Most of the 211 workers who inhaled zinc fumes while working underground building a tunnel on Monday have already resumed work, according to one source.

"Three workers are being treated in hospital," said Xu Xiangsheng, Party secretary in the Administration Office of the Fuxing Donglu Tunnel Engineering Project.

The 2,785-metre-long tunnel is the first double-deck tunnel in the country and the fifth tunnel to cross the Huangpu River.

On Monday, Zhou Junda and his 12-member team went to work as usual.

Zhou said that by lunchtime his throat was on fire and he felt dizzy, but ignored it.

When he returned to work in the afternoon, he felt worse and found his co-workers were suffering like him.

"At about 4:00 pm, we realized things were serious and that there must have been something wrong down there," Xu said.

By 5:30 pm, leaders of the project company evacuated all workers and sent anyone feeling ill to hospital.

In all, 211 workers were sent to Shanghai No 1 and 2 hospitals, Huangpu District Central Hospital, Shanghai East Hospital and Renji Hospital.

Common symptoms were fever, choking and headaches. In Shanghai East Hospital, a shattered Zhou had a temperature of 39 degrees.

Most of the workers have improved after being given fluids, oxygen and allergy treatment.

They were back at work the next morning.

The cause of the problem was zinc that had been painted on steel sheets in the pump cabin in the tunnel, according to on-the-spot investigators from the Shanghai Municipal Sanitary and Anti-Epidemic Supervision Authorities.

Work with the zinc was completed on Monday morning and it was the excessive density of fumes in the air that poisoned the workers.

Tight deadlines for the work to be finished before the end of the summer meant workers had to be underground before the fumes dispersed.

"This was a big lesson for us and we have added more ventilation underground to ensure the safety of our workers," Xu said.

The project company has also sent two doctors to the construction site to stand by. Any person feeling uncomfortable will get first aid.

Xu said the incident would not affect the expected completion date in October.

(China Daily August 5, 2004)