Moving persistence assessments into the 21st Century: A role for weight-of-evidence (WoE) and overall persistence (Pov)

Assessing the persistence of chemicals in the environment is a key element in existing regulatory frameworks to protect human health and ecosystems. Persistence in the environment depends on many fate processes, including abiotic/ biotic transformations and physical partitioning, which depend on substances' physico-chemical properties and environmental conditions. One of the main challenges in persistence assessment is that existing frameworks rely on simplistic and reductionist evaluation schemes that may lead substances to be falsely assessed as persistent or the other way around, to be falsely assessed as non-persistent. Those evaluation schemes typically assess persistence against degradation half-lives determined in single-compartment simulation tests or against degradation levels measured in stringent screening tests. Most of the available test methods are however not applicable to all types of substances, especially substances that are poorly soluble, complex in composition, highly sorptive or volatile. Besides, the currently applied half-life criteria are mainly derived from a few legacy Persistent Organic Pollutants which are not representative of the large diversity of substances entering the environment. Persistence assessment would undoubtedly benefit from the development of more flexible and holistic evaluation schemes including new concepts and methods. A weight-of-evidence (WoE) approach incorporating multiple influencing factors is needed to account for chemical fate and transformation in the whole environment so as to assess overall persistence. The aim of the present paper is to begin to develop an integrated assessment framework that combines multimedia approaches to organize and interpret data using a clear WoE approach to allow for a more consistent, transparent and thorough assessment of persistence. This article is protected by copyright. All rights reserved.