Sunday, October 02, 2016

Kolkata Ranked 4th Worst Polluted City

Coarse dust particles - a byproduct of construction activities - have made Kolkata the fourth most polluted ‘megacity’ in the world, a recent report published by the World Health Organization (WHO) claims. While the report has placed Delhi at the top of the list, Cairo and Dhaka occupy the second and third positions respectively. Kolkata comes fourth just ahead of Mumbai. Read more @ Hindustan Times and track pollution in your city with this real-time air quality map

According to the report the PM10 level in Kolkata during this pseriod was nearly seven times the limit prescribed by WHO. If one considers the Indian safety limits, which is less stringent, Kolkata’s PM10 pollution level is more than double. These particles can cause asthma attacks, aggravate bronchitis and other lung diseases, and reduce the body’s ability to fight infections, said doctors. The report is based on the presence of such particles in the air of the city between 2011 and 2015. This list was prepared solely on the basis of PM10 level, and other pollutants such as PM2.5, NOx, SOx, CO2 etc were not included. If all Indian cities are taken into account the Gwallior reported the highest pollution. (But it is not a megacity.)

While the city’s PM10 level soared to around 140 micrograms per cubic metre, the WHO’s safety limit for this coarse pollutants is not more than 20 micrograms per cubic metre. The Indian safety limit is 60 micrograms per cubic metre. Delhi which has been ranked as the most polluted megacity has PM10 level as high as 240 micrograms per cubic metre. Mumbai which ranks fifth has PM10 level around 120 micrograms per cubic metre. The WHO report also suggests that the PM10 level in Kolkata was just around 100 micrograms per cubic metre in 2009-2010. So what forced the level of dust particles to shoot up?

Chatterjee added that another source of PM10 in Kolkata is the westerly winds that come in from the west and north India during the winter. They bring the dust particles from neighbouring and far flung states including Delhi, UP, Bihar and Jharkhand, raising pollution levels during winter months. Though physicians and scientists claimed that it is the PM2.5 – the finer particulate matter measuring less than 2.5 micros – which are more deadly, they also pointed out PM10 is also bad enough to cause damage and trigger a variety of pulmonary diseases as they can can penetrate deep into the lungs.


This is modeled air quality for India in forecast mode. The reports for all the 640 Indian districts everyday @ India Air Quality.Info

See what is happening at the regional scale, which is conducted as part of the all India air pollution forecasting program, hosted @ The animation below is from a WRF-CAMx simulation conducted @ 0.25x0.25 degree resolution (approximately, 25km x 25km).

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