Low-moderate fluoride exposure and intelligence among Chinese school-aged children: Role of circulating mtDNA content

Abstract Mitochondrial DNA (mtDNA) content alterations are potential mediators of neuronal disorders. However, what effects of mtDNA content are on fluoride-induced neurotoxicity remain elusive. Here, a cross-sectional study was conducted to investigate roles of circulating mtDNA content on associations between fluoride and intelligence quotient (IQ) in 605 children aged 7–13 years from Tianjin, China. We assessed IQ and circulating mtDNA content in peripheral blood through the second edition of Combined Raven's Test-The Rural in China (CRT-RC2) and qRT-PCR methods. National standardized ion selective electrode method was used for fluoride concentrations in drinking water samples from each village and urine samples. Our results showed that the median (interquartile range) of water and urinary fluoride concentrations were 1.00 (0.70–2.20) mg/L and 0.41 (0.15–2.29) mg/L respectively. Water/urinary fluoride concentrations were negatively associated with not only IQ scores but mtDNA content, which in turn was positively linked with odds of children having excellent intelligence (P for trend