Japan has introduced revised procedures under the Chemical Substances Control Law (CSCL) aimed at streamlining the evaluation of new polymeric chemical substances.
In April, 2026, the Ministry of Health, Labour and Welfare (MHLW), Ministry of Economy, Trade and Industry (METI), and Ministry of the Environment (MOE) jointly released the results of public comments on proposed revisions to testing methods used for determining new chemical substances under the CSCL. The ministries also promulgated a revised notification, which will take effect on June 1, 2026.
In preparation for implementation, the ministries published the “Guidance for Notification of the Polymer Flow Scheme Based on the Evaluation of Chemical Structure and Properties” Version 1.0. The guidance provides the implementation framework for a more efficient approach to polymer safety assessment.
The key change under the revised notification is the introduction of a “polymer flow scheme based on chemical structure and properties.” Previously, the CSCL required polymers to satisfy criteria based primarily on testing data related to physicochemical stability and solubility. Under the revised framework, additional criteria linked to chemical structure and polymer properties have been introduced.
As a result, certain polymers may now qualify for exemptions from previously required polymer flow scheme tests if they meet specified structural or property-based conditions. These include polymers with highly stable backbone structures, polymers without concerning chemical groups in side chains or end groups, polymers that are insoluble in water or organic solvents, or polymers with an extremely large molecular size, defined as a number-average molecular weight of 100,000 or greater.
The guidance outlines three key evaluation areas:
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Main Chain Requirements
The polymer backbone must consist exclusively of highly stable bond types that are not readily degraded in the environment. Examples include carbon–carbon bonds, phenylene groups, imide bonds, amide bonds, ester bonds, urethane bonds, ether bonds (excluding acetals), and siloxane bonds.
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Side Chain and End Group Requirements
Where the backbone is sufficiently stable, additional assessment focuses on side chains and end groups. If these portions do not contain structurally concerning functional groups such as salts, alkoxysilanes, acetals, acid anhydrides, amide bonds, ester bonds, or urethane bonds, certain testing requirements may be waived, subject to specified conditions.
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Property-Based Requirements
If the polymer does not fully satisfy the structural criteria, evaluation may instead rely on specific physical properties. Polymers that are insoluble in both water and organic solvents, or that have a number-average molecular weight of at least 100,000, may also qualify for exemption from polymer flow scheme testing.
The guidance additionally introduces streamlined procedures for preparing notification materials. Companies can input polymer structural and property information into a standardized Excel template provided by METI, which automatically determines eligibility under the polymer flow scheme. The completed file is then converted into PDF format for submission.
