| Objective:To understand the distribution and water improvement of drinking water fluorosis in the Corps,analyze the spatial distribution characteristics of fluoride content in drinking water and the prevalence of dental fluorosis in children aged 8 to 12 years,evaluate the non-carcinogenic health risk of fluoride on students aged 6 to 24,and provide a scientific basis for developing and refining control measures for drinking water type fluorosis in the Corps.Methods:1.A cross-sectional study was conducted to investigate the water improvement situation and fluoride content in drinking water fluorosis areas of the Corps in 2019.The median and range(minimum and maximum values)were used to describe the fluoride content,and theχ~2test was used to compare the differences in fluoride qualification rates among different regions.A bilateral test was used to test the level of fluoride contentα=0.05.Draw the spatial distribution of fluoride content in the drinking water of the Corps,and use spatial autocorrelation to reflect its degree of correlation in space.2.ALL children aged 8～12 born and residing in drinking water fluorosis endemic areas and studying in local schools were selected as the research subjects(with a detection rate of no less than 90%).Diagnostic criteria(WS/T 208-2011)were used to examine and determine the prevalence of dental fluorosis,calculate the prevalence of dental fluorosis and dental fluorosis index,evaluate its epidemic intensity and severity.Using Sa TScan 10.01 software to analyze the spatial clustering of dental fluorosis cases.3.Use the USEPA health risk assessment model and Monte Carlo simulation method to calculate the hazard coefficient,and use its to assess the non-carcinogenic health risks of fluoride in drinking water faced bystudents aged 6 to 24 in the Corps.The parameters of risk assessment are surveyed using a stratified cluster sampling method.Results:1.There are 62 endemic areas and farms of drinking water fluorosis in the Corps.The water improvement rate of the Corps is 100%,involving 49 water improvement projects.The water improvement projects cover a population of 1044795,and all water improvement projects operate normally.In 2019,the whole Corps monitored a total of 2308 water samples,with fluoride content between 0.01-3.37mg/L,median0.40mg/L,and qualification rate of 96.01%.The qualified rate of fluoride was 92.07%in the inpatient area and 99.29%in the non-inpatient area.The difference of qualified rate was statistically significant(χ~2=77.778,P<0.001),the qualified rate of water fluoride in the sick area is lower than that in the non-sick area;The difference of qualified rate of fluoride in different water supply modes is statistically significant(χ~2=14.858,P<0.001),which is disinfection only(100%)>conventional treatment(98.58%)>untreated(95.48%)>sedimentation and filtration(94.64%);The difference of qualified rate of fluoride in different divisions is statistically significant(χ~2=126.377,P<0.001),the second division,the sixth division and the twelfth division have the highest qualified rate of fluoride,all of which are 100.00%,followed by 99.29%of the thirteenth division,98.00%of the third division,and 82.20%of the eighth division.2.In 2019,we examined 42839 children aged 8-12 years and 1564 children were detected to have dental fluorosis,including 345(22.06%)very mild,1052(67.26%)mild,144(9.21%)moderate,and 23(1.47%)severe,with a prevalence of dental fluorosis of 3.65%and a dental fluorosis index of 0.07 without dental fluorosis.The prevalence of dental fluorosis among children in teams of each disease area of the regiment ranged from 0 to 22.85%,all of whom had met the national standards for control of endemic fluorosis disease areas with drinking water,and the prevalence of dental fluorosis among children in teams of the first three of the regiments was,in order,48 Regiment(22.85%),Xin Hu Farm(18.01%),8 Regiment(15.93%),and 8 and 48 Regiment(0.40)and 0.56,respectively,which were in marginal prevalence.There was no significant difference in the prevalence of dental fluorosis between males and females(χ~2=0.631,P=0.557);The prevalence of dental fluorosis tended to increase with age(χ~2=21.177,P<0.001).The prevalence of dental fluorosis among children in the Corps showed a downward trend from 2011 to 2019.3.The cases of child fluorosis in the Corps were mainly distributed among the first,third,and fourteenth divisions at the edge of Tarim Basin in South Xinjiang,and the sixth and eighth divisions at the edge of Junggar Basin in North Xinjiang.Sa TScan analysis of child dental fluorosis cases detected seven meaningful aggregation areas,and the primary aggregation area was centered at 42 clusters(39.16N,77.07E)with a radius of 201.08 km,including 42 clusters,gamma total field,45 clusters,48 clusters,49clusters,Pima farms,with RR value of 3.43 and LLR value of 254.03(P<0.01).Global autocorrelation analysis of fluoride in the drinking water of the regiment in 2019 was performed,and the Moran’s I indexes were 0.16,with all P values<0.05,and the high cluster type was mainly distributed among seven and eight divisions.4.Deterministic risk assessment the mean values of the hazard coefficients for non-carcinogenic health risks of fluoride for the group of children aged 6～12 years,the group of adolescents aged 13～17 years,and the group of adults aged 18～24 years were 0.2541,0.1976,and 0.2326,respectively;The hazard coefficient first decreases and then increases with age.The hazard coefficient of women in children and adult groups is slightly higher than that of men,and that of men in adolescent groups is higher than that of women.The hazard coefficient of all age groups is less than 1.The health risk of fluoride non-carcinogenic is low.Monte Carlo based risk assessment:the mean values of hazard coefficients for non-carcinogenic health risks of fluoride for the groups of 6～12 year olds,13～17 year olds,18～24 year olds were 0.29,0.21,0.25,respectively,and the probability of hazard coefficients greater than 1 for the group:children(2.93%)>adults(1.32%)>adolescents(0.93%).Conclusion:1.The drinking water fluorosis endemic area has a high water improvement rate in the Corps.The prevalence of children’s dental fluorosis has reached the national control standard.The effect of water improvement and disease prevention in the endemic area is remarkable,but there are still some areas where the water fluoride exceeds the standard.It is still necessary to strengthen the supervision of the water improvement project and the monitoring of the water fluoride content,as well as the education and publicity of the residents,so as to improve the disease prevention awareness of the residents.2.The noncarcinogenic health risks of fluoride to students aged 6～24 years in the regiment are low,but a few group fields and the agricultural pastoralist team still have exceedances for fluoride,and there are uncertainties in the risk assessment that still need to be focused on noncanonical phase damage from fluoride exceedances. |
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