Supplementary Material: Festivals following the easing of COVID-19 restrictions: Prevalence of new psychoactive substances and illicit drugs

The authors sincerely thank the wastewater treatment plant operators for their help in collecting samples. The authors also thank SCIEX for the use of their instruments. Nikolaos Rousis: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie Grant Agreement No. 896141. Richard Bade: The Queensland Alliance for Environmental Health Sciences, The University of Queensland, gratefully acknowledges the financial support of the Queensland Department of Health. R. B. is the recipient of an Australian Research Council Discovery Early Career Award (project number DE220100381), and J. M. is the recipient of an Australian Research Council Australian Laureate Fellowship (project number FL200100028) funded by the Australian Government. Emma Gracia-Lor: This work was supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Complutense University in the line Program to Stimulate Research for Young Doctors in the context of the V PRICIT (Regional Programme of Research and Technological Innovation, project number PR65/19-22432). Iván Romero-Sánchez acknowledges the Complutense University of Madrid for his predoctoral grant [CT63/19-CT64/19]. The views expressed in this article are those of the author(s) and not necessarily those of the funding agencies.