Fluoride and environmental health: a review

Abstract

The relationship between environmental fluoride and human health has been studied for over 100 years by researchers from a wide variety of disciplines. Most scientists believe that small amounts of fluoride in the diet can help prevent dental caries and strengthen bones, but there are a number of adverse affects that chronic ingestion at high doses can have on human health, including dental fluorosis, skeletal fluorosis, increased rates of bone fractures, decreased birth rates, increased rates of urolithiasis (kidney stones), impaired thyroid function, and lower intelligence in children. Chronic occupational exposure to fluoride dust and gas is associated with higher rates of bladder cancer and variety of respiratory ailments. Acute fluoride toxicity and even death from the ingestion of sodium fluoride pesticides and dental products have also been reported. The distribution of fluoride in the natural environment is very uneven, largely a result of the geochemical behavior of this element. Fluorine is preferentially enriched in highly evolved magmas and hydrothermal solutions, which explains why high concentrations are often found in syenites, granitoid plutonic rocks, alkaline volcanic, and hydrothermal deposits. Fluoride can also occur in sedimentary formations that contain fluoride-bearing minerals derived from the parent rock, fluoride-rich clays, or fluorapatite. Dissolved fluoride levels are usually controlled by the solubility of fluorite (CaF 2 ); thus, high concentrations are often associated with soft, alkaline, and calcium-deficient waters. Although much is known about the occurrence and health effects of fluoride, problems persist in Third World countries, where populations have little choice in the source of their drinking water and food. However, even in developed nations, fluoride ingestion can exceed the recommended dose when sources other than drinking water are ignored.

The effect of non-fluoride factors on risk of dental fluorosis: Evidence from rural populations of the Main Ethiopian Rift

“…While the prevalence of DF in our study was estimated for a relatively young population (having an average age of 17.6 years old), many of these individuals (23.3%) already had severe DF. This is in agreement with the results of multiple studies in which DF has been described as a disease that begins from birth, when uptake of F − by human skeleton is the highest (Ozsvath, 2009;Whitford, 1999). About half of the absorbed F − is quickly incorporated into developing bone and teeth, where nearly all of the body's F − is found, and the remainder is excreted in the urine (Cerklewski, 1997).…”

“…However, there is a high correlation across those elements in the groundwater of the study communities in the MER (Rango et al, 2012), and understanding these associations, therefore, requires much more study. More generally, many of the world's high-F − districts are underlain by crystalline igneous and metamorphic rocks (e.g., parts of India, Sri Lanka, Senegal, Ghana, South Africa, and Scandinavia) or occur in areas of volcanic and associated hydrothermal activity (Ozsvath, 2009). When the groundwater enters into contact with these rocks, it is often soft and Ca-deficient, which allows for higher F − concentrations when equilibrium with fluorite is attained (Ozsvath, 2006).…”

“…Establishing appropriate drinking water standards for F − (i.e., its maximum allowable concentrations) is dependent upon many factors, including climate, diet, and characteristics of the target population (and even within a given region, different subsets of the population may respond differently to the same dose) (Ozsvath, 2009). Some researchers have argued for more stringency than the WHO standards for countries with hot, dry climates (Brouwer et al, 1988), or for the regions where F − content in food is higher than that assumed by WHO (Apambire et al, 1997).…”

Analytical Problems with the Evaluation of Human Exposure to Fluorides from Tea Products

“…A correlation between the rates of dental caries and fluoride concentrations in consumed drinking waters has been known since 1940s (Hardisson et al 2003). Fluorides can improve bone mineralisation by substitution of hydroxyl groups in hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 involved in building of skeletal bone, generating fluoroapatite, Ca 10 (PO 4 ) 6 OHF and Ca 10 (PO 4 ) 6 F 2 , of reduced crystal volume, increased structural stability and decreased mineral solubility (Ozsvath 2009). This can result in the reduction of a risk of osteoporosis.…”

“…Disorders in enamel formation resulting in large gaps in its crystalline structure, mottling of the tooth surface and dental fluorosis are characteristic for fluoride overdose. The excess of fluorides can generate significant disruptive health effects, among them skeletal fluorosis and increased rates of bone fractures; decreased birth rates; increased risk of cancer, in particular bone and blood cancer; increased rates of urolithiasis (kidney stones); and neurotoxicity are the most dangerous (Hardisson et al 2003;Ozsvath 2009;Yi and Cao 2008). Recent data on negative effects of the excess of fluorides on biological activity of proteins and enzymatic systems, resulting, e.g.…”