SHANGHAI - With the visitors, comes the garbage.

The large number of visitors to Expo 2010 Shanghai are bringing traffic pressure, long lines at many pavilions, and also more waste.

An average of 160,000 visitors a day during the first five days of the Expo's operation created nearly 200 tons of waste each day, Zhang Quan, director of the Shanghai Environmental Protection Bureau, said on Wednesday.

Although organizers were quick to address the higher-than-expected amount of waste by increasing garbage bins and sanitation staff, visitors' voluntary separation of wastes would be highly helpful in achieving a more efficient collection and treatment of waste, Zhang said.

"We need concerted efforts from both the organizers and visitors for a better environment at the Expo. If everyone can do their job, it'll be much easier for the workers to do their part," said Zhang, adding that Expo authorities are considering adding additional staff to guide visitors when they dump waste.

Expo organizers have been trying to promote waste separation by installing separated bins for different types of wastes. However, the idea has been poorly received by the visitors and not many people have actually paid attention to this, authorities said.

Also, not many visitors have noticed the seedling-shaped garbage bins within the Expo Garden that are air-pumped and can transport waste directly to disposal plants using an underground transportation system.

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The system, stretching over 4,000 meters and covering part of the Expo Garden, boasts a clean collection of waste and reduces traffic congestion as it does not need ground transportation. But according to Zhang, its use had been quite limited in the past few days.

Zhang Xuefeng, a visitor from Zhejiang province, said he had not heard of the air transportation system and urged organizers to do a better job of informing people about it.

Air quality is also closely followed in the Expo Garden, which so far has been rated as "fair" for the past five days.

Zhang said the city has developed a cooperation mechanism with neighboring Zhejiang and Jiangsu provinces so that if air quality in the region falls close to the bottom of the standard, emergency measures will be carried out, including ordering power plants to use coal with a lower content of sulfur.

Zhang also said earlier that enterprises within 300 km of Shanghai in the Yangtze River Delta would be subject to production control during the six-month event if the city's air quality falls below standards.