Cai Wanfa, local canal administration, said, "the main problem is the water level."

Although removal of excessive fluoride from drinking-water may be difficult and expensive, low-cost solutions that can be applied at a local level do exist.

El nino raises the local sea level by a few tens of centimetres, and they believe the extra water weight may increase the pressure of fluids in the pores of the rock beneath the seabed.