World Wide Air Pollution in the Future

What is the world wide trend in air pollution? On the surface North America and Europe have been gradually improving. However, that is due to often moving industry to other countries such as China or India where air pollution is a bit more of a problem. Most of the world's population will be subject to degraded air quality by 2050 if human-made emissions continue as usual. In this business-as-usual scenario, the average world citizen 40 years from now will experience similar air pollution to that of today's average East Asian citizen. These conclusions are those of a study published August 1 in Atmospheric Chemistry and Physics, an Open Access journal of the European Geosciences Union (EGU). Air pollution is a major health risk that may worsen with increasing industrial activity. At present, urban outdoor air pollution causes 1.3 million estimated deaths per year worldwide, according to the World Health Organization.

The atmospheric chemistry general circulation model EMAC was used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies. This scenario is chosen to show the effects of not implementing legislation to prevent additional climate change and growing air pollution, other than what is in place for the base year 2005, representing a pessimistic (but plausible) future.

To identify possible future hot spots of poor air quality, a multi pollutant index (MPI), suited for global model output, was applied. It appears that East and South Asia and the Middle East represent such hotspots due to very high pollutant concentrations, while a general increase of MPIs is observed in all populated regions in the Northern Hemisphere.

In East Asia a range of pollutant gases and fine particulate matter (PM2.5) is projected to reach very high levels from 2005 onward, while in South Asia air pollution, including ozone, will grow rapidly towards the middle of the century. Around the Persian Gulf, where natural PM2.5 concentrations are already high (desert dust), ozone levels are expected to increase strongly.

The population weighted MPI (PW-MPI), which combines demographic and pollutant concentration projections, shows that a rapidly increasing number of people worldwide will experience reduced air quality during the first half of the 21st century. Following this business as usual scenario, it is projected that air quality for the global average citizen in 2050 would be almost comparable to that for the average citizen in East Asia in the year 2005, which underscores the need to pursue emission reductions.

"At present the post-Kyoto climate negotiations are progressing slowly, and it is unclear how air quality policies will develop globally," explains co-author Greet Janssens-Maenhout of the European Commission Joint Research Centre in Italy. "In regions with economic growth, it might be less effective to implement emission-reduction measures due to strong growth in activities in particular sectors; in countries suffering from the economic downturn, implementing expensive air-quality measures could prove difficult in coming years," she adds.

Air pollution would increase in Europe and North America, but to a much lesser extent than in Asia, due to the effect of local mitigation policies that have been in place for over two decades.

The results show that in 2025 and 2050, under the business-as-usual scenario studied, East Asia will be exposed to high levels of pollutants, such as nitrogen dioxide, sulfur dioxide and fine particulate matter (PM 2.5. Northern India and the Arabian Gulf region, on the other hand, will suffer a marked increase in ozone levels.

The analysis now published is the first to include all five major air pollutants know to negatively impact human health: PM 2.5, nitrogen dioxide, sulfur dioxide, ozone, and carbon monoxide. The scientists considered pollutants released through human activity, as well as those occurring naturally such as desert dust, sea spray, or volcanic emissions.

Taking all pollutants into account, eastern China, northern India, the Middle East, and North Africa are projected to have the world's poorest air quality in the future. In the latter locations this is due to a combination of natural desert dust and man-induced ozone. The effect of anthropogenic pollution emissions are predicted to be most harmful in East and South Asia, where air pollution is projected to triple compared to current levels.

For further information see Article or Pollution.

Multipollutant Index image via MPI for Chemistry.