1.

Takeaways from the Categorization of Toxic Substance Designation and Management System

When categorizing the former toxic substances into three types of Hazardous Substances to Humans, the content standards for mixtures for each type of Hazardous Substances to Humans have also been newly established. As a result, the content standards for a significant number of substances now differ from the previous standards. Particularly for substances whose content standards for Harmful Substances to Humans are lower compared to the previous standards, mixtures containing such substances may not have been considered a toxic substance under the previous standards but may now be regulated as Hazardous Substances to Humans.
 
As one example, carbon monoxide (CAS No. 630-08-0) has a unique identification number of 2023-1-1123 as a Hazardous Substance to Humans. Under the former Notification on the Designation of Toxic Substances, carbon monoxide and mixtures containing at least 25% carbon monoxide were classified as toxic substances. However, under the amended Notification on the Designation of Substances with Acute Human Toxicity, Substances with Chronic Human Toxicity, and Substances with Ecological Toxicity (National Institute of Chemical Safety Notification No. 2025-19 or “NICS Notification”), mixtures containing at least 0.3% carbon monoxide are considered “Substances with Chronic Human Toxicity,” and mixtures containing at least 25% carbon monoxide are considered “Substances with Acute Human Toxicity.” Accordingly, a mixture containing 10% carbon monoxide would not have been considered a toxic substance under the previous standards, but such mixture would now be considered a Substance with Chronic Human Toxicity under the new standards. Accordingly, any business handling such a mixture would be subject to various obligations for handling hazardous chemical substances.
 
In light of the above, it is advisable for businesses to confirm whether the content standards applicable to the substances they handle have changed through the recent amendments. Article 1 of the Addenda to the NICS Notification stipulates that the amendments will begin to apply from January 1, 2026 for Hazardous Substances to Humans whose content standards are lower than the former toxic substance designation standards, and Article 3, Paragraph 2 of the Addenda provides separate grace periods as below for substances that were handled prior to January 1, 2026.
 

2.

Changes from the Proposed Amendment (1) – Classification Standards for Substance with Unconfirmed Hazard
 
As the amended K-REACH newly defined “Substance with Unconfirmed Hazard,” the K-REACH Enforcement Rules set forth detailed criteria for such substance. The proposed amendment to the Enforcement Rules initially categorized a substance as a Substance with Unconfirmed Hazard if any of the five hazard categories (e.g., acute oral toxicity, skin corrosion) are unconfirmed. However, Appendix 1-2 of the finalized version of the amended K-REACH Enforcement Rules removed “skin corrosion” from the hazard categories. Therefore, a substance will be categorized as a Substance with Unconfirmed Hazard if any of the following four hazard categories are unconfirmed.
 

3.

Changes from the Proposed Amendment (2) – Requirements to Amend the Reporting of New Chemical Substances

Article 11-2 of the proposed amendment to the K-REACH Enforcement Rules added a new ground for amending the reporting of a new chemical substance where the substance no longer meets the standards for Substance with Unconfirmed Hazard. However, this was removed in the finalized version of the amended K-REACH Enforcement Rules. Accordingly, there is no obligation to amend even if the substance, which was considered a Substance with Unconfirmed Hazard at the time of the initial reporting, later ceases to be considered as such.
 
However, the K-REACH Enforcement Rules still require amending the reporting of a substance if its classification and labeling change based on new information on the characteristics or hazards of the substance or based on new information on the substance’s risk affecting human health or the environment (Article 11-2, Paragraph 1, Item 3, Sub-Items a and b of the K-REACH Enforcement Rules). Accordingly, an amendment must be filed if hazard category, which was unconfirmed at the time of initial reporting, becomes available.