BACKGROUND: Mexico is included in the list of countries with concurrent arsenic and fluoride contamination in drinking water. Most of the studies have been carried out in the adult population and very few in the child population. Urinary arsenic and urinary fluoride levels have been accepted as good biomarkers of exposure dose. The Biomonitoring Equivalents (BE) values are useful tools for health assessment using human biomonitoring data in relation to the exposure guidance values, but BE information for children is limited.
METHODS: We conducted a systematic review of the reported levels of arsenic and fluoride in drinking water, urinary quantification of speciated arsenic (inorganic arsenic and its methylated metabolites), and urinary fluoride levels in child populations. For BE values, urinary arsenic and fluoride concentrations reported in Mexican child populations were revised discussing the influence of factors such as diet, use of dental products, sex, and metabolism.
RESULTS: Approximately 0.5 and 6 million Mexican children up to 14 years of age drink water with arsenic levels over 10 ?g/L and fluoride over 1.5 mg/L, respectively. Moreover, 40% of localities with arsenic levels higher than 10 ?g/L also present concurrent fluoride exposure higher than 1.5 mgF/L. BE values based in urinary arsenic of 15 ?g/L and urinary fluoride of 1.2 mg/L for the environmentally exposed child population are suggested.
CONCLUSIONS: An actual risk map of Mexican children exposed to high levels of arsenic, fluoride, and both arsenic and fluoride in drinking water was generated. Mexican normativity for maximum contaminant level for arsenic and fluoride in drinking water should be adjusted and enforced to preserve health. BE should be used in child populations to investigate exposure.
Fluoride toothpaste use has been one of the most common strategies to prevent dental caries in Mexico and worldwide. Studies have reported that between 49.8% to 90.9% of children 6 to 13 years old use fluoride toothpaste at least once a day . Toothpaste fluoride concentrations for children in Mexico varied from nondetectable to 1153 mg/Kg, with an average of 563 ± 350 mg/Kg . These large variations are due in part to the lack of an official regulation and nonmandatory normativity . Children younger than 6, especially those not supervised by an adult, are at higher risk of developing dental fluorosis due to ingesting excessive dental products. Mexican regulations have established the use of a pea-sized portion of toothpaste with 550 mg/Kg of fluoride concentration under adult supervision for children from 2 to 6 years. Excessive quantities and adult toothpaste (1000 mg/Kg of fluoride) use by children under 6 was reported . Moreover, an increase in dental fluorosis associated with ingesting dental products has been reported in Mexican children 11 to 12 years old . It has been estimated that toothpaste can contribute at least 20% of the total fluoride exposure in children .
Given the potential adverse health effects related to arsenic and fluoride, immediate measures should be taken to reduce exposure, particularly for vulnerable populations and specifically for children and pregnant women…