Zheng has given suggestions to hundreds of workers with occupational diseases who sought help from him over the phone.

What he saw in many families made him quite sad and upset.

"I once went to a poverty-stricken county in Guizhou province where 192 workers in a factory had black lung. There is a smell of death in the atmosphere of the local villages where middle-aged men only have enough strength to breath because of the disease," he said.

"About 90 percent of the black-lung patients are hostile toward society because they were frequently turned down by their bosses, hospitals, local officials and so on."

He also accompanied some black-lung patients to help them win lawsuits against their bosses.

Zhang Shiqian, a lawyer in Hebei province who has cooperated with Zhang Haichao since 2009 providing legal aid for black-lung patients, said Zhang's participation had helped dozens of workers win lawsuits.

The lawyer recalled a case in which a worker with black lung in Sichuan province failed in a lawsuit against his boss, who refused to compensate him during the first trial in 2010.

The worker appealed for a second trial and invited Zhang Haichao to come to the hearing. Zhang, with many journalists in tow, went to the second trial and the worker received compensation of 150,000 yuan.

"I don't think Zhang Haichao's appearance in the court interfered with the judicial process," the lawyer said. "As a public figure, his appearance could bring more transparency to the lawsuit and make the final judgment more fair and reasonable."

Zhang Haichao said he had appeared in court hearings for more than 30 black-lung lawsuits, and helped about half of the workers win.

Though his appearance has helped workers gain compensation, Zhang hopes a long-term mechanism could be established to prevent occupational diseases.

"Under current laws, the most serious punishment for the managers whose companies have caused occupational illness is just a fine of 300,000 yuan, which is a piece of cake for most companies," Zhang said.

About 700,000 people were suffering from work-related diseases in 2008, according to the National People's Congress.

Most of the occupational diseases were reported in small and medium-size firms and about 80 percent of the diseases were black-lung diseases.

"The doctors told me in 2009 that I can live for another seven years at most," he said.

"What I want to do is to help as many black-lung patients as possible when I am still alive," he said. "They made contributions to the country's economy, and they should be respected rather than discarded."

Xiang Mingchao and Jiao Hongchang contributed to this story.