Breathe: Implementation of green barriers to mitigate air pollution in school playgrounds – case studies from UK and Argentina

Globally, more than 90% of children live in areas that exceed the World Health
Organization air pollution limits. Simultaneously, evidence has shown that children are
especially susceptible to suffer detrimental health effects caused by air pollution. Some
of these health conditions include asthma exacerbation, bronchitis, or cognitive
impairment. Innovative solutions that mitigate the risks to children’s health from air
pollution are urgently needed.

This thesis examined green (vegetated) barriers as a nature-based solution to air
pollution in school playgrounds, where children spend a large part of their day. It intends
to close the technical and application gaps for green barrier implementation. For this
purpose, real-life green barriers were installed in two school playgrounds, in Sheffield,
UK and in Buenos Aires, Argentina, and are the focus (case studies) of this research.
Through the UK case study, the research aimed to 1) assess the air pollution mitigation
potential of green barriers in school playgrounds considering the air pollution-vegetation
interaction, 2) identify the co-benefits, trade-offs and disbenefits of green barrier
implementation for school communities, and 3) understand the implementation process
and practicalities of green barriers in school playgrounds. Additionally, through the
Argentine case study, this research aimed to 4) identify barriers and solutions to green
barrier implementation in school playgrounds in a Latin American context. Action
research was carried out throughout the implementation process at both schools, and
was complemented by quantitative (air pollution monitoring and leaf microscopy) and
qualitative (interviews, surveys, and narratives) methods to achieve the various research
aims.

Air quality was only monitored at the Sheffield school, which showed that ‘thin’ green
barriers (1.00-2.20 m) have the potential to reduce air pollution when properly designed
and implemented. Air quality improvements were significant for the pollutant nitrogen
dioxide (13%), but rather low for particulate matter (2%). Despite such small reductions,
this research found that particulate matter is captured by the green barrier plants, and
that this pollution reduction mechanism is maximised by plant biodiversity. Additionally,
the Sheffield case study showed that a diligent green barrier design can provide other
social (e.g., safety, wellbeing, and increased place quality), environmental (e.g., habitat
provisioning for wildlife), and economic (increased subscription/interest in the school)
benefits, which are highly valued by the school community. Finally, this research showed
that the implementation of green barriers is largely influenced by its global context.
Specifically, the Buenos Aires case study showed that green barrier implementation in a
country without robust green intervention frameworks faces multiple obstacles, more
than previously reported in the predominantly Euro-American literature. However,
commitment, collaboration, and experimentation (as an urban living lab) can help
overcome those hurdles.

Overall, green barriers showed to be a valid complementary tool to the efforts of
reducing and mitigating air pollution, with the relevant addition of creating safe and
healthy environments for children and the broader school community.