Fluoride Exposure During Pregnancy and Its Effects on Childhood Neurobehavior: A Study Among Mother-Child Pairs from Mexico City, Mexico.

Abstract

Artificial fluoridation, implemented worldwide to reduce periodontal diseases, was deemed one of the top public health achievements of the 20th century. In recent years, expert reviews by the US National Research Council (NRC) and the World Health Organization (WHO) have concluded children living in high-fluorosis areas may suffer from cognitive declines. However, exposure measures and statistical methods in past studies have been challenged, and, thus, the true relationship between fluoride exposure and cognition remains unclear. In addition, little is known about fluoride exposure during pregnancy. The objective of this dissertation is to improve understanding of fluoride exposures during pregnancy and to assess whether prenatal and concurrent fluoride exposure is associated with neurobehavioral effects in offspring. The research aims are conducted by using resources from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) study, and a follow-up study called Cholesterol. Chapter 2 is the first population-based study to provide an exposure profile of fluoride during early, mid and late pregnancy, using two different biomarkers, and it is the first to examine whether some periods of pregnancy may be more vulnerable to exposure. Chapter 3 assesses the neurobehavioral effects of prenatal fluoride exposure on the Mental Development Index (MDI) of the children when they are one, two, and three years old. Chapter 4 of this dissertation measures urinary fluoride in children at 6-15 years and examines its association to the total score from the Wechsler Abbreviated Scales of Intelligence Test (WASI.) This work increases our understanding of prenatal and concurrent fluoride exposure and their effects on cognition in children. During pregnancy, we found that fluoride levels do not change as pregnancy progresses once you adjust for other factors, and children of older mothers may be more susceptible to fluoride exposure. We additionally found that maternal fluoride exposure levels did not have any measurable effects on cognition in early childhood in this cohort. We found that concurrent fluoride exposure in males, but not females, aged 6-15 years, was significantly associated with WASI, and this highlights the need for future research considering gender differences in neurocognitive outcomes using longitudinal data.