Largely unnoticed on the streets of South Korean cities and towns, more than one million foreigners labor in factories and farms at wages considerably below those of most South Koreans.

While powerful labor unions demand and often get wage increases and bonuses for native Koreans, the country’s hidden workforce, drawn from the large Korean-ancestry community in Communist China and also from Southeast Asian countries, battles discrimination — and often hazardous working conditions.

It was that way for “foreigners” — mostly Koreans with Chinese passports — with jobs in a factory producing the highly explosive lithium compound used in mobile phones. 

Twenty of them were among at least 22 reported killed in an explosion and fire that rocked the factory at the city of Haeseong about 30 miles south of Seoul. The blast killed nearly half the 48-person work force at the factory, owned by a South Korean company, Aricell. 

The fact that almost all the factory staff were foreigners doing the kind of “dirty, difficult and dangerous” work that most Koreans avoid regardless of their own problems finding jobs, immediately raised the specter of the abuses suffered by foreigners on Korean payrolls.

Migrant employees “continue to have their wages withheld and to work excessively long hours for lower wages” than than Koreans “in similar jobs,” said a report issued by Amnesty International well before the latest incident. 

Migrant employees “continue to be denied the right to organize in legal trade unions and to experience high levels of verbal and physical abuse in the workplace,” the report said. “Their work is often dangerous.”

Although no charges have yet been filed placing blame for the explosion, the employees were obviously willing to do a tough job in an industry known for dealing in dangerous materials prone to exploding. 

Probably no substance is more volatile and risky than lithium, according to a study by the German company, Dragerwerk.

So volatile is lithium that questions have been raised about whether it’s safe to transport products with lithium batteries on planes. “Lithium batteries are highly flammable and can catch fire or explode if not handled properly,” said the Drager report. 

The risk, the company adds, “is especially high during the manufacturing process, as the batteries are often exposed to high temperatures, charging variances and pressure.”

The blast was sure to trigger more investigations and commentaries on the conditions under which foreigners work in South Korea. That in turn raises the question whether the fire could prove a catalyzing event on a par with the Triangle Shirtwaist fire at New York City in 1911.

That disaster, in which more than 140 employees of a garment sweatshop died, sparked what America’s Occupational Safety and Health Administration called a “general awakening” as to the need for reform of laws relating to workplace safety.

While Korean authorities look for specific causes of the explosion, they might also consider a report on foreigners working in Korea issued by the International Journal for Equity in Health. 

“When compared to the general South Korean population,“ said the report, “the undocumented experienced the worst outcome, followed by the documented, and then the general population.”

The report added that “the undocumented migrant” employees “were more likely to smoke cigarettes than the general population.”