Objective To investigate the incidence of dental fluorosis,urinary fluoride level and intelligence of children who lived in the coal-burning-borne endemic fluorosis areas and to reveal the effects of comprehensive control measures on intelligence of children in this area.
Methods Children aged 8-12 who lived in coal-burning-borne endemic fluorosis areas in Bijie City of Guizhou Province were selected and divided into two groups according to the duration of comprehensive treatments given:long treatment group (Xiaba Village and Zhongtun Village, furnace stove was changed and comprehensive control measure of health education was carried out for more than 3 years) and short treatment group (Chadi Village and Maoliping Village, stoves were improved and health education time < 1 year). The children who lived in a non-fluorosis area were selected as controls in 2012. Dental fluorosis was diagnosed by the method of Dean; urinary fluoride was analyzed by the method of fluoride-ion selective electrode; and the intelligence quotient (IQ) was measured by Raven’s Standard Progressive Matrices Test.
Results The number of children surveyed in control group was 104, long treatment group was 298, short treatment group was 339, and the incidence rates of dental fluorosis were 0 (0/104), 72.5% (216/298) and 85.2% (289/339), respectively, and the incidence rates of dental fluorosis in children lived in the endemic fluorosis areas were significantly increased compared with that of control group; the difference of incidence rates between long treatment group and short treatment group was statistically significantly (x2 =15.736,P < 0.01). Urinary fluoride content were (2.33 ± 0.18) and (3.03 ± 0.16) mg/L, respectively, compared with the control group [(1.34 ± 0.64) mg/L], the values in endemic fluorosis areas were significantly higher (F =306.53,P < 0.01). Above average IQ of children in the control group was 97.1% (101/104), which was significantly higher than that of long and short treatment groups; after a lengthy treatment, mental retardation detection rate was significantly lower in the low-age group, 8-10 year-old children (x2 =7.542,P < 0.01). Urinary fluoride content was negatively correlated with the level of IQ (r =-0.553,P < 0.01).
Conclusions The intelligence development of children in coal-burning-borne endemic fluorosis area is significantly delayed. After a certain period of comprehensive treatment, the decreased level of cognition is inhibited and the mental retardation in the low-age group is improved.