ENDEMIC FLUOROSIS IN SAN-LUIS-POTOSI, MEXICO .1. IDENTIFICATION OF RISK-FACTORS ASSOCIATED WITH HUMAN EXPOSURE TO FLUORIDE

In order to identify risk factors associated with human exposure to fl uoride in San Luis Potosi (SLP), Mexico, a biochemical and epidemiolog ical study was carried out in 1992. Results from the analysis of fluor ide sources showed that 61% of tap water samples had fluoride levels a bove the optimal level of 0.7-1.2 ppm. The levels were higher after bo iling. In bottled water, fluoride levels ranged from 0.33 to 6.97 ppm. These sources are important since in SLP 82% of the children drink ta p water, 31% also drink bottled water, 92% prepare their food with tap water, 44% boiled all the drinking water, and 91% used infant formula reconstituted with boiled water. The prevalence and severity of denta l fluorosis in children (11-13 years old) increased as the concentrati on of water fluoride increased. At levels of fluoride in water lower t han 0.7 ppm a prevalence of 69% was found for total dental fluorosis, whereas at levels of fluoride in water higher than 2.0 ppm a prevalenc e of 98% was found. In the same children, fluoride levels in urine wer e quantified. The levels increased as the concentration of water fluor ide increased. Regressional analysis showed an increment of 0.54 ppm ( P < 0.0001) of fluoride in urine for each ppm of fluoride in water. Fl uoride urinary levels were higher in samples collected during the afte rnoon (1800) when compared with sample collected during the morning (1 100). Taking together all these results, three risk factors for human exposure to fluoride in SLP can be identified: ambient temperature, bo iled water, and food preparation with boiled water. These factors expl ain the prevalence of dental fluorosis in SLP. (C) 1995 Academic Press , Inc.