An Associated Press investigation has found South Korean authorities have repeatedly withheld from workers and their bereaved families crucial information about chemicals they were exposed to at Samsung’s computer chip and liquid crystal display factories. Sick workers need access to such data through the government or the courts to apply for workers’ compensation from the state. Without it, government officials commonly reject their cases.

In at least six cases involving 10 workers, the justification for withholding the information was trade secrets.

South Korean law bars government agencies from withholding public health and safety-related information because of trade secrets concerns, but there are no penalties for violations.

Samsung no longer omits lists of chemicals used on production lines from reports on workplace safety, as it did in Hwang Yu-mi’s case. But officials have withheld details about exposure levels and how the company’s chemicals are managed.

“Our fight is often against trade secrets. Any contents that may not work in Samsung’s favour were deleted as trade secrets,” said Lim Ja-woon, a lawyer who has represented 15 sick Samsung workers.

Lim’s clients have been unable to see full, third-party reports on inspections of the factories and have accessed only excerpts of some independent inspections in some court rulings, he said.

Samsung says it has never “intentionally” blocked workers from accessing information and that it is transparent about all chemicals it is required to disclose to the government. It said in a statement that there was no case where information disclosure was “illegally prevented”.

“We have a right to protect our information from going to a third party,” Baik Soo-ha, a Samsung Electronics vice-president, said.

Government policies have generally favoured Samsung and other “chaebols”, or corporate conglomerates, that powered South Korea’s rapid industrialisation after the 1950-53 Korean war.

Officials say corporate interests take priority, evaluating trade secrets claims is difficult, and they fear being sued for sharing data against a company’s will.

“We have to keep secrets that belong to our clients,” said Yang Won-baek, of the Korea Occupational Safety and Health Agency, or KOSHA.

Samsung is by far South Korea’s biggest company, with about 100,000 workers. It has dominated memory-chip makers since the early 1990s, but that success involves use of toxic and often carcinogenic chemicals such as arsenic, acetone, methane, sulfuric acid and heavy metals such as lead, well-known risks in the production of semiconductors, mobile phones and LCDs.

The worker safety group Banolim, or SHARPS in English, has documented more than 200 cases of serious illnesses including leukaemia, lupus, lymphoma and multiple sclerosis, among former Samsung semiconductor and LCD workers. Seventy-six have died, most in their 20s and 30s.

Worker safety advocates want South Korea’s courts and government to more flexibly interpret links between workplace conditions and diseases, since the exact causes of many of the factory workers’ ailments are unknown even to the medical community. They also want thorough disclosure of workplace hazards.

Since 2008, 56 workers have sought occupational safety compensation from the government. Only 10 won compensation, most after years of court battles. Half of the other 46 claims were rejected and half remain under review.

Families of the victims, mostly working-class youths from the countryside, often deplete their savings and sell their homes to pay hospital bills, ending up in subsidised housing. Some of the workers ended up incapacitated and unable to work.

Left with few options, more than 100 families accepted a compensation plan Samsung proposed last year, but many rejected it.

Hwang Sang-gi said Samsung offered him one billion won (US$864,000) in 2007 to not pursue a case over his daughter’s death. He said no, founded Banolim and joined four former Samsung semiconductor workers suffering from various blood cancers in filing for workers’ compensation.

In 2014, seven years after Yu-mi’s death, an appeals court affirmed a lower court’s finding of “a significant causal relationship” between Yu-mi’s leukaemia and her likely exposure to benzene, other chemicals and ionized radiation at work. Hwang Sang-gi received nearly US$175,000 from the government.

Samsung’s CEO issued a formal apology to ailing workers in 2014, though some of them consider it inadequate. The company promised to give workers documents they need to seek compensation, and this year it launched an ombudsman committee to oversee independent inspections of some factories.

Workers and their bereaved families want more a complete apology and changes in how compensation is awarded. Hwang and other campaigners regularly camp outside Samsung’s complex in Gangnam to protest. They view suing Samsung as a poor option; the standard of proof would be higher than in workers’ compensation cases, and under South Korean law they could not seek punitive damages.

They also say it remains difficult to get details about working conditions.

Labor ministry official Goo Ja-hwan said the government usually accepts companies’ requests to keep details secret. “We cannot evaluate whether things that companies have hidden as secrets are real trade secrets or not,” he said.

Baskut Tuncak, the UN special rapporteur on hazardous substances and waste, said in a phone interview that no government should say it’s unable to determine whether certain information is a trade secret.

“That simply allows their abuse of the system where information about hazardous substances is hidden from the public from victims under claims of confidentiality,” he said.