This report is a synthesis of the debate with Dr. Barbara Maher in the conference series “Facing climate change”, organised by the Catalunya Europa Foundation as part of the Re-City project, in collaboration with BBVA. This session, entitled "The effects of ultrafine air pollution particles on health” consisted of a public lecture, a lunch-debate that brought together actors from the economic, social, political and business sector of Catalonia, and a meeting with academics.