When Han Hye-kyung finished high school and got a job at Samsung, her family celebrated with a barbecue. But within two years, she stopped menstruating. And then she couldn’t walk straight. And then doctors found a brain tumor, something she and her family claim came from toxins at a factory run by the South Korean tech giant.

Han and her mother are among a small group of Koreans who say there’s a dark side to this country’s most iconic conglomerate. They say conditions at a Samsung Electronics production plant caused hundreds of rare diseases over the past two decades, some fatal, with most victims in their 20s or 30s.

The fight between Samsung and dozens of former workers persisted for years on the fringes. But the plight of those ex-employees has suddenly forced its way into the mainstream, reflecting South Korea’s growing concern about safety and corporate accountability.

Samsung and other chaebol, as the conglomerates are known, have long stood as the unassailable patriarchs of South Korea’s Third-World-to-riches rise. But in the past few months, lawmakers have demanded that Samsung provide an explanation for the spate of rare diseases. A crowd-sourced movie inspired by the issue hit theaters. And recently, Samsung apologized in a nationally televised news conference for its “lack of attention” to the pain and distress of former employees with the unusual illnesses.

There’s no clear proof linking the diseases with factory conditions. Samsung said in a statement to The Washington Post that it is “meeting or exceeding” industry health and safety standards and emphasized a series of safety innovations that it called “best-in-class.” But some politicians and activists here say the employees’ health problems highlight the faults of a company that emphasized productivity over safety and prevented the formation of workers’ unions.

For those who have pushed Samsung to acknowledge the diseases, the recent apology was a partial vindication, coming after years in which Samsung questioned their credibility. Samsung promised compensation for victims but pointedly did not claim responsibility. Han and her mother, Kim Shi-nyeo, watched the announcement on an off-brand flat-screen at their rented apartment; Kim had sold nearly every Samsung product she owned because just looking at the logo made her angry.

Han, severely disabled by the surgery to remove her brain tumor, beat her chest as she heard Samsung Electronics chief executive Kwon Oh-hyun say he was “heartbroken” by what had happened.

Kim teared up.

“I felt, to an extent, like all those years we’ve had to go through were recognized,” Kim said. “At the same time, the fact still remains that my daughter has to live the rest of her life this way.”

Complicated claims

Samsung is known globally for its televisions and smartphones, but within Korea, its influence is broader — that of a do-everything titan that sells life insurance, builds apartments and accounts for one-fifth of the nation’s gross domestic product.

Those who study Samsung say the company is increasingly sensitive to blemishes on its image as its ailing chairman, Lee Kun-hee, prepares to pass the reins to his only son.

“The social mood is changing in Korea, and I think Samsung sensed that,” said Kim Sang-jo, an economist at Hansung University who specializes in the conglomerate. “The [rare diseases] had become a symbolic problem for Samsung. It was starting to be seen as a very arrogant and stubborn company.”

Concern about Samsung’s factory conditions first surfaced seven years ago, when two former employees who had worked side by side, Hwang Yu-mi and Lee Suk-yeong, died of leukemia within months of each other. Hwang was 23, and her father, a taxi driver, felt the deaths couldn’t be a coincidence.

In the years since, about 200 other people have claimed sicknesses from Samsung production lines, mostly from the Giheung plant 20 miles south of Seoul, which manufactures semiconductors and liquid crystal displays.

But the claims are complicated. Most mainstream medical experts say that the causes of brain tumors and leukemia are essentially unknown. Still, there are some factors that can increase the risk, including exposure to radiation and benzene. The U.S. Department of Health and Human Services says “long-term exposure” to high levels of benzene can cause leukemia and some cancers.

Like other high-tech manufacturers, Samsung uses potentially harmful chemicals on its production lines, but not at levels exceeding safety standards, according to studies that the company has permitted of its workplaces. Samsung questions the results of a Seoul National University study that found benzene in samples collected at the Giheung facility, saying it does not use that substance on its production lines.

In part because of that ambiguity, South Korea’s government-run workplace compensation agency has sent conflicting signals about whether it thinks the claims are legitimate. In four cases, the agency has determined that the diseases were workplace accidents, the result of chemical exposure, according to Lee Jong-ran, a lawyer who represents many of those who have fallen ill.

But in 23 other cases, including Han’s, the agency said there was no clear correlation. Those workers have appealed to the courts, where they’ve squared off against the compensation agency and faced yet another challenge — Samsung has lent its high-profile lawyers to the government to help with its defense. (Samsung said in May that it would withdraw its lawyers from the cases.)

The diseases were reported by people employed by Samsung in the late 1990s and early 2000s, and the company has since revamped its Giheung plant. Still, several employees who worked there say Samsung for too long paid insufficient attention to worker safety. During occasional power outages, air filtration systems would shut down. Work would stop temporarily, but resume before the gases were entirely cleared, they said.

“It’s very expensive to stop a [production] line for a long time,” said Ryu Ui-seok, a former Samsung engineer who worked at Giheung from 2004 until 2006 and is in good health. “After even a brief power outage, you’d smell the chemicals very strongly” as people got back to work.

Most of the workers at Giheung were women, recent high school graduates. During the one-month orientations held for newcomers, they were told about the history of the company and the apartments they’d one day be able to afford, according to several former employees. They were given detailed instructions on how to keep the production line clean, an essential for semiconductor manufacturing. But they were told almost nothing about safety or the chemicals they’d be dealing with, they said.

“All we learned was how to be an efficient worker,” said Hong Sae-mi, who joined Samsung at 19 and has multiple sclerosis, a disease she says is workplace-related. “The emphasis was on the product, not the people.”

In a statement, Samsung said that even dating to the 1990s, 10 of 200 mandatory education hours for employees were devoted to safety. Employees were instructed on how to handle chemicals and deal with accidents. Samsung also said that in 2007, it implemented a round-the-clock chemical monitoring system, and that out of an “abundance of caution,” chemical levels were kept to one-tenth of legal limits.

Samsung declined to discuss Han’s case. A company spokeswoman said that in the West, apologizing could be seen as an admission of responsibility.

“But the employees are like our family, and the company would like to offer help when the family is in trouble,” said the spokeswoman, speaking on the condition of anonymity because of the sensitivity of the issue. “Instead of looking into whose fault it is, we try to give help first.”

Fighting a lost cause

Han, who left Samsung in 2001, developed the menstruation problems while still at the company. But her more serious health issues emerged later; her brain tumor was diagnosed in 2005. In a 2012 blog post, Samsung noted that some ex-employees’ illnesses surfaced well after they left the company, making it difficult to draw a link.

Han can’t tell her own story. She has full comprehension, but she can barely speak — only a few words now and then. After years of physiotherapy, she can dress herself, but she cannot button her shirts. She cannot write. She can talk on the phone, but only if her mother holds it to her ear.

For all the attention that the claims against Samsung have received in recent months, those dealing with diseases have suffered in private for years. In Han’s case, the best-case scenario is that she’ll “one day be able to walk to the dinner table,” Kim said.

After doctors discovered Han’s tumor, she underwent high-risk surgery. She emerged from the 12-hour operation alive, but much different. Her arms flailed uncontrollably and she couldn’t lift her head. She had quadruple vision.

It was only in 2008 that Kim heard about the other, comparable cases. Friends told her that fighting Samsung was a lost cause, given its political power and clout with the news media. But Kim joined a growing group of victims and their relatives who held memorial services and brandished banners in front of Samsung’s headquarters. Kim sold a restaurant she owned and became a full-time caretaker for her daughter. A group representing the families has paid Han’s medical bills over the past two years.

Both the government agency and a Seoul administrative court have ruled there’s no confirmable link between Han’s condition and her time at Samsung. But Kim says she’s “100 percent sure” there is. There is no family history of brain tumors or other rare diseases, and Han never showed health problems before taking her job at Samsung, her mother said.

Kim is now hoping to receive compensation from Samsung in a negotiation process. Her goals are simple. She wants to outfit her apartment with grasp bars and other devices that can help her daughter more easily live at home.

“I want Samsung to think about all the years my daughter cannot work,” Kim said. “She will need help for the rest of her life.”

Yoonjung Seo contributed to this report.

CORRECTION: An earlier version of this article incorrectly stated that Samsung uses benzene on production lines used for the manufacturing of semiconductors and liquid crystal displays. Samsung does not use benzene on its production lines, the company says. The article should have also made clear that whether Samsung used benzene in the past is a matter of ongoing debate between activists, former workers and the company. Samsung disputes the findings of a Seoul National University analysis that found benzene in samples collected at a Samsung factory. The article has been updated.