I’m somewhat surprised that this study has no control group or that the findings were not compared to a town of similar size with no fluoride. Comparing results to national statistics is not very informative. In a limited study such as this observing health effects other than dental fluorosis is unlikely.
Sezgin BI, Onur ŞG, Menteş A, Okutan AE, Haznedaroğlu E, Vieira AR. Two-fold excess of fluoride in the drinking water has no obvious health effects other than dental fluorosis. J Trace Elem Med Biol. 2018 Dec;50:216-222. doi: 10.1016/j.jtemb.2018.07.004. Epub 2018 Jul 11.
BACKGROUND: There is concern that fluorides in the drinking water is hazardous to health.
METHODS: We conducted an observational study in the village of Hanliyenice (population 280), Turkey, which has 2.5 times higher than optimal levels of fluoride in the drinking water and evaluated all children 7-13 years of age (N = 30). We collected information on dental decay, fluorosis, daily water consumption and diet, child history and her family history of cancer, cardiovascular risks/diseases, and asthma, and obtained a blood sample for extraction of genomic DNA. We genotyped ten single nucleotide polymorphisms in aquaporins.
RESULTS: As expected, a high number of children were dental caries free (19 out of 30) and had fluorosis (25 out of 30). Family history of cancer, cardiovascular events, and asthma was not different from the expected figures based on Turkey. One variant just upstream of AQP5 was associated with being fluorosis free. (G allele of AQP5 rs296763, p = 6.0E-6).
CONCLUSIONS: Exposure to levels of fluoride twice as high than the optimum in the drinking water increases the prevalence of fluorosis, dramatically decreases dental caries, and does not increase the risk of cancer, cardiovascular events, and asthma.