Building evidence regarding nature-based solutions indicators and their implications for policy – the case of air quality

Air pollution is one of world's largest planetary health risk factors. Nature-based solutions (NBS) have been key in integrating air quality indicators into the urban green planning and public health discourse. Despite important contributions, approaches that include multidimensional indicators into research, planning and policies are still limited. National standards for some types of air pollutants are missing, with little evidence for a threshold for health effects. To respond to these gaps, we provide an overview and guidance for air pollution indicators, using three case studies in Europe and Latin America. We discuss the importance of context, specific pollutants and vulnerable groups and suggest new approaches at finer scales. Our findings also point out that knowledge of pollutants uptake in edible plants can give a hint to potential exposure risks for humans. Our lessons learned target specific policies and are organized into three main ideas: (a) multidimensional indicators and their implications for NBS and policy; (b) plants as biological indicators and as schools’ subjects and (c) the integration of the co-benefits to manage air quality.