NEW DELHI: Delhi has the most polluted air in the world. A World Health Organization (WHO) air quality database of 1,600 cities and 91 countries released on Wednesday shows that the concentration of PM2.5 (fine, respirable particles) is the highest in Delhi at 153 micrograms per cubic metre (g/m³) when the WHO standard is just about 10g/m³. The fine, particulate pollution which is considered most dangerous for health is way higher in Delhi compared with many other crowded Asian cities, including Beijing which has a PM2.5 level of 56g/m³, Karachi (117g/m³) and Shanghai (36g/m³).
The concentration of PM10 (coarse particles) in Delhi is about 286g/m³, more than 14 times higher than the WHO annual mean standard of 20. Peshawar (540g/m³) and Rawalpindi (448g/m³) in Pakistan fare worse on this parameter. Indian cities with a very high PM10 level include Gwalior, Raipur and Lucknow.
This is not the first time Delhi has earned the dubious distinction of having extremely polluted air. In January, Yale University's Environmental Performance Index 2014 had ranked India among the bottom five in a list of 178 countries for various parameters, including air pollution. A controversy erupted when the Yale data was interpreted to mean that Delhi's air quality is worse than Beijing's. The Delhi government and the ministry of earth sciences, which monitors air pollution data for the city, had vehemently denied this. But the latest WHO database suggests that Beijing probably has better control systems in place to deal with air pollution.
"WHO has not ranked cities but its database gives us an idea of where we stand. Delhi is more polluted than others. WHO has compared our annual mean levels with its standards, which are far lower than Indian standards. The database highlights what a major public health issue air pollution is and how aggressive our policies need to be," said Anumita Roychowdhury, air pollution expert with Centre for Science and Environment (CSE). India's annual mean standard for PM10 is 60g/m³ and for PM2.5 it is about 40g/m³.
High PM2.5 levels are associated with major health effects. WHO in its statement said: "High concentrations of small and fine particulate pollution is particularly associated with high numbers of deaths from heart disease and stroke, as well as respiratory illnesses and cancers. Measurement of fine particulate matter of 2.5 micrometres or less in diameter (PM2.5) is considered to be the best indicator of the level of health risks from air pollution".
Dr Maria Neira, WHO director for Public Health, Environmental and Social Determinants of Health said, "Cities such as Copenhagen and Bogota have improved air quality by promoting 'active transport' and prioritizing dedicated networks of urban public transport, walking and cycling".
Only 12% of the people living in cities get air quality conforming to WHO guidelines. About half of the urban population being monitored by WHO is exposed to air pollution that is at least 2.5 times higher than the levels the agency recommends.
