State of the Planet

News from the Columbia Climate School


The Changing Face of Air Quality

Map showing exposure to fine-particulate matter from 1999-2011
Improved air quality between 2011 and 1999 can be seen over North America and Europe, driven by cleaner technologies adopted there—but India and China show an increase in exposure to fine-particulate matter, due largely to industrial expansion.

Fine-particulate matter represents one of the most serious types of air pollutants, and is of particular concern in many parts of Asia. For example, for 2010–2012, an estimated 70% of people were living with air quality associated with high mortality risks, according to the World Health Organization Interim Target-1. This is an increase from 51% in 1998–2000.

A recent data release, Global Annual  Grids, offers insights into the extent of global human exposure to fine particulate matter (PM2.5) over more than a decade. These satellite-derived estimates of PM2.5 provide one of the few ways of assessing changes in exposure to air pollution around the world over the long term. By looking at regional differences between PM2.5 concentrations at the beginning and end of the data set, ranging from 1998 through 2012, we can get a sense of the changing face of air quality throughout the world.

In the map above, improvements between 2011 and 1999 are visible over North America and Europe, driven by cleaner technologies adopted in these regions. India and China, by contrast, show an increase in PM2.5 over this time period, due largely to industrial expansion. Natural changes may also play a role, with increasing concentrations in the Middle East being associated with changing patterns in mineral dust emissions from the Sahara Desert.

These global grids of estimated PM2.5 surface concentrations are useful in health and environmental research, for example, as a valuable input to the World Health Organization (WHO) global burden of disease study. The grids were developed by Aaron van Donkelaar and colleagues at Dalhousie University in Canada. The new data set replaces an earlier one released by the NASA Socioeconomic Data and Applications Center operated by CIESIN and features improved accuracy, a longer time span, and higher spatial resolution than the previous version. More details can be found in the van Donkelaar et al. 2015 article, “Use of Satellite Observations for Long-Term Exposure Assessment of Global Concentrations of Fine Particulate Matter,” in the journal Environmental Health Perspectives.


The PM2.5 : Change in Concentration map was made by CIESIN geographic information specialist Tricia Chai-Onn.

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