China is expected to have more than 800,000 lung cancer patients diagnosed annually by 2020, with nearly 700,000 people dying from the disease each year, according to the latest forecast by medical experts.

Lung cancer has been a growing problem in China since 2000 due to risk factors such as an aging population, air pollution and smoking. "The rapid increase of the disease will last for at least 20 years," warned Zhi Xiuyi, head of the Lung Cancer Diagnosis and Treatment Center of Capital Medical University, Beijing.

And Zhong Nanshan, a respiratory expert and academic at the Chinese Academy of Engineering, expects that PM2.5, a major cause of smog, will replace smoking as the top risk factor for lung cancer.