Towards a proportionality assessment of risk reduction measures aimed at restricting the use of persistent and bioaccumulative substances.

International chemicals legislation aims at adequately controlling persistent organic pollutants (POPs) and substances of very high concern (SVHCs), such as persistent, bioaccumulative, and toxic (PBT) and very persistent and very bioaccumulative (vPvB) substances, with a view to progressively substitute these substances with suitable less-hazardous alternatives. Using cost-effectiveness analysis (CEA) to assess the (dis)proportionality of measures to control such substances (collectively called "PBT" in the present paper) requires benchmarks. The present paper provides building blocks for possible benchmarks by looking at the cost-effectiveness estimates for regulatory measures that have been applied or considered for various PBT substances. These cost-effectiveness estimates vary widely, and the main factors possibly explaining this variation are discussed. The available cost estimates currently do not allow deriving a value for society's willingness to pay to reduce PBT presence, use, and emissions because decisions referring explicitly to these estimates are scarce. Roughly speaking, the available evidence suggests that measures costing less than €1000 per kilogram PBT use or emission reduction will usually not be rejected for reasons of disproportionate costs, whereas for measures with costs above €50 000 per kilogram PBT such a rejection is likely. More research is needed to strengthen the evidence base and further elaborate a systematic approach toward proportionality benchmarking. Integr Environ Assess Manag 2017;13:1100-1112. © 2017 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).