In the 1990s, behaviors exhibited by MCS sufferers were hypothesized by some to reflect broader sociological fears about industrial pollution and broader societal trends of technophobia and chemophobia.These theories have attracted criticism.In Canada, in 2017, following a three-year government inquiry into environmental illness, it was recommended that a public statement be made by the health department.A 2018 systematic review concluded that the evidence suggests that abnormalities in sensory processing pathways combined with peculiar personality traits best explains this condition. Diagnosis
In practice, diagnosis relies entirely upon the self-reported claim that symptoms are triggered by exposure to various substances.Many other tests have been promoted by various people over the years, including testing of the immune system, porphyrin metabolism, provocation-neutralization testing, autoantibodies, the Epstein–Barr virus, testing for evidence of exposure to pesticides or heavy metals, and challenges involving exposure to chemicals, foods, or inhalants. None of these tests correlate with MCS symptoms, and none are useful for diagnosing MCS.The stress and anxiety experienced by people reporting MCS symptoms are significant. Neuropsychological assessments do not find differences between people reporting MCS symptoms and other people in areas such as verbal learning, memory functioning, or psychomotor performance. Neuropsychological tests are sensitive but not specific, and they identify differences that may be caused by unrelated medical, neurological, or neuropsychological conditions.Another major goal for diagnostic work is to identify and treat any other medical conditions the person may have.
In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of childrens teeth during tooth development; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health. A chronic fluoride ingestion of 1 ppm of fluoride in drinking water can cause mottling of the teeth (fluorosis) and an exposure of 1.7 ppm will produce mottling in 30%–50% of patients. Chemical structure
Sodium fluoride is an inorganic ionic compound, dissolving in water to give separated Na+ and F− ions. Like sodium chloride, it crystallizes in a cubic motif where both Na+ and F− occupy octahedral coordination sites; its lattice spacing, approximately 462 pm, is somewhat smaller than that of sodium chloride. Occurrence
The mineral form of NaF, villiaumite, is moderately rare. It is known from plutonic nepheline syenite rocks. Production
NaF is prepared by neutralizing hydrofluoric acid or hexafluorosilicic acid (H2SiF6), both byproducts of the reaction of fluorapatite (Ca5(PO4)3F) from phosphate rock during the production of superphosphate fertilizer. Neutralizing agents include sodium hydroxide and sodium carbonate. Alcohols are sometimes used to precipitate the NaF:

HF  +  NaOH  →   NaF  +  H2OFrom solutions containing HF, sodium fluoride precipitates as the bifluoride salt sodium bifluoride (NaHF2). Heating the latter releases HF and gives NaF. HF  +  NaF  ⇌   NaHF2In a 1986 report, the annual worldwide consumption of NaF was estimated to be several million tonnes. See also
Cryolite
Fluoride therapy

References
External links
"Sodium fluoride".