lancet. July 28, 1962 (200). Camargo JA. 2003. Fluoride toxicity to aquatic organisms: a review. Chemosphere 50: 251–264. Camargo J A and Tarazona J V. 1990. Acute toxicity to freshwater benthic macroinvertebrates of fluoride ion (F-) in soft water. Bull. Environ. Contain. Toxicol. 45, 883-887.


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