AADR Comment on “Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico” by Bashash, M. et al. in Environmental Health Perspectives published online September 19, 2017
The findings reported by Bashash et al. add to the scientific literature on associations between fluoride exposure and cognitive outcomes. Their epidemiologic study using 299 mother-child pairs in Mexico examined maternal urinary fluoride levels, as a proxy measure of pre-natal fluoride exposure, and two measures of cognitive outcomes in their children at age 4 and 6 -12 years. Their findings must be taken into context with previous studies, including the New Zealand Dunedin longitudinal study that did not find an association between fluoridated water and IQ.
It is also important to note that Bashash et al. used data from a longitudinal birth cohort study in Mexico (ELEMENT) originally designed to examine how environmental exposures to metals and other chemicals affect pregnant women and children, and not to examine the specific relationship between fluoride exposure and cognitive development. The current study is examining samples of urine from two cohorts, the first to investigate prenatal lead exposure (1997-2001) and the second, the effect of calcium supplementation (2001-2006). As an examination of fluoride was not part of the original study design, there are no data on total fluoride intake by the pregnant mothers or their children, other than the fact that Mexico does not have community water fluoridation. Exposure to fluoride would be from naturally occurring in water supplies, fluoridated salt, and other dietary and environmental sources.
Some places in Mexico with high concentrations of naturally-occurring fluoride in water also have high concentrations of arsenic, a known neurotoxin. As the authors noted, information regarding the study population’s exposure to arsenic or other environmental toxins was not available, and therefore, could not be ruled out as a confounding variable. Given such lack of exposure data, among other limitations clearly cited by the authors, the results should not alter current policy recommendations on the use of fluorides for caries prevention.
The AADR concurs with Bashash et al. that the ability to extrapolate their findings to how exposures may impact general populations is limited given the lack of data on fluoride exposure and fluoride pharmacokinetics during pregnancy. The authors conclude that their findings must be confirmed in other populations. The AADR agrees with the authors that these findings reinforce the need for additional research.
AADR notes that fluoride has been an important tool in reducing the prevalence of dental caries in the United States. Specifically, the Centers for Disease Control and Prevention named community water fluoridation one of the top 10 public health achievements of the 20th century. Other fluoride interventions include the application of topical fluorides including fluoride varnish, the use of fluoride supplements and fluorides in toothpaste. As a result, caries prevalence in children has been reduced dramatically as has the number of older adults with total tooth loss in the United States.