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　　mild case of fluorosis, with faint white mottling.

　　The World Health Organization cautions that fluoride levels above 1.5 milligrams per liter leaves the risk for fluorosis.[34] Consumption of water exceeding 10 ppm fluoride has been shown to lead to pathological changes in bone structure, and skeletal fluorosis.[35] [36] 0.07 – 1.2 milligrams per liter of fluoride is considered to be the optimal level. A CDC evaluation concluded that prevalence of some level of fluorosis among children and adolescents in the United States had increased by from 22.8% in 1986 – 1987 to 32% in 1999 – 2002.[37] Debilitating environmental fluorosis of a portion of the population is a problem in several developing countries, where it is complicated by malnutrition. The effects of skeletal fluorosis can be slowly reversed through a reduction of fluoride intake and improved diet.[38] To protect against this health organizations in some high fluoride areas endorse providing alternative water sources, or removing fluoride from the water.[39]

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