Fluoride in the urine of pregnant American women has been linked to the risk of neuropsychiatric developmental disorders in children
A prospective cohort study by US scientists has found an association between fluoride exposure during pregnancy and impaired neuropsychiatric development in children. As reported in JAMA Network Open, this study is particularly relevant to populations living in regions where tap water is actively fluoridated.
Fluoride compounds are often added to tap water for population-based caries prevention. The World Health Organisation recommends that the fluoride concentration in drinking water should not exceed 1.5 milligrams per litre, while a target concentration of 0.7 milligrams per litre is considered the optimal fluoridation level. Fluoride can also enter water from soil and rocks or from industrial processes.
It is widely believed that exposure to high levels of fluoride can adversely affect the development of the nervous system. However, recent studies in Mexico and Canada suggest that exposure to fluoride at lower levels common in the United States may also be associated with impaired nervous system development. A recent systematic review by the National Toxicology Programme reported that "it can be stated with moderate confidence that elevated fluoride levels are consistently associated with lower IQ in children." However, fluoride concentrations in drinking water vary from country to country, making it difficult to scale the findings of individual studies.
A research team led by Ashley Malin at the University of Florida first examined the association of prenatal fluoride exposure on children's neurobehavioural performance in the US. The study included 229 mother-child pairs and the children were followed until the age of three. Single urine samples were collected from participants during the third trimester of pregnancy between 2017 and 2020, in which fluoride content, recognised as a reliable estimate of total fluoride intake, was measured.
Analysis showed that a one percentage point increase in maternal urine fluoride concentration (approximately 0.68 milligrams per litre) was associated with a 13.54 percent (p = 0.02) increase in Emotional Reactivity Scale score and a 19.6 percent (p = 0.001) increase in Somatic Complaints Scale score in children. In addition, a one percentage point increase in fluoride was found to be associated with an 11.29 per cent (p = 0.045) increase in children's anxiety scale score and an 18.53 per cent (p = 0.009) increase in autism spectrum disorder scale score. Notably, the patterns found were observed throughout the pregnancy.
Although water fluoridation levels in the United States are considered average, even at these levels there is a risk of neuropsychiatric developmental disorders in children with increased maternal fluoride intake during pregnancy. Larger studies in different countries are needed to increase the amount of evidence on the association between prenatal fluoride exposure and fetal developmental disorders.