Bangalore among top polluted mega cities

From the sky, the Garden City of Bangalore now looks more smoggy compared to other mega cities in the subcontinent, thanks to rising levels of tiny soot particles in the atmosphere from vehicle and industrial pollution.

American and European mega cities appear cleaner over the past decade, while cities in China, India, the Middle East and Africa are worse, claims a new research by Israeli scientists who used data from three US satellites to study the world’s 189 largest cities, many of which house more than 10 million population.

They looked at aerosol concentration in the atmosphere, which serves as a potential indicator of man-made pollution because these tiny particles are emitted from fossil fuel combustion in factories, vehicles as well as from the burning of firewood, cow dung cake and other biomass.

The scientists looked at aerosol optical depth (AOD), which basically indicates the thickness of the aerosol cover over a city. The results came as shocker for South India.

“The increasing AOD trends over largest cities in the Indian subcontinent, the Middle East and North China can be clearly seen. By contrast, mega cities in Europe, the north-east of US and South-East Asia show mainly declining AOD trends,” the researchers from Tel Aviv University in Israel reported in the American Journal of Climate Change. With a 34 per cent average increase in atmospheric aerosol concentration between 2002 and 2010, Bangalore is among the worsening cities of the world. Hyderabad, Pune and Nagpur too fared badly.

Other Indian cities studied by Israeli researchers are Delhi, Mumbai, Kolkata, Chennai, Ahmedabad, Surat, Bhilai, Patna and Lucknow. All have significantly high aerosol levels in the atmosphere.

“The Israeli study is not showing pollution levels; but more on how it is changing. Mumbai and Delhi continue to be pollution hot spots. But, since the rate at which pollution is increasing is dependent more on how the city activities are growing, trends are larger in South India as these cities are growing quickly,” V Ramanathan, professor of climate sciences at the Scripps Institution of Oceanography at the University of California at San Diego, who is not involved with the Tel Aviv University study, told Deccan Herald.
In the Indian subcontinent, higher population density leads to an increase in the aerosol level, courtesy increased urbanisation.

Ramanathan, however, cautioned that changes in monsoon pattern as well as dust storm may also contribute to the trends, which need to be studied over a longer time frame.