What’s the concern about persistent chemicals? Insights from a Delphi study

Persistent chemicals are in the focus of regulators owing to their potential for long-term impacts on the environment and on human health. Since these impacts are difficult to predict and empirical data on their risks and effects is scarce, expert knowledge is a source of information that can facilitate a prioritisation of persistent chemicals for regulatory action. This Delphi study explored experts’ opinions on what kind of information is considered to be relevant to specify the concern associated with persistent chemicals. In addition, we asked experts to rate the importance of different factors of persistent chemicals to characterise the concern. Results show that experts considered a wide range of factors important, with factors related to the temporal and spatial scale of pollution as well as related to the severity of potential impacts receiving the highest ratings. The agreement among experts was relatively low, which may partly result from their different professional backgrounds, including different affiliations and geographic regions. When asked about recently emerging topics in the risk management of persistent chemicals, the majority of participants considered PMT chemicals to be of equal concern as PBT/vPvB chemicals. Also, they supported that ‘extreme persistence’ needs to be distinguished from the current regulatory definitions of ‘persistent’ and ‘very persistent’. Overall, the results of this Delphi study imply that for the effective risk management of persistent chemicals regulators should base their decisions on a broader range of information than exclusively focussing on a limited set of hazard criteria. • This Delphi study explores experts’ views on the concern about persistent chemicals. • Participants consider a large variety of factors relevant to specify the concern. • Factors ranked highest are related to the scale and the severity of impacts. • Most experts are equally concerned about PMT as about PBT chemicals. • A majority of experts sees a need to distinguish ‘extremely’ persistent from persistent chemicals.