"Most of the exposed workers have already left and only a small number remain," Guo said. "We are worried that if we leave the company, our condition will get worse... we don't dare sign the agreement."

Wintek said that the company is following proper procedures for treating workers for industry-related injuries. According to Chinese laws, the workers must complete their contract or leave the job in order to receive certain levels of compensation, said company spokesman Jay Huang.

The company has handled workers exposed to n-hexane on a case-by-case basis, Huang added. Workers exposed to the chemical, but later diagnosed to be fully recovered, signed an agreement indicating this. The company used "objective measurements" in its examinations. Workers who had fully recovered would not have reoccuring symptoms.

Apple did not respond to a request for comment.

Chinese environmentalist Ma Jun, the head of the Beijing-based Institute of Public and Environmental Affairs (IPE), has been following the situation. He said the amount of compensation depends on the worker, but could vary between US$10,000 to $13,000.