Carbon emissions associated with clinical trials: a scoping review

Objectives: To review and synthesize available evidence on carbon emissions associated with clinical trials to inform future research on design and delivery of greener trials. Study Design and Setting: We performed a scoping review by following the Joanna Briggs Institute guidance and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews. A systematic search was conducted on MEDLINE (Ovid) from January 1, 2007, to April 15, 2024, with no geographic and language restrictions complemented by forward and backward citation analysis (snowballing). We included all types of research literature within the context of clinical trials reporting any aspect related to trial specific carbon emissions. Results: Twenty-two articles were identified as eligible and included in the review. Most included studies (n = 17, 77%) were published between 2020 and 2024. Over half of the included studies (n = 13, 59%) were primary research articles with the majority reporting carbon audits of trials and their associated processes. The remaining literature comprised secondary studies (n = 3, 14%) and opinion pieces (n = 6, 27%). Diverse and evolving approaches to studying trial-related carbon emissions were identified alongside several carbon hotspots including those associated with trial-related travel, trial facilities, and sample lifecycle. Conclusion: The literature on carbon emissions associated with clinical trials has focused on studies reporting carbon audits of trials and their associated processes. Efforts have been made to quantify the trial carbon output with variability in methods and carbon output. Despite the development and evolution of carbon measurement tools, strategies to mitigate trial specific carbon emissions are still much in need. (c) 2025 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).