ECETOC task force proposes three-tiered approach to targeted information requirements for polymers

Brussels, November 2023 – Scientists from the Centre for chemical safety assessment (ECETOC) have proposed a three-tier approach to standard information requirements for polymers where conventional risk assessment approaches (for example as under existing REACH Regulation) may not be suitable. The proposal was recently published in the October issue of Regulatory Toxicology and Pharmacology. 

Polymers cover a broad spectrum of generally very large molecules, including e.g. cellulose, waxes, and resins. They are also constituents of plastics and play essential and ubiquitous roles in everyday life.   

Polymers pose both technical and scientific challenges for safety testing and assessment due to their size, properties and/or form. Conventional risk assessment approaches currently used for small molecules may not apply to most polymers. The limited bioavailability of many polymers is a prominent difference to many small molecules and is a key consideration of the proposed approach. 

To start to address this, the ECETOC Task Force previously published a series of three technical reports (in 2019 (TR No. 133-1), 2020 (TR No. 133-2) and 2021 (TR No. 133-3)) on polymer risk assessment. Building on these reports, the Task Force has now proposed a conceptual three-tiered approach for data generation to assess both individual as well as groups of polymers.  

In short, the framework identifies tiered information requirements that can reduce animal testing whilst maintaining adequacy. Polymer grouping, and assessment of systemic bioavailability, are key aspects of the tiered approach. The Use of New approach methodologies (NAMs) can be applied as part of the tiered testing. And Tier 1 information, which excludes vertebrate testing, may be sufficient for many polymers. 

Fundamental to the Task Force’s proposal is that animal testing only be used as ‘a last resort’, while still ensuring the quality of information for the regulatory decision making. A key element is the grouping of polymers according to their chemistry, physico-chemical properties and hazard similarity, allowing tests on a particular polymer to be used across a group of polymers. The limited bioavailability of many polymers is a prominent difference to many small molecules and is a key consideration in assessing the need for higher tier testing, which typically involves experimental animals. Lastly, the proposed approach does not use manufactured tonnage volume as a trigger for higher tier testing for human health, as manufactured volume does not necessarily correlate with high exposure whilst low manufactured volume could potentially cause high exposure. 

The proposed data generation at Tier 1 is designed without the use of vertebrate animal tests. It uses in silico (computer) and in vitro (test tube) methods for toxicology and ecotoxicology data, except for short-term toxicity testing on algae or water-based crustaceans. And for many polymers requiring registration, Tier 1 data will likely be sufficient for achieving regulatory protection goals.  

Decisions on whether to generate Tier 2 data consider information on the use of the polymer and its bioavailability to humans and environmental species (including the potential to cause systemic toxicity in humans, i.e. effects on the whole body rather than a specific (local) area, such as an area of the skin surface). Needs for Tier 3 data will be based on the information from Tiers 1 and 2.  

The proposed approach for data generation will now be presented and discussed with regulators and stakeholders, and then tested in case studies. Based on the outcomes and experiences, the Task Force will refine the approach further. 

The Task Force believes its three-tiered approach minimising animal testing can provide a basis for modern and considerate data generation for the next decade, until a transition to risk assessments fully based on New Approach Methodologies is achievable in chemical regulation. One potential application of the framework could be potential future assessment of polymers under the umbrella of the REACH Regulation.