The Fair Trade Commission said on Monday that it has brought the heads of four companies including two U.S.-based firms to prosecutors on charges of concealing that their humidifier sterilizers contain dangerous materials.

FTC officials said the four companies labeled their humidifier disinfectants either as “safe for the body” or “safe for the body and harm-free when inhaled.”

The legal action was taken as the nation’s health authorities came to a conclusion that sterilizers for humidifiers are related to lung disease.

The four firms are Oxy Reckitt Benckiser Ltd., Home Plus Co. Ltd., domestic sterilizer firm Butterfly Effect and a self-employed manufacturer Atorganic.

If the company heads are indicted, they could face up to two years in jail. The nation’s antitrust watchdog also imposed a total of 52 million won ($45,000) in fines.

The humidifier sterilizers produced in these firms include either Pohyhexamethylene guanidine or Oligo (2-ethoxy) ethoxyethyl guanidinium chloride, which could cause serious scarring or thickening of the lung tissues.

At least 10 people so far have died from inhaling the harmful substances contained in humidifier sterilizers, according to health officials.

Through close examination and animal testing, the Korea Centers for Disease Control and Prevention verified that the products in question have contributed to, if not directly caused, damage to the lung.

Lotte Mart and GLONM Co., which have also sold humidifier disinfectants, avoided legal punishment as they did not label these products as “safe for the body.”

By Chung Joo-won (joowonc@heraldcorp.com)