Green infrastructure (GI) includes trees, hedges,
individual shrubs, green walls, and green roofs.
GI offers many different benefits or services,
including flood risk mitigation, microclimate regulation, carbon sequestration, improved health
and wellbeing and ? the focus of this document
? air pollution abatement. Air pollution comprises variable quantities of many different types of
pollutants, including gaseous pollutants, such as nitrous oxides (NOx) and particulate matter (PM),
which is composed of particles such as black
carbon (BC). Road traffic is a dominant source of
air pollution in urban areas globally. In near-road
environments, vegetation can act as a barrier
between traffic emissions and pedestrians
(figure below), by collecting pollutants and/or
redirecting the flow of polluted air.
This document summarises best practice regarding GI implementation for improved urban
air quality and reduced pedestrian exposure
to air pollution. Generic (i.e. not site-specific)
recommendations are offered for typical urban
environments. These recommendations are
based upon contemporary scientific evidence
and knowledge, and may therefore be subject
to modification as the evidence base develops.
This guidance document consolidates major
findings from relevant publications, including a
detailed report on the relationship between vegetation and urban air quality, review articles
and other guidance documents.