For thousands of years, Tibetans have been drinking butter tea to help them digest meat and stay warm in the harsh climate. Tibetan soil has a high fluorine content, which is absorbed by the tea bushes.
Chinese scholars noticed the high levels of fluorine in Tibetan butter tea in 1983 and launched a field study in 1994.
Tzuchi listed fluorine poisoning by tea as one of its overseas relief projects in 2000.
In 2004, Tzuchi and Chinese scholars launched a joint research project which discovered fluorine poisoning from butter tea among minority ethnic groups in Inner Mongolia, Tibet, Sichuan, Qinghai, Gansu and Xinjiang.
According to Tzuchi's study, Tibetans drink large amounts of butter tea, sometimes up to 40-50 cups a day.
"They drink it like water, so it causes many health problems, like dental or skeletal fluorosis, yellow teeth, teeth decay and the stooping of the back," Tzuchi's Wang said.
A separate study by Chinese doctors showed that 53.5 per cent of students in Naqu, northern Tibet, suffer from dental fluorosis due to drinking butter tea from an early age.
According to the World Health Organization, a safe fluorine intake is 2 milligrammes for a child and 4mg for an adult, but the fluorine in a kettle of butter tea (2,600 cubic centimetres from 100 grams of tea) made from the traditional Tibetan brick-tea is 6-10 mg.
The fluorine content in the low-fluorine tea brick is less than 4mg.
Professor Cao Xing from China's Central South University, who headed the research, has obtained the patent for the low-fluorine tea brick and wants to share it with Tzuchi.
But Tzuchi hopes Cao can pass the patent to China's health authorities so that they can mass produce low-fluorine tea bricks for Tibetans and other Chinese ethnic minorities.