"Most workers whose injuries are not that serious will go back to work after recuperating for some days, and they do not ask for compensation because they are more worried about losing a job," she said.

Workers who are badly injured at work have to go through time-consuming and complicated procedures if they want to sue the employer and get treatment fees and compensation, according to Zhao.

Workers should provide documentation, including proof of employment, before they can apply for work-related injury diagnosis.

A regulation released by the Ministry of Human Resources and Social Security in 2011 requires its nationwide grassroots bureaus to use the work-injury insurance fund to pay workers' medical expenses if their employers did not provide workers' insurance coverage and refused to take responsibility for treatment fees.

Then bureaus can order employers to pay those fees, according to the regulation.

But the regulation has been poorly implemented, according to Zhao.

Huang Leping, head of the non-governmental organization Beijing Yilian Legal Aid and Study Center of Labor, said a majority of miners in State-owned enterprises are covered by work-injury insurance, but in small and medium-sized privately run mines, the rate of coverage is low.

"Miners are vulnerable to occupational diseases such as black lung, and it always takes a long time before they can receive compensation if they did not have work injury insurance," he said.