A court on Tuesday acquitted the former heads of SK Chemical Co. and the consumer goods company Aekyung Industrial Co. in a deadly humidifier sterilizer case.

The Seoul Central District Court found both Hong Ji-ho, the former CEO of SK Chemical, and Ahn Yong-chan, the former CEO of Aekyung Industrial, not guilty of professional negligence resulting in death.

They were accused of manufacturing and selling Humidifier Mate, a humidifier sterilizer that includes harmful chemicals, in the early 2000s.

But the court said the causal relations between lung-related illnesses such as asthma and the chemical substances used to make the product -- methylchloroisothiazolinone (CMIT) and

methylisothiazolinone (MIT) -- have not been firmly established.

The product, which was sold in the local market from Sept. 2002 to Aug. 2011, was blamed for the second-most deaths and lung-related injuries after a similar product by Oxy Reckitt Benckiser, the local unit of British hygiene product maker Reckitt Benckiser Group plc (RB).

The humidifier disinfectant scandal is one of the country's worst consumer goods disasters.

In 2011, consumers started to report deaths and illnesses allegedly tied to humidifier disinfectants, widely used in households in dry winters. A government-led investigation confirmed the link between the two in February the next year.

According to the Ministry of Environment, a total of 7,103 damage cases, including more than 1,500 deaths, has been reported as of Dec. 29. Among them, 4,114 cases have been confirmed to be related to toxic humidifier disinfectants.

In July, the Special Commission on Social Disaster Investigation called official tallies "the tip of the iceberg" and estimated the actual figures to be much higher at approximately 670,000 relevant cases and 14,000 deaths.

In January 2017, Shin Hyun-woo, the former Oxy chief from 1991 to 2005, was sentenced to seven years in prison for causing homicide through professional negligence and falsely advertising the company's disinfectant as safe. Three other employees at the company were also given prison terms on similar charges.

In May that year, the company apologized and offered to make financial reparations to the victims.

In August 2019, Ko Kwang-hyun, another former CEO of Aekyung Industrial, was sentenced to 2 1/2 in prison for covering up toxicity-related data on the company's disinfectant product. (Yonhap)