IVL Swedish Environmental Research Institute

Urban greenery has been identified as a potential strategy for air pollution mitigation. Greenery provides surfaces for pollutant deposition and can effectively reduce PM10 concentrations in urban environments. This report aims to provide an understanding of how to incorporate urban greenery as a measure for air pollution mitigation in air quality management. We have specifically focused on how urban greenery can be used as a measure in air quality plans.  An air quality plan is a regulatory strategy aimed at improving air quality in regions that do not meet the standards set by the European Union's air quality directives.

This work includes a review of the use of urban greenery as a strategy for air pollution mitigation in Swedish air quality plans.Five of the total twelve cities that has developed air quality plans have incorporated measures on urban greenery in their plans. The Swedish air quality plans describe urban greenery as a “long-term, strategic and knowledge intensive” measure. The main justification for including urban greenery is not its direct effect of reducing air pollutant concentrations through deposition, but rather its indirect effect of reducing emissions attributed to decreased traffic. Based on available information, it remains unclear if urban greenery has been implemented as a PM10 mitigation measure in Swedish municipalities.

Additionally, we found no evidence of municipalities having evaluated the impact of urban greenery on PM10 levels. This lack of data makes it challenging to assess the effectiveness of greenery in mitigating particulate pollution across urban areas. The air quality directive states that air quality plans should primarily include powerful measures that reduce pollutant levels as quickly as possible. Therefore, the main effort in an air quality plan needs to be on emissions reductions. While urban greenery can be used as a measure for air pollution mitigation it is best used as a long-term strategical measure. Therefore, urban greenery as a measure to reduce air pollution is better to include in the development of preventive air quality strategies, for example in air quality roadmaps. However, urban greenery barriers can be used to prevent transport of traffic pollutants to sensitive locations e.g. between a major road and a school, when a relatively quick measure to reduce school yard exposure is needed.