From the Department of Anaesthesiology of the Erasmus University Medical Centre Rotterdam, Rotterdam (WD, RJS, EMG), the Department of Industrial Ecology of the Institute of Environmental Sciences (CML), Leiden University, Leiden, The Netherlands (VG, LD, RHH, LFCMvO)

Correspondence to Wouter Droog, MD, the Department of Anaesthesiology, Erasmus University Medical Centre Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. Tel: +31 10 703 3458; e-mail: [email protected]

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