1986年,一个社区的供水系统发生意外事故,由于疏忽大意造成阀门松开,从而使水中灌入过量的氟硅酸。水的酸化作用致使氟化物含量高达51％,含铜量增至百万分之25～41。几天后,对该地居民进行挨家挨户调查,从这个社区68％的家庭成员收集资料, In 1986, an accident in the water supply system of a community caused the valve to loosen due to carelessness, so that excessive amounts of fluosilicate were poured into the water. Acidification of water leads to a fluoride content of up to 51% and a copper content of 25 to 41 ppm. A few days later, residents of the area were surveyed door-to-door, collecting information from 68% of family members in the community,