Fluoride Toxicity - Chronic Toxicity

Chronic Toxicity

In India an estimated 60 million people have been poisoned by well water contaminated by excessive fluoride, which is dissolved from the granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia.

The only generally accepted adverse effect of fluoride at levels used for water fluoridation is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and usually only an aesthetic concern. Compared to unfluoridated water, fluoridation to 1 mg/L is estimated to cause fluorosis in one of every 6 people (range 4–21), and to cause fluorosis of aesthetic concern in one of every 22 people (range 13.6–∞). Here, "aesthetic concern" is a term used in a standardized scale based on what adolescents would find unacceptable, as measured by a 1996 study of British 14-year-olds.

Consumption of fluoride at levels beyond those used in fluoridated water for a long period of time causes skeletal fluorosis. In some areas, particularly the Asian subcontinent, skeletal fluorosis is endemic. It is known to cause irritable-bowel symptoms and joint pain. Early stages are not clinically obvious, and may be misdiagnosed as (seronegative) rheumatoid arthritis or ankylosing spondylitis.

Other adverse effects may be possible at fluoride intake levels above the recommended dosage, and defluoridation is recommended in these cases. In 1986, the United States Environmental Protection Agency (EPA) established a maximum contaminant level (MCL) for fluoride at a concentration of 4 milligrams per liter (mg/L), which is the legal limit of fluoride allowed in the water. In 1993, a review by the National Academy of Sciences conducted at the behest of EPA concluded that the 4 mg/L MCL was appropriate. However, in 2006, a 12-person committee of the US National Research Council (NRC) reviewed the health risks associated with fluoride consumption and came to the differing conclusion that the MCL should be lowered. In response to these studies, the EPA has made no change to the MCL. U.S. government officials lowered recommended limits for fluoride in water on Friday Jan. 7, 2011, saying some children may be getting tooth damage from too much. The Health and Human Services Department lowered its recommended levels to 0.7 milligrams of fluoride per liter of water -- the lower limit of the current recommended range of 0.7 to 1.2 milligrams. see:http://www.reuters.com/article/2011/01/08/us-usa-fluoride-idUSTRE7064CM20110108

Excess fluoride consumption has been studied as a factor in the following:

• A weakening of bones, leading to an increase in hip and wrist fracture. At the level used in fluoridated water, decreased fractures are expected, but the U.S. National Research Council found the overall evidence "suggestive but inadequate for drawing firm conclusions about the risk or safety of exposures at ", but states that fractures do seem to increase as fluoride is increased from 1 mg/L to 4 mg/L, suggesting a "continuous exposure-effect" dose-response relationship at these levels.

• Adverse effects on the kidney. Within the recommended dose, no effects are expected, but chronic ingestion in excess of 12 mg/day are expected to cause adverse effects, and an intake that high is possible when fluoride levels are around 4 mg/L. Those with impaired kidney function are more susceptible to adverse effects.

• Four epidemiological studies have noted a correlation between increased fluoride and low IQ. The most rigorous of these compared an area with mean water concentration of 0.36 ± 0.15 mg/L (range 0.18–0.76 mg/L) to an area with 2.47 ± 0.79 mg/L (range 0.57–4.50 mg/L). Most of these studies did not publish important details, making them difficult to evaluate. If these correlations are caused by fluoride, the mechanism is not known, but the National Research Council speculates that effects on the thyroid could lead to poor test results. Two Chinese meta-analyses which included the previously mentioned studies have also noted this correlation. The high-fluoride areas studied had fluoride levels above those used in water fluoridation.

• The NRC report stated that "many of the untoward effects of fluoride are due to the formation of AlFx complexes". This topic has been identified previously as cause for concern. The NRC noted that rats administered fluoride had twice as much aluminum in their brains. When water (1 ppm fluoride) is boiled in aluminum cookware more aluminum is leached and more aluminum fluoride complexes are formed. However, an epidemiological study found that a high-fluoride area had one-fifth the Alzheimer's that a low-fluoride area had, and a 2002 study found that fluoride increased the urinary excretion of aluminum.

• Fluoride's suppressive effect on the thyroid is more severe when iodine is deficient, and fluoride is associated with lower levels of iodine. Thyroid effects in humans were associated with fluoride levels 0.05–0.13 mg/kg/day when iodine intake was adequate and 0.01–0.03 mg/kg/day when iodine intake was inadequate. Its mechanisms and effects on the endocrine system remain unclear.