Chinese scientists have found corn and chili that easily absorb fluoride in the air are more likely to blame for the high incidence of fluoride poisoning in the country's southwestern region.

"Fluorosis, or overexposure to fluoride, is more a result of the local people's eating habit and climate conditions," said Zheng Baoshan, a researcher with the Institute of Geochemistry under the Chinese Academy of Sciences, in southwest China's Guizhou Province Tuesday.

The hypothesis is contradictory to the traditional belief that fluoride poisoning is caused by coal that is used by many Chinese households for cooking and heating.

Zheng said excessive intake of corn and chili, a major diet for people in the southwest, is largely to blame for fluoride poisoning in the southwestern regions. "The more water the food contains, the faster it absorbs fluoride."

According to Zheng, corn and chili easily absorb fluoride in the air and in the humid southwestern regions, people often dry the food by fire lest it goes moldy. "The food absorbs even more fluoride in the drying process," he added.

Zheng and his colleagues also found the sticky clay that is used to bond the powdered coal in the southwest contains 10 times as much fluoride as the coal itself.

"Even if the clay content of the coal is only 20 percent, it gives off at least twice as much fluoride when it is burned," he said.

Fluoride poisoning causes tooth staining and corrosion. In its most severe form, it can cause paralysis.

At the end of 2003, the most recent time that data is available, 67.91 million Chinese were threatened by fluoride poisoning, according to Ministry of Health statistics.

(Xinhua News Agency June 29, 2005)