Investigation of drinking water fluoride and fluorosis in Shaanxi Province from 2005 to 2007

Abstract

Objectives To investigate fluoride in drinking waters and fluorosis status and evaluate the effectiveness of fluoride-reducing projects in Shaanxi Province from 2005 to 2007. Methods In the Shaanxi province-wide, the 10 endemic areas of fluorosis were chosen according to historical data as focusing areas for investigation. The village was considered as investigation spot, 5 water samples were collected from each village for investigating of fluoride content. Four water samples were collected from each fluoride-reducing project for evaluating its effectiveness. Fluoride concentrations in drinking water were measured by fluoride-selective electrode method or speetrophotometry. When fluoride content in drinking water was greater than 1.00 mg/L, the epidemical study wasd conducted to investigate fluorosis patients, focusing on investigating of dental fluorosis prevalence in 8 to 12-year-old children and skeletal fluorosis prevalence in adults. Dental fluorosis of children was diagnosed by using Dean's method, and adult skeletal fluorosis was diagnosed according to National Standard for Clinical Diagnosis of Endemic Skeletal Fiuorosis(GB 16396-1996). Results The fluoride content in drinking water from 6390 villages was measured. The fluoride content of drinking water of 2619 villages ranged from 1.0 to<2.0 mg/L, where 1 654 998 people exposed. Additionally, the fluoride content of water of 845 villages ranged from 2.0 to<4.0 mg/L, where 355 623 people exposed. Moreover, the fluoride contents of water of 272 villages exceeded 4.0 mg/L, where 111 466 people exposed. The median of fluoride content in drinking water was 1.15% in the whole province, and fluoride content in drinking water exceeded 1.00 mg/L in Weinan, Xianyang and Yulin where were concentrated distribution areas of high fluoride water. Among 3115 fluoride-reducing projects, the fluoride content of drinking water of 1269 projects ranged from 1.0 to<2.0 mg/L, where 1 415 877 people exposed. Additionally, the fluoride content of drinking water of 120 projects ranged from 2.0 to<4.0 mg/L, where 43 888 people exposed. Moreover, the fluoride content of drinking water of 14 projects exceeded 4.0 mg/L, where 5960 people exposed. The detectable rate of dental fluorosis of 8 to 12 year-old children and skeletal fluorosis of adults reached 37.4%(16 489/44 081) and 5.1%(15 877/310 993), respectively. Conclusions The widely distribution of high-fluoride in drinking water still contributes to the prevalence of fluorosis in Shaanxi Province. The quality of fluoride-reducing projects should be further improved. Key words: Water pollution; Fluorides; Fluorosis, dental; Osteofluorosis