Combining observational data, atmospheric chemistry models at different spatial scales, and comprehensive emission inventories of the various precursor emissions, IIASA analyses clearly demonstrate that even in street canyons the dominating contribution to harmful human exposure to fine particulate matter (PM2.5) emerges from more distant sources, often located several hundreds of kilometers away.

This calls for a fundamental reorientation of conventional air pollution control strategies around the world. In contrast to present policy approaches that attempt to improve urban air quality through local (traffic management) measures at the city scale, the new findings highlight the need for regionally coordinated action involving all sources of precursor emissions in a wide range of economic sectors.

In particular, a substantial fraction of PM2.5 (typically 20-40% in European cities, and even more in developing countries) originates from solid fuel combustion (i.e., biomass and coal) in households for heating and cooking purposes. Effective policies to reduce pollution from these sources will not only result in significantly reduced health impacts from lower outdoor and indoor exposure to fine particulate matter but, by providing access to cleaner forms of energy, will also improve the living conditions of the poorest. At the same time, such measures will also significantly reduce emissions of black carbon and other short-lived climate pollutants, which will have positive impacts on temperature increase in the near term.

In addition, chemical analyses clearly demonstrate that secondary inorganic aerosols constitute typically 40-50% of the observed mass of PM2.5 in urban areas, both in Europe and Asia. These are formed in the presence of ammonia (NH₃), which is mainly released from agricultural sources. In many conditions, the availability of NH₃ will determine the formation of these particles, and effective reductions of these secondary aerosols cannot be achieved without clear cuts in agricultural ammonia emissions. This chemical mechanism provides further rationales for controlling nitrogen emissions, in addition to the other implications of the serious disturbance of the nitrogen cycle. A wide range of pollution control options at rather modest costs is readily available

Research Projects

Pollution Management and Environmental Health
(PMEH)

Pollution is becoming an increasingly significant development challenge causing currently about 16% of all deaths worldwide with the poor, marginalized, and young hardest hit by the health effects of the contamination. More

Complex Urban Systems for Sustainability and Health (CUSSH)

The Complex Urban Systems for Sustainability and Health (CUSSH) is a four-year Wellcome Trust funded project that will deliver key global research on the systems that connect urban development and health. Alongside partner cities in France, China and Kenya the project will assist decision-makers and the public about areas of development that afford the greatest opportunities for health and sustainability.  More

Atmospheric Aerosol Chemistry and Climate Change (PEGASOS)

The goal of PEGASOS is to enhance our understanding of the interactions of climate and atmospheric chemistry in the past, present and future. More

Key Findings

• Even the largest cities cannot solve their air pollution problem without regional cooperation

Last edited: 20 June 2018