BEIJING, May 14 (Xinhua) -- Chinese researchers have found that using solid fuel for cooking and heating may generate a large amount of pollutants that can increase the risk of cardiovascular and all-cause mortality.

The research was based on a seven-year study (2008-2014) involving 270,000 rural residents in Sichuan, Gansu, Henan, Zhejiang, and Hunan provinces. The average age of participants was 51, and 59 percent were women.

Researchers found that people using solid fuel for cooking, including wood, coal, crop and animal waste, had greater risks of cardiovascular mortality, increasing by 20 percent, with all-cause mortality increasing by 11 percent, compared to those using clean fuels, such as gas and electricity.

All-cause mortality among users of solid fuel for heating increased by 14 percent, and their chances of cardiovascular death increased by 29 percent. The longer the use of solid fuel, the greater the risk of death.

The risk was lower among those who had previously switched to clean fuels and those who used ventilated cooking stoves.

The research, led by Wu Tangchun from Huazhong University of Science and Technology, and Li Liming from Peking University, was published last month in the Journal of the American Medical Association.