The harm of long-term intake of excessive fluoride on the human skeletal system has been proved. There are also reports about the effects of high fluoride on the human nervous system and mental development [1, 2]. Some studies have proved that if the mother has taken in an excessively high amount of fluoride, she can transmit that through the placenta to the fetus . Fluorosis has certain effects on the mental development of children. However, how this high level of fluoride can influence the mental development of children has yet to be reported. In May of 1991, we did some investigation and hereby report the results as follows.
DISCUSSION: The results show that the level of intelligence of primary and secondary students from the high fluoride area and that of primary and secondary students from the non-high fluoride area had very significant differences, proving that high fluoride has adverse effects on the mental development of students. The higher the water fluoride is, the lower the level of IQ. Before 6 years of age is a critical period for children’s mental development, and it is meaningful to choose students older than 7 years old as subjects. Although intelligence is influenced by many factors, the people of these two areas who were examined are very comparable. The students’ years of education, the size of the primary and secondary schools, and the quality of teaching are very similar. The middle school students of these two areas studied at the same secondary school, and their intelligence had significant differences, mainly caused by water fluoride. These results are basically the same with the results from investigations in other provinces [4, 6]. The regular materials of normal intelligence tests are made according to the testing results of students from urban areas. Therefore, it is not very proper to use the regular standards of IQ classification among the people from remote and rural areas. It is necessary to make corresponding IQ classification standards.