Analysis of surveillance results of drinking-water-born endemic fluorosis in Shaanxi Province from 2009 to 2013

Abstract

Objective To investigate the operating situation of water-improvement projects, fluoride content in drinking water and the tendency of drinking-water-born fluorosis in Shaanxi Province. Methods In the areas of drinking-water-born endemic fluorosis, 15 villages in 5 counties were randomly selected as monitoring sites, by random number table method. Ten water-improvement projects in each county were randomly selected to investigate the operating situation and 1 water sample from the tap water of each water-improvement project was collected to determine the fluoride level in 2009-2011. For water-improvement villages, the operating situation of the water-improvement projects was monitored and 1 water sample from the tap water of each water-improvement project was collected to determine the fluoride level, and for water-unimprovement villages, 1 water sample from each direction of the east, west, south, north and middle of the villages was collected, respectively, to determine fluoride level in 2009-2013. Dental fluorosis of 8-12 years old children and X-ray skeletal fluorosis of adults 25 years old were examined in each village. Water fluoride was tested according to the Standard Testing Methods for Drinking Water (GB/T 5750.5-2006). Diagnosis of dental fluorosis was based on the Dean's Standard (2009 to 2011 edition) and WS/T 208-2011 (2012 to 2013 edition) and that of the adults X-ray skeletal fluorosis was based on WS 192-2008. Results The number of investigated water-improvement projects was 146 in survey counties and 68 in survey villages. The normal operation rates were 97.95% (143/146) and 98.53% (67/68), respectively. The qualified rates of water fluoride were 53.42% (73/146) and 61.67% (42/68), respectively. The populations covered by the qualified water-improvement projects were 18.93% and 8.70% of the total water-improvement projects. And, 78.95% (15/19) of the water-unimproved villages had a water fluoride level of over 1.2 mg/L in the drinking water. In the water-improved villages, children dental fluorosis rate reached an average of 41.62% (1 061/2 549) and decreased year by year from 2009 to 2013 (except 2012) (χ2=46.818, P< 0.01), but in the water-unimproved villages, the rate was 64.73%(1 167/1 803) on average and did not go down year by year, and the difference was statistically significant (χ2=225.557, P< 0.01). Adults X-ray skeletal fluorosis rate was 22.55%(124/550) in the water-improved villages and 30.00% (60/200) in the water- unimproved villages in 2009, and the difference was statistically significant (χ2=4.402, P< 0.05). In 2013, adults X-ray skeletal fluorosis rate was 34.17%(219/641) in the water-improved villages and 24.67%(37/150) in the water- unimproved villages, and the difference was statistically significant (χ2=5.010, P< 0.05). Conclusions The measures of water improvement against fluoride have showed definitely control effects, but excess fluoride in drinking water is still a health problem, and the prevalence of fluorosis is not controlled completely. The control work remains to be further strengthened and deepened. Key words: Drinking; Fluoride poisoning; Data collection