Asia joins West as major air polluter

A 400,000 square mile, or one million sq km, plume of pollution now covers much of the Northern Indian Ocean every winter, taking Asia into the major league of air polluters.

The giant pall of soot and toxic gas almost double the size of France is largely caused by agricultural and domestic fires, says a new study by the Indian Ocean Experiment (INDOEX), reported in 9 February’s edition of Science. Researchers from INDOEX, an international field experiment in the Indian Ocean, which aims to investigate the severity of air pollution from Asia, says that the study suggests that Asia is moving up to join its western neighbours in the big league of global air polluters.

Owing to the fact that the atmosphere over the Indian Ocean is cleaned by monsoon rains moving north during the summer, the clean summer atmosphere can be compared with polluted air brought south into the region when the monsoon air-currents reverse in the winter. “The winter monsoon provides an excellent natural laboratory,” explained Jos Lelieveld, an atmospheric scientist at the Max Planck Institute for Chemistry in Mainz, Germany, who worked on INDOEX, which utilised aircraft, research vessels and a measuring station in the Maldives with satellite data to analyse the pollution plume.

Evidence of the importance of soot and organic particles, collectively known as aerosols, in climate change has just emerged (see earlier story) and researchers will use data from INDOEX to update models that predict global and regional climate change. In this study, largely due to the blanketing effect of aerosols warming the atmosphere instead of allowing heat from the sun to reach the ocean’s surface, 10 to 20% less heat arrives at the Indian Ocean during the winter monsoon, researchers believe.

Some parts of Asia, especially India, may have to worry about carbon monoxide too. “Low temperature combustion produces large amounts of carbon monoxide,” Lelieveld said. Besides its own toxic effect, carbon monoxide also removes air-cleaning hydroxyl radicals from the atmosphere. Without these, air pollution can persist for much longer, exacerbating its effects.

The World Health Organization recently said that in India, where 80% of households use solid fuel, there are estimates that half a million children die annually from indoor air pollution, especially from acute respiratory infections (see related story).

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