A cancer hospital in Jiangsu province has denied media reports that an 8-year-old girl became China's youngest lung cancer patient due to worsening air pollution.

After checking its patient database, the Jiangsu Cancer Hospital said the youngest lung cancer patient it has received was a 10-year-old girl in November 2006. The girl recovered after surgery.

The girl had been coughing for more than two months, and doctors found a tumor in her right lung, according to the case record provided by the hospital.

The cause of her lung cancer could not be determined because it was complicated to identify, the hospital wrote in an e-mail to China Daily at the weekend.

This month, China News Service reported that the hospital had recently taken in an 8-year-old lung cancer patient and, citing a doctor named Feng Dongjie at the hospital, the article suggested that smog could be the direct cause of the disease.

The news received wide media attention, with news reports saying in the past week that worsening air pollution was linked to the illness of China's youngest lung cancer patient.

Feng, the doctor, said in an e-mail to China Daily: "Many factors contribute to lung cancer, such as smoking, ionizing radiation, genetic factors and air pollution. Over-fatigue and staying up all night also contribute.

"It's true that air pollution can harm human health, but to what extent is still being researched. Lung cancer is a disease that can be caused by multiple factors, so we cannot draw a conclusion that tiny particles in the air are the direct reason for the disease."

Air pollution is known to cause heart and lung diseases, but new evidence shows that it may also cause cancer, according to the World Health Organization.

Experts suggested paying more attention to the possible harm smog might do to children.

"Children are more likely to be influenced by air pollution than adults because of their vulnerable physiology, but it's extremely rare to see such a young child diagnosed with lung cancer," said Kan Haidong, a professor from the School of Public Health at Fudan University, who has long been working on studies on the link between environmental factors and health.

Kan added that people should be cautious in making a direct connection between air pollution and a patient's cancer.

"It usually takes five to 10 years for a person to go from being exposed to a cancer-causing environment to being diagnosed with cancer. In this regard, there is less possibility for the girl to develop lung cancer from external environmental factors," Kan said.

Kan also said that hereditary and genetic factors may have contributed to the girl's condition.

According to the American Cancer Society, lung cancer is extremely rare among children and occurs mainly in older people. About two out of three people diagnosed with lung cancer are 65 or older, and the average age for diagnosis is about 70.

Kan said smoking is far likelier than environmental factors to cause lung cancer.

In China, smoking, including secondhand smoke, is the primary cause of lung cancer, accounting for more than 80 percent of cases, national health authorities say.