Fumes let off during cooking at home can be linked with respiratory issues, including cancer, but more research needs to be done to determine the effect on air pollution levels, according to medical and cooking experts.

"It is certain that fumes from cooking, especially frying, can cause irritation to the respiratory tract and may be a partial cause of cancer among some people," said Chen Jingyu, a lung surgeon and vice-president of Wuxi People's Hospital in Jiangsu province.

"But so far, no scientific research has been done to identify cooking fumes as a cause of high PM2.5 levels," he said.

At present, vehicle exhaust emissions, coal combustion and industrial dust remain the biggest sources of PM2.5 pollution, he said.

His words came after Xie Xinyuan, a researcher from Nature University, a nonprofit environmental protection organization in Beijing, conducted a series of experiments on Sunday on PM2.5 levels in a kitchen.

Xie's tests showed frying foods triggered higher levels of PM2.5, compared with boiling and steaming during indoor cooking.

PM2.5 levels rose to about 42 micrograms per cubic meter from 31 micrograms per cubic meter, after Xie boiled corn for 10 minutes, according to the survey. The level of PM2.5 exceeded 272 micrograms per cubic meter when he fried potatoes for five minutes.

The figure bounced up to 787 micrograms per cubic meter when he sauteed ginger, garlic and pepper in cooking oil, according to the survey.

"The PM2.5 monitor was placed in the same location for each experiment in which different cooking techniques were used, and the change in PM2.5 levels was apparent," Xie said.

"Steaming and boiling have a limited effect on human health. While, the harm caused by frying is still uncertain since — besides the increased level of PM2.5 — some carcinogenic substances may also be produced when cooking this way," he said.

Xie's survey again triggered concerns over Chinese traditional cooking methods after Zhao Huimin, director of Beijing's Municipal Foreign Affairs Office, said last week that the amount of emissions from cooking activities contributed considerably to the city's fine particulate matter pollution.

Zhao's words were soon met with harsh queries on the Internet. Authorities from the Beijing Municipal Environmental Protection Bureau later said cooking was not the main cause for the haze over the city.

On Tuesday, a report from the Modern Express newspaper said fumes from cooking Cantonese dishes are limited due to their light, non-greasy flavors, while smoke from Hunan and Sichuan cuisines with stir fries and peppers are always heavy.

But the report did not provide any specific data.

"I don't think such cooking surveys have practical meaning since measures for removing fumes, such as windows and cooking vents, have been ruled out," said a senior cooking expert in Beijing who refused to disclose his name.

Also, the effectiveness of these methods is removing cooking fumes varies in different homes, he said.

Also, frying and barbecuing are known to result in a great loss of nutrients in foods, while steaming and boiling are better, said the cooking expert.

"But since these styles of cooking have been deeply rooted in the Chinese culture for a long time, people cannot easily change to begin considering these health effects," he said.

jinzhu@chinadaily.com.cn