Investigation of fluoride level in drinking water and state of endemic fluorosis in Yan'an city

Objective To investigate the distribution of water-borne fluoride and the current situation of endemic fluorosis in Yan'an city in 2006, and to evaluate the effect of water defluoridation project by improving driking water quality. Method In 2006 in Yan'an city, 5 samples from water source were collected in each selected village that was chosen according to 5 directions of East, West, South, North, and Central. Meanwhile, 1 sample from water source, 1 sample from water processing factory and 2 tap water samples were collected from each water defluoridation project. Water fluoride was determined by spectrophotometric method, teeth and skeletal fluorosis examination were performed by Dean method and "national criteria of endemic skeletal fluorosis diagnosis of China" in children aged 8-12 year and adults, respectively if water fluoride level > 1.00 mg/L Results Of 726 water samples from 293 villages tested, samples from 25 villages had higher fluoride( > 1.00 mg/L), and these villages covered a population of 11 610 people and most of these people were in Wuqi and Yanchuan counties. Water fluoride ranged from 0.10 mg/L to 3.50 mg/L, with median being 0.59 mg/L. Of 100 water samples from 25 water defluoridation projects, only 1 sample exceeded the national criteria in Yanchuan, and Wuqi counties, respectively,with fluoride level being 1.85 mg/L and 1.60 mg/L, respectively, and population exposed was 3083 and 708, respectively, with water fluoride ranged 0.30 - 2.00 mg/L In the examination of 1281 children aged 8 - 12, we detected 238 cases of dental fluorosis, and the detection rate reached 18.58%; 13 900 adults were checked, and 375 cases were confirmed of skeletal fluorosis, a detection rate reached 2.70%. Conclusions Yan'an has a wide range of water with high fluoride and severe fluorosis people. The water defluoridation projects need to be further improved. The task of prevention of endemic fluorosis is still arduous, and we should speed up the implementation of comprehensive water defluoridation measures. Key words: Drinking; Fluorides; Fluorosis, dental; Osteofluorosis