Calcutta's ubiquitous taxis are responsible for much of the city's air pollution, and many have yet to make the change over to more environmentally fuels. (Picture by Amit Kar)
Much of the city's population of 18m people cannot escape traffic jams in which vehicles like this belch out smoke.
Because Calcutta is often swathed in smog, people who take exercise are often more at risk of suffering some form of respiratory complaint .
A shortage of public transport often results in people using pollution-emitting auto rickshaws and taxis, which often compete for road space.
People who work in the open air - such as these street sellers - are thought to be especially at risk from air pollution, along with rickshaw pullers and policemen.
Poor air quality is bad news for children of the city, and critics say that government inaction over the issue only makes matters worse for youngsters who live close to main roads.