Abstract
The intelligence was measured of 907 children aged 8-13 years living in areas which differed in the amount of fluoride present in the environment. The Intelligence Quotient (IQ) of children living in areas with a medium or severe prevalence of fluorosis was lower than that of children living in areas with only slight fluorosls or no fluorosis. The development of intelligence appeared to be adversely affected by fluoride in the areas with a medium or severe prevalence of fluorosis but to a minor extent only in areas with only a slight prevalence of fluorosis. A high fluoride intake was associated with a lower intelligence. No correlation was found between age and intelligence in the areas with a medium and severe prevalence of fluorosis. The effect of exposure to a high level of fluoride on intelligence may occur at an early stage of development of the embryo and infant when the differentation of brain nerve cells is occurring and development is most rapid.
Keywords: Child; China; Fluoride; Fluorosis; Intelligence; Intelligence testing.
…Materials and Methods
The survey was carried out in November and December 1991 in the Anshu and Zhijin counties in Guithou Province. The prevalence of fluorosis due to soot from coal burning varied from being absent to being present to a slight, medium or severe degree. In the medium and severe fluorosis areas, it was customary for coal to be used as a domestic fuel for cooking, heating and drying grain whereas in the areas without or only slight fluorosis there was no custom of drying grain by the use of coal.Th e standards of material and cultural life for the children were similar in all four areas. The survey areas have no iodine deficiency disease.
The children surveyed were of Han nationality and numbered 907 with ages from 8-13 years. Children whose intelligence had been affected by congenital or acquired diseases not related to fluoride were excluded. Intelligencc was measured using the China Rui Wen’s Scaler for Rural Areas. In each area, 20-24 children were examined, by a special examiner, in each age group with the groups being sepatated by intervals of six months age.
Results
The numbers of children examined in each area and their mean IQs are shown. The distribution of the IQ scores is shown in Table 3. As shown in Table 3, more children with IQs af <70 and 70-79 and fewer children with IQs of 90-109 and 1 10-119 were present in the medium and severe fluorosis areas than in the slight fluorosis and non-fluorosis areas. No children with IQs of 120-129 and >129 were found in the medium and severe fluorosis areas. In Table 4 the IQs of children of different ages from areas with different
prevalances of fluorosis are shown. A comparison of the IQs of boys and girls is shown in Table 5.
Discussion
The results of the s u n q show that the intelligence, as measured by the mean IQ, of children aged 8- 13 years living in areas with a medium or severe prevalence of fluorosis was lower than that of children living in areas with a slight prevalence of fluorosis or no fluorosis. Similarly more children with a low or borderline IQ were present in the medium and severe fluorosis areas. Similarly more children with a low or borderline IQ were present in the medium and severe fluorosis areas. That a high fluoride environment can adversely the development of intelligence in children is in agreanent with the findings of Guo et al.1 No significant difference in intelligence was present between children in the slight fluorosis and the non-fluorosis areas. The lowering of intelligence in the moderate and severe fluorosis areas indicates that the central nervous systems of the children in those areas are adversely affectcd by fluoride…