ECETOC Task Force develops weight-of-evidence framework for assessing chemical persistence

Brussels, 9 December 2021 – A Task Force from the Centre for chemical safety assessment (ECETOC) has just published a proposed a new framework for the assessment of chemical persistence (P) in the environment in the peer-reviewed journal Integrated Environmental Assessment and Management (IEAM).

Assessing the P of chemicals in the environment is a key element in existing regulatory frameworks to protect human health and ecosystems. One of the main challenges is that today’s frameworks, often developed for legacy chemicals that are no longer used, rely on simplistic and reductionist evaluation schemes that may lead today’s substances to be falsely assessed as persistent, or the other way around.

The ‘Moving Persistence Assessments Into The 21st Century’ Task Force‘s paper proposes a generalised and more flexible conceptual framework to move P assessments into the 21st Century. It explores the application of weight-of-evidence (WoE) and overall persistence to the evaluation steps. In a second ‘companion paper’ also submitted to IEAM, which will be published in early 2022, the Task Force addresses scientific opportunities to improve the accuracy and reliability of laboratory methods involved in persistence assessment.

The Task Force’s work was prompted by recent progress in scientific understanding of the underlying processes of persistence and degradation which provide an opportunity to develop an improved framework, as well as best practices for persistence and degradation assessments. The WoE approach to organise and interpret data proposed in the paper enables a more consistent, transparent and thorough assessment of persistence.

Persistence assessment – as part of chemical safety assessment – is a key element in existing regulatory frameworks to protect human health and ecosystems from harmful substances of concern. But persistence is extremely complex: it is determined by a combination of chemical specific properties and environmental factors, and it also involves multiple processes in multiple ‘compartments’ (e.g., air, water, soil, sediment and the different plant and animal life of a region). The proposed assessment framework aims to integrate transparently all the available information in an acceptable way for regulators.

Persistence in the environment is one of the most important criteria in the regulation of organic chemicals. Besides being used for prioritising hazardous chemicals, it is central to determining chemical exposure and any subsequent risk to the plant and animal life of a region.

Chemical pollution is one of nine factors identified that threaten to destabilise our Earth system processes. The effects of chemical exposure due to human activities is thus one of humanity’s greatest challenges. In this context, persistence (P) has been proposed as a central indicator to help quantify boundaries for different substances in defining a ‘safe operating space for humanity’.