Safety l Fluoridation Facts 61 original observations.”7 The World Health Organization also judged these cases to represent “a variety of unrelated conditions” and found no evidence of allergic reactions to fluoride.139,140 38. Is fluoride, as provided by community water fluoridation, a genetic hazard? Answer. The best available scientific evidence indicates that drinking water fluoridated at the recommended levels is not a genetic hazard. Fact. Chromosomes are the DNA-containing bodies of cells that are responsible for the determination and transmission of hereditary characteristics. A single chromosome contains many genes which are the functional hereditary units that occupy a fixed location on a chromosome. Many studies have examined the possible effects of fluoride on chromosome damage. In 1993, the National Research Council (NRC) of the National Academies issued a report8 that supported the conclusion that drinking optimally fluoridated water is not a genetic hazard. In a statement summarizing its research8, the NRC stated, “in vitro data indicate that: 1. the genotoxicity of fluoride is limited primarily to doses much higher than those to which humans are exposed, 2. even at high doses, genotoxic effects are not always observed, and 3. the preponderance of the genotoxic effects that have been reported are of the types that probably are of no or negligible genetic significance.”8 The lowest dose of fluoride reported to cause chromosomal changes in mammalian cells was approximately 170 times that normally found in human cells in areas where drinking water was fluoridated at 1.0 mg/L, which indicates a large margin of safety.8 (Note that this would be 242 times greater with fluoridation now set at 0.7 mg/L.) In its subsequent 2006 report,9 the NRC stated after reviewing the evidence available since its 1993 report, that the weight of evidence from studies on rodents indicated a very low probability that fluoride presents a risk of genetic mutation for humans.9 In addition, the 2006 NRC report9 indicated that the results of human studies related to fluoride and its effect on genotoxicity since its 1993 report are inconsistent and do not strongly indicate the presence or absence of genotoxic potential for fluoride. Continued research and evaluation are recommended.9 39. Does fluoride at the levels found in water fluoridation affect human reproduction, fertility or birth rates? Answer. According to the best available scientific evidence, water fluoridation does not have an adverse effect on human reproduction, fertility or birth rates. Fact. In 2011, the European Commission requested the European Scientific Committee on Health and Environmental Risks (SCHER) perform a critical review of fluoridating agents of drinking water. A portion of that report looked at reproductive issues. The report concluded that there is no new evidence from human studies indicating that fluoride in drinking water influences male and female reproductive capacity.20 In its 2006 report,9 the National Research Council (NRC) indicated that since 1990, the quality and number of reproductive and developmental studies using laboratory animals have improved significantly. These high-quality studies indicate adverse reproductive and developmental effects occur only at levels of fluoride much higher than 4 mg/L.9 The NRC also indicated that a few studies conducted with human populations have suggested that fluoride might be associated with alterations in reproductive hormones and fertility. However, the report continued on to explain that limitations in study design, such as the lack of control of reproductive variables, make these studies of little value for risk evaluation.9 A study examining the relative risk of stillbirths and congenital abnormalities (facial clefts, Down syndrome and neural tube defects) found no evidence that fluoridation had any influence on the rates of congenital abnormalities or stillbirths.141 The study, conducted in 2003, analyzed data from two population based registries to identify all stillbirths and congenital abnormalities occurring in northeastern England between 1989 and 1998 and compared the rates of stillbirths and