To explore the relationship between children's intelligence and urinary fluoride in Suojia Township of Miao, Yi and Hui Nationalities (referred to as Suojia Township), a coal-burning-borne endemic fluorosis area in Guizhou Province.

In April 2019, 173 children aged 10 to 13 years old were selected from three schools in Suojia Township. According to whether they had dental fluorosis, the children were divided into case group (n = 104) and control group (n = 69). Middle segment urine samples of the children were collected and urinary fluoride level was determined by the method of ion-selective electrode. Combined Raven's Test-the Rural in China (CRT-RC2) was used for children's intelligence quotient (IQ) test. Linear regression analysis was used to observe the association between urinary fluoride and IQ, and the results were expressed by regression coefficient (β) and 95% confidence interval (CI).

Urinary fluoride level of case group was higher than that of control group [(2.14 ± 1.78) vs (1.53 ± 0.98) mg/L], and IQ was lower than that of control group [(92.33 ± 11.68) vs (100.38 ± 11.87) points], and the differences were statistically significant (t = 2.58, 4.41, P < 0.05). The linear regression equation of urinary fluoride (X) and IQ (Y) of case group was Y = 96.99 - 2.86X. For every 1 mg/L increase in urinary fluoride level, IQ decreased by 2.86 points (β = - 2.86, 95%CI: - 5.48 - - 0.24).

Long-term exposure to fluoride pollution from coal burning may damage children's intelligence, and children's IQ decreases with increase of fluoride level in urine.

Fluorine; Child; Urine; Intelligence quotient