Research carried out by 20 different countries has shown that there is a definite link between levels of fluoride in the body and one's IQ levels. The Chinese Xiang research team concluded in 2003 that fluoride levels of 1.9 parts per million will definitely retard the development of one's IQ. A different team in Ding found more recently in 2011 that children who regularly drunk water containing fluoride levels of as little as 0.