Lung cancer has emerged as the leading killer in rural China, closing to the incidence and mortality of urban men and women stricken with the disease.

"The incidence and mortality of lung cancer has dramatically climbed in China's rural population over the past ten years," says surgical oncology professor Zhou Qinghua. "The rates for each have hit 47.6/100,000 and 39.1/100,000 respectively in 2015."

Lung cancer claimed 66,100 rural lives last year, overtaking breast cancer as the third leading cause of cancer deaths in women in 2015, which killed 25,700 women.

Speaking at the first West China International Conference on Lung Cancer recently held in Chengdu, Sichuan, Zhou noted that esophageal carcinoma that had been blamed for cancer deaths in rural China due to low fruit and fresh vegetable intake from the 1970s to the 1990s.

A well-established surgeon, Zhou receives as many as 1,000 lung cancer patients a year from all over the country, near 50 percent of them are farmers. "The youngest patient I saw was a 13 year old country girl from Sichuan, and a 14 country boy from Yunnan. The oldest one was a 91 year old rural grandpa . "

The old man had smoked most of his life, and his cancer was already in its late stages when detected. "But the 13 and 14 year old didn't smoke at all and had no family history of cancer. I deeply doubted that involuntary smoking and air pollution combined could be responsible," Zhou said.

In fact, Ge Jiu, the young boy's home county, is notorious for tin mining-related pollution that has brought about silicosis deaths affecting a huge number of people. Passive smoke and indoor air pollution are mainly responsible for the incidence of lung cancer in Chinese farmers, especially in those high-risk areas like Xuanwei county of Yunnan.

Dr. Qiao Youlin, an acclaimed epidemiologist of oncology noted that people of Xuanwei have lived in unhealthy conditions for generations. Most are still using firepits or coal ovens for cooking and heating. These release heavy PAHs (polycyclic aromatic hydrocarbons) which creates indoor air pollution

The figures from the National Cancer Center suggested that the incidence and mortality rate of lung cancer in Xuanwei are two times higher than the country's average rate of 53.4/100,000 and 44.4/100,000 in 2015.

This disease is difficult to detect in its early stages, so most lung cancer cases are found during the late stages, said Zhou, who is also the director of Cancer Center & Institute of West China Hospital of Sichuan University.

According to Zhou, the overall 5-year survival rate for lung cancer as of 2015 stands at 16.7 %.

Unlike cervical cancer, caused by the HPV virus, the exact cause of lung cancer is yet unknown, making the disease difficult to curb.

However, certain risk factors for lung cancer, include smoking, exposure to air pollution, radon gas, and genetics, are scientifically known to play a part in causing cells to become cancerous.

About 75 percent of lung cancer cases in men in China are due to long-term tobacco smoking, while 25 percent occurs in men who have never smoked. While most of female lung cancer were not smoke.

In the case of rural China, second-hand smoking and indoor air pollution play a dominate role in lung cancer. In addition to that, Dr. Qiao thinks that a lack of awareness about the effects of tobacco smoking as a leading risk factor for lung cancer puts rural people's health in jeopardy.

He said some people may be nonsmokers, but under pressure of sharing smoking and gifting they become social smokers, joining in a gatherings.

In addition, smoke-free area legislation and policies are not in force in rural China.

In fact, the country does not have yet a national smoke-free law. So far only metropolitans like Beijing and Shanghai have banned smoking in public areas.

As of June 1, 2015, all indoor public places in Beijing are required by law to be 100 percent smoke-free, including indoor workplaces, restaurants and bars, hotels, airports, and public transport facilities.

Despite this, Dr. Qiao thinks that the country's constant promotion of urbanization and industrialization are responsible for increase in the number of farmers suffering lung cancer. He notes "these two ambitions have indeed brought heavy pollution to rural China."

In 2015, lung cancer occurred in 1.8 million people worldwide and claimed 1.6 million lives. And in China, there were 733,300 new cases and about 610, 200 people lost their battles with the disease.

Overall, about 19.5 percent of people in urban China with lung cancer survive five years after the diagnosis. Outcomes are depressingly lower in rural areas, where only about 11.2 percent survive for the same five years.

According to Dr. Qiao, a recent trend analysis shows the incidence of lung cancer in China has increased over the last 20 years and it is predicted that the disease burden will continue if no effective action taken to keep the disease at bay.