Expert elicitation on the relative importance of possible SARS-CoV-2 transmission routes and the effectiveness of mitigations.

OBJECTIVES: To help people make decisions about the most effective mitigation measures against SARS-CoV-2 transmission in different scenarios, the likelihoods of transmission by different routes need to be quantified to some degree (however uncertain). These likelihoods need to be communicated in an appropriate way to illustrate the relative importance of different routes in different scenarios, the likely effectiveness of different mitigation measures along those routes, and the level of uncertainty in those estimates. In this study, a pragmatic expert elicitation was undertaken to supply the underlying quantitative values to produce such a communication tool. PARTICIPANTS: Twenty-seven individual experts from five countries and many scientific disciplines provided estimates. OUTCOME MEASURES: Estimates of transmission parameters, assessments of the quality of the evidence, references to relevant literature, rationales for their estimates and sources of uncertainty. RESULTS AND CONCLUSION: The participants' responses showed that there is still considerable disagreement among experts about the relative importance of different transmission pathways and the effectiveness of different mitigation measures due to a lack of empirical evidence. Despite these disagreements, when pooled, the majority views on each parameter formed an internally consistent set of estimates (for example, that transmission was more likely indoors than outdoors, and at closer range), which formed the basis of a visualisation to help individuals and organisations understand the factors that influence transmission and the potential benefits of different mitigation measures.

Substance prioritisation for the development of EU Acute Exposure Toxicity Thresholds (AETLs).

The aim of the EU Acute Exposure project, ACUTEX, is to develop a methodology for establishing European Acute Exposure Threshold Levels, EU AETLs, for toxic substances in relation to harm to people by inhalation. The development of AETLs is initially in the context of the risks of major accidents from chemical sites and in particular their regulation through the EU 'Seveso II' Directive. It is intended that AETLs can be used within Member States, where appropriate, to inform decisions on land-use planning and emergency planning. AETLs will not have a regulatory status. This paper describes: the selection of 21 preliminary substances to use as case studies in the development and testing of the AETL's methodology; and the development of a prioritisation methodology to inform initial substance selection for a possible further AETLs program. The work was based on consultation with experts drawn from EU major stakeholder groups. It included a Validation Exercise working with three Member States, which account for between approximately 40% and 50% of all EU Seveso II sites. From this Validation Exercise we infer that, if these three Member States are representative in terms of numbers of priority substances, then the number of EU higher priority substances for further AETLs development is unlikely to be much in excess of 50.