In a scientific opinion article published on October 20, 2021, in the journal Environmental Science and Technology, researchers Zhanyun Wang, Helene Wiesinger, and Ksenia Groh from ETH Zürich and Eawag in Switzerland identify and analyze what they see as major gaps in the identification and communication of chemicals used within polymers and in substances with an unknown or variable composition. The authors argue that the “high prevalence” of these chemicals and the lack of communication about their identities “significantly hampers public oversight on chemical safety,” and they outline a set of recommendations to address this.

Based on a recent analysis of global chemical inventories (FPF reported), more than 70,000 chemical substances are registered on the global market as either polymers or as substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs). Within the EU’s REACH regulation, 15% of all substances are UVCBs, and approximately 45% of those are listed as being manufactured or imported at volumes greater than 100 metric tons annually. The article explains that up to 200,000 different substances are estimated to be present in these polymers, which have annual global production volumes on the scale of metric megatons.

The authors primarily blame the limitations and built-in ambiguities on the Chemical Abstracts Service (CAS) Registry Numbers used to identify chemicals globally. For polymers, these CAS numbers omit “important characteristics such as molecular-weight ranges and molecule parts other than monomers or single repeating units.” They further do not describe the presence of impurities such as from production processes or starting materials, and CAS fail to show percentage compositions of individual monomers. For UVCBs, insufficiently defined mixtures of chemicals are labeled under general name headings or labeled based on just one of the significant components it contains. This practice excludes information about the true composition and allows for significant ambiguity.

Largely developed in the 1970s, a core problem of the CAS system in this context is that “CAS names often cover a wide range of substances with different compositions that may have distinct hazardous properties, environmental fates, bioaccessibility, degradation potential, and implications for risk management.” Looking ahead, the authors argue that reducing the variability of chemicals used may be challenging and current ambiguities are rather caused by the habitual, systematic omission of key information within the current labelling framework. They suggest three actions to help address this:

  • Regulators and producers should close these knowledge gaps by “providing an accurate, publicly accessible overview of all commercial polymers and UVCBs, including typical impurities therein.” This includes systemic investigation into substances lacking complete information and incorporating this principle into regulatory changes, such as the ongoing REACH revision.
  • Create a central information hub to host information currently spread across different governmental institutions and manufacturers.
  • Further develop and integrate novel chemical structure-based machine-processable identifiers into existing systems registration and identification systems

Polymers are not yet registered under REACH, but the EU Competent Authorities for REACH and CLP (CARACAL) subgroup on polymers is currently working on developing a proposal for polymer registration under REACH (FPF reported and here). The subgroup on polymers, composed of EU member states, industry representatives, and NGOs, gathers regularly to discuss the topic and held its fifth meeting on October 20, 2021. The next meeting is scheduled for mid December 2021.



Wang, Z., Wiesinger, H., and Groh, K. (October 19, 2021). “Time to Reveal Chemical Identities of Polymers and UVCBs.” Environmental Science and Technology