By the middle of the 21st century, ambient air pollution will be responsible for premature death
every five seconds, mainly in urban areas (OCDE, 2016a). According to the WHO, air pollution attributable
to particulate matter is responsible for nearly 7 million premature deaths a year, of which
4.2 million for outdoor pollution and 2.6 million for indoor pollution. Air pollution has been identified
as a priority in the Sustainable Development Goals (SDGs) because of the burden that it poses
on human health. In a context marked by the explosion of world demography and the acceleration of
rural-urban migration, especially in emerging and developing countries, urban populations are subject
to economic, environmental and health tensions, especially among the most vulnerable populations
(the youngest and the oldest) and low-income socioeconomic status.
Our initial assumption emphasizes the role of urban morphology in urban air quality, influencing
the ’chain of transmission’ of air pollution from emission sources, to environmental concentrations,
up to the exposure of urban populations. Thus, our work takes place in a specific context of relative
inefficiency of air pollution control policies, despite a tightening of environmental regulations which
has allowed pollutant concentrations to be lowered without reducing the exposure of air pollutants
for people (HEI, 2018).
Through this study, we sought to better understand the impacts of urban form on air pollution and
on human health, of which particulate matters (PM2.5) are the main culprits, with economic, environmental
and health consequences particularly heavy for the populations of the metropolises. For this,
we first presented the main stylized facts of air pollution, urban form and health impacts. We focused
on two-way interactions between air pollution and greenhouse gases responsible for climate change.
We also discussed issues of equity and social and environmental justice regarding the spatial distribution
of air pollution, with low-income populations overexposed to air pollution, facing cumulative
risk factors and to an environmental poverty trap risk. Then, we highlight joint strategies for multipollutant
management of air and climate change, at the level of the urban area. Finally, we carried
out an assessment of the burden of air pollution and the economic cost involved for a set of cities
belonging to OECD member countries.
In order to study the effects of urban morphology, socio-economic inequalities or the economic
performance of cities on the exposure of urban populations, we carried out an empirical study of 26
cities belonging to the member countries of the OECD over the period 2000-2014, with a pooled linear
regression model and an individual and temporal fixed effects model (within).
To settle the debate on compactness / urban sprawl duality, we obtained that the population density
is associated with an increase in exposure to PM2.5 ambient pollution. The results for polycentricity
show an inverse relationship with PM2.5 exposure, which seems to confirm our assumption that polycentricity
could be a sustainable urban configuration favorable to the environment (reduction of
pollutant concentration), the economy (economic efficiency linked to a certain degree of urban compactness)
and human health (decrease in exposure).
Our model also allowed us to estimate the burden of air pollution for these 26 cities in OECD
countries with nearly 34,000 premature deaths per year for a total population of 115 million and an
economic cost estimated about nearly $ 135 billion in constant 2010 dollars a year.
Therefore, with more than 95% of the world’s population living in areas with a concentration of
particulate matter (PM2.5) that exceeds the WHO guidelines (HEI, 2018), the ’clean air’ challenge
is therefore more than ever one of the most important environmental challenges of the 21st century,
including in developed countries.