Study On The Relationship Between Fluoride Content Of Crops And That Of Soil In Fluorosis Areas Of HengYang City

ObjectiveTo Investigate the fluoride content of crops and soil in Hengyang city of different dental fluorosis prevalenvce, to explore the relationship between fluoride content of crops and soil, and to provide a scientific basis for the prevention of endemic fluorosis.MethodsThree villages were randomly sampled from DaoZi town and DaHe town in endemic area of LeiYang city and DaiYingLing town that was non-endemic fluorosis area of ZhengXiang district. The incidence of dental fluorosis of children aged 10-12 year in Grade 4-6 of every school in each village was investigated. Residents around the schools in three groups were sampled. and drinking water, air, food (rice, fresh pepper, baked chili, air-dried chilli, chrysanthemum,chinese cabbage, spinach, beetroot, sweet potato, ternip, green onion,garlic,etc.), paddy soil, vegetable sol, coal, honeycomb briquet, clay mixed with coal were collected. The fluoride content of samples was tested with the fluoride ion selective electrode. Chi square test was performed to judge whether there was significant difference in the prevalence of dental fluorosis among groups. The fluoride content of samples amoung three groups was compared with the single-factor analysis of variance, two groups were compared with the LSD method and correlation of fluoride content between different samples was analyzed by Pearson correlation.ResultsThere was statistically significant difference between the incidence of dental fluorosis in children among three groups (χ2=100.92, P<0.01). The incidence of dental fluorosis in endemic area was higher than that in non-endemic area. There was no statistically significant difference between the fluoride content of drinking water among three groups (F=0.89, P>0.05), and the fluoride content of all the samples was in the range of the national drinking water standards (1.0 mg/L).The fluoride content of indoor air in endemic area groups was higher than that of non-endemic area group,and the difference was statistically significant (F=6.94, P<0.01), Difference of fluoride content of outdoor air was not statistically significant among three group (F=2.31, P>0.05), The air fluoride levels of outdoor were below the allowable limits of national air quality standards (<7μg/m3).There was no statistically significant difference between the fluoride content of coal amoung three groups (F=1.98, P>0.05), but there was statistically significant difference in honeycomb briquet and clay mixed with coal amoung three groups (F=21.99, P< 0.01; F=110.63, P< 0.01)). The fluoride content of honeycomb briquet and clay mixed with coal in endemic area was higher than that in the non-endemic area. There was positive correlation between the fluoride content of clay mixed with coal and honeycomb briquet, indoor air and honeycomb briquet, clay mixed with coal and indoor air amoung three groups(r=0.68, P<0.01; r=0.46, P<0.01; r=0.39, P< 0.05). but there was no statistically significant difference between the fluoride content of coal and clay mixed with coal, coal and honeycomb briquet, coal and indoor air and honeycomb briquet, clay mixed with coal and indoor air amoung three groups (P>0.05)There were statistically significant differences in full-fluoride, water-soluble fluoride content of paddy soil and vegetable soil amoung three groups (full-fluoride:Fpaddy soil=15.54, P<0.01, Fvegetable soil=7.22, P<0.01;water-soluble fluoride:Fpaddy soil=11.49, P<0.01, Fvegetable soil=13.05, P<0.01). The fluoride content of cultivation soil in endemic area was higher than that in the non-endemic area.There were statistically significant differences in the fluoride contents of baked chili,air-dried chilli, fresh pepper, rice,spinach, beetroot,Chinese cabbage,chrysanthemum, green onion.garlic amoung three groups (P<0.05), and the fluoride content in endemic areas was higher than the non-endemic area. There was no statistically correlation between the fluoride content of baked chilli and that of air-dried chilli (P>0.05), but there was positive correlation between the fluoride content of air-dried chilli and that of fresh pepper (r=0.85, P <0.01). There was positive correlation between the fluoride content of baked chili and indoor air, baked chilli and clay mixed with coal, baked chilli and honeycomb briquet (r=0.54, P< 0.05; r=0.58,P<0.01; r=0.39, P<0.05).There was no statistically correlation between the fluoride content of rice and the full fluoride content of paddy soil (r=0.65, P<0.05), but there was positive correlation between the fluoride content of rice and that of the water-soluble fluoride content of paddy soil. There was no correlation between the fluoride content of vegetables and the full fluoride content of vegetable soil (P>0.05), but the fluoride content of vegetables was positively correlated with water-soluble fluoride content of vegetables soil(P<0.05).Conclusion1.The fluoride content of fresh crops in coal-burning endemic area is higher than that of the non-endemic area, Ingesting fluoride from crops is an important way intaking fluoride in endemic area.2.Fluoride content of crops in endemic area is influenced by the water-soluble fluoride content of the cultivation soil.3.Indoor air fluoride in Leiyang city is from clay mixed with coal. The main reason that the fluoride content of baked chili is baking chili by using coal.