Health authorities said Wednesday that disinfectants used to clean humidifiers might have caused a fatal lung disease which killed four people, including two pregnant women.

The Korea Centers for Disease Control and Prevention advised people to refrain from using humidifier disinfectants in a bid to protect them from the deadly pneumonic diseases.

Humidifiers are widely used during the dry seasons of winter and spring, and disinfectants are mixed with water replenished to the water tank of the device.

Center official Kwon Jun-Wook told the news briefing that a group of medical experts have reached a provisional conclusion that a substance in humidifier disinfectants is likely to have caused the lung disease when inhaled.

However, the authorities refused to identify the substance, saying a thorough investigation is still underway.

Eight cases of acute pulmonary disease of unknown origin were reported so far this year, of which seven of them were women. Four of them, including two pregnant women, died while three survived through lung transplant operations. Only one recovered naturally.

Humidifier disinfectants are used in other parts of the world but no fatalities due to them had yet been reported.

Analysis of Seoul patients found that users of humidifier disinfectants are about 47.3 times higher at risk of catching the illness than non-users. The study was conducted by questioning and observing the lifestyle of 18 patients out of 28 since 2004 and all of them were said to have used humidifiers.

“The substance is used in several other products such as wet tissues, cosmetic goods, shampoo and others. But we can assure you that the risk factor is valid only when the substance is inhaled since the disease involved multiple disorders in the lungs,” Kwon said.

He said pregnant women to were more susceptible to the disease is because they tend to stay indoors and use humidifiers.

“Also when pregnant, women tend to breathe in 30 percent more air than normal. Therefore, the amount of substance they are exposed to would be larger than others,” Kwon said, adding that the conclusion results from a three-month investigation.

The authorities said they will designate humidifier disinfectants as quasi-drugs whose safety will be closely monitored by the Korea Food and Drug Administration.

The KCDC advised people to refrain from cleaning humidifiers with disinfectants. “We think precaution principle is extremely important,” Kwon said.

The center advised people to change water in the water tank of the humidifiers every day and cleanse them with neutral detergent then rinse with water more than three times.

By Bae Ji-sook (baejisook@heraldcorp.com)