AP Photo/Ahn Young-joon

In this April 22, photo, Hwang Sang-gi, father of Hwang Yu-mi, a former Samsung factory worker who died of leukemia at the age of 22, wears shoes in order to an interview outside Samsung buildings in Seoul, South Korea. Sang-gi launched a movement demanding the government investigate health risks at Samsung Electronics Co. factories after learning another worker at the same semiconductor line of Yu-mi also had died of leukemia.

SEOUL, South Korea (AP) — As a high school senior, Hwang Yu-mi went to work bathing silicon wafers in chemicals at a Samsung factory that makes computer chips for laptops and other devices. Four years later, she died of leukemia. She was 22.

After Yu-mi’s death in 2007, her father, Hwang Sang-gi, learned a 30-year-old worker at the same semiconductor line also had died of leukemia. Convinced they died because of their work, the taxi driver launched a movement demanding the government investigate health risks at Samsung Electronics Co. factories.

When Hwang sued after his first claim for government compensation was denied, he struggled to get details about the factory environment. A government document he received about his daughter’s workplace had a section for listing the chemicals used there, but that space was left blank because Samsung did not release that information to worker-safety officials.

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

The justification for withholding the information? In at least six cases involving 10 workers, it was trade secrets. Court documents and interviews with government officials, workers’ lawyers and their families show Samsung often cites the need to protect trade secrets when it asks government officials not to release such data.

“Our fight is often against trade secrets. Any contents that may not work in Samsung’s favor 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 get access to full reports on facility inspections, which are produced by third parties to comply with South Korean law, but remain the property of Samsung. Only excerpts of some independent inspections can be found in some court rulings, he said.

South Korea law bars governments and public agencies from withholding corporate information needed “to protect the lives, physical safety, and health” of individuals on trade-secrets grounds, but there are no penalties for violations. Lim said the law on occupational disease compensation also obligates Samsung to give workers the data they need to make claims.

Government officials openly say corporate interests take priority, that evaluating trade-secrets claims is difficult, and that 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. “It’s about trust.”

Asked why he used the word “clients” to describe companies his government agency helps regulate, Yang said it’s probably because he treats those companies “as I treat clients.” He said the companies KOSHA evaluates also review the agency, and the finance ministry considers those reviews when it sets agency budgets.

When asked for comment, Samsung emailed a statement saying it never “intentionally” blocked workers from accessing information and that it is transparent about all chemicals it is required to disclose. It also said there was no case where information disclosure was “illegally prevented.”

However, documents from courts and the labor ministry show that as recently as last year, Samsung asked the government not to disclose details of chemical exposure levels and other inspections — even at judges’ request for use in workers’ compensation lawsuits.

In a letter to regulators signed by the company’s CEO, Samsung said that if factory details including “types and volumes of substances” were released for a workers’ compensation case, “it is feared that the technology gap with rivals at home and overseas would be reduced and our company’s competitiveness would be lowered. For that reason they are trade secrets that we treat strictly as secrets, we request not to disclose.”

Although the company no longer omits lists of chemicals as it did in Hwang Yu-mi’s case, it has recently withheld details about exposure levels and how its chemicals are managed.

Samsung is South Korea’s biggest company by far, with about 100,000 workers. Its market capitalization is more than five times greater than the No. 2 company in this country of 50 million. It employs about 45,000 people in its South Korean semiconductor and LCD departments, though not all of them are factory workers.

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

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

People who have claimed they got sick because of work they did for other major South Korean manufacturers, including Hyundai Motor, have received help from their unions in advancing their claims. Hyundai Motor now must get union approval before introducing new chemicals into its manufacturing processes. Samsung’s workforce is not unionized.

Families of the victims, mostly working-class youths from the countryside, often use up their life savings and sell their homes to pay hospital bills, ending up in subsidized 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, which covered some medical fees and some income for workers with any of 26 diseases. Some families rejected the deal.

Government policies have generally been friendly toward Samsung and other “chaebols,” corporate conglomerates that helped drive South Korea’s rapid industrialization under dictatorships after the 1950-53 Korean War.

Samsung overtook Japanese memory-chip makers in the early 1990s and through aggressive cost-cutting, bold investment and rapid construction of new factories has dominated the market for two decades.

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.

Kong Jeong-ok, an occupational health physician who works with Banolim, said new chemicals often are used before the risks from them, and from the toxic byproducts created by mixing them, are fully investigated.

Korean companies using such chemicals are required to strictly manage them, submit biannual reports showing exposure levels and give employees that information.

Samsung states on its website that its chemical management system is “rigorous” and “state-of-the art.” It has had “real-time 24/7 chemical monitoring” in all facilities since 2007, the year the government began inquiries into Yu-mi’s death.

Yet Samsung began monitoring some toxic byproducts in the air only after a 2012 inspection detected benzene and formaldehyde — both known carcinogens — at its chip factories.

Baik Soo-ha, a Samsung Electronics vice president, told the AP that Samsung has redacted trade secrets in documents given to individuals only when their requests appeared not “purely” meant to determine occupational diseases.

“We have a right to protect our information from going to a third party,” he said. Baik did not elaborate on what sort of ulterior motives Samsung believes might be behind some requests.

Samsung said it sometimes lacks information about chemicals because its own suppliers, also citing trade secrets, refuse to disclose details. It said suppliers must certify any such materials are non-toxic.

In June, for the first time, the government’s worker safety agency formally designated a case of malignant lymphoma as an occupational disease at a Samsung semiconductor factory, despite Samsung’s refusal to hand over exposure data and other information. Samsung cited trade secrets, but also said it lacked some data.