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龋齿(蛀牙)是一种多发病,在自来水加氟以前,广州市小学生中百分之七十三的人患有这种病,乳牙和恒牙的龋齿平均每人在三个以上。自一九六五年开始,广州市自来水在原来每升水零点二五毫克天然含氟量的基础上,通过简易设备投加氟硅酸,使每升水的含氟量提高到零点八毫克。每年的代价约相当于每个水人口二分多钱。氟硅酸是磷肥厂从废气中回收的副产品。
Dental caries (tooth decay) is a frequently occurring disease. Prior to adding fluoride to tap water, 73% of pupils in Guangzhou suffered from the disease, with an average of over three teeth per deciduous teeth and permanent teeth. Since 1965, based on the original fluorine content of 0.25 milliliters per liter of water in Guangzhou City, the fluorosilicic acid was added through simple equipment to raise the fluorine content per liter of water to 0.8 milligrams . The annual cost is equivalent to about two points more for each water population. Fluorosilicic acid is a by-product of phosphate fertilizer plants that is recovered from the flue gas.