Beijing is stepping up efforts to reduce illegal barbeques, to cut down on roadside air and noise pollution.

May is the peak time for outdoor grill cooking, which takes a heavy toll on air quality, traffic and residents, said Dang Xuefeng, spokesman for the capital's bureau of city administration and law enforcement.

The smoke from outdoor barbeques is high in fine particulate matter concentration, which poses a severe threat to residents. [File photo]

"As the weather warms up, the streets gradually fill up with roadside barbecue spots, sizzling kebabs on the grill and cold beer, which also create serious air pollution and undesired noise for the neighborhoods," he said.

In addition to sanitation concerns, the smoke from outdoor barbeques is high in fine particulate matter concentration, which poses a severe threat to residents, especially those with heart and lung problems, Dang said. Downtown is the most severely afflicted area, he said, adding that most outdoor barbecues are illegal.

Pan Xiaochuan, a professor at Peking University's School of Public Health, said the smoke from barbeques is a very common source of PM2.5, or particulate matter with a diameter smaller than 2.5 micrometers, and poses a serious threat to people's respiratory systems.

He also suggested that residents are easily irritated by barbeque smoke close to their windows.

Operators of illegal barbeques face fines of up to 5,000 yuan ($813) and may have their facilities confiscated, authorities said.

The city administration office steps up inspections on illegal roadside barbecues every May, and residents can file noise and pollution complaints by dialing 96310.

The city's environmental protection bureau began regulating illegal outdoor barbeques in 2000, but controlling the problem has been difficult.