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‘Dirtiest’ tag off Delhi but worries remain

New Delhi, May 9: The World Health Organisation today distanced itself from suggestions that it had earlier this week portrayed Delhi as having the worst air quality among 1,600 cities worldwide, after Indian scientists said the agency’s database could not be used to compare cities or countries.

The WHO released its Ambient Air Pollution report for 2014 on Wednesday. It shows Delhi and several other Indian cities as having air pollution levels — measured in terms of fine, inhalable particulate matter (PM) in the air — far exceeding the limits for risks to human health.

Using figures from India’s Central Pollution Control Board, the report has listed Delhi’s average levels of PM2.5 — particles smaller than 2.5 microns — at 153 micrograms per cubic metre last year, the highest among any city covered in the survey. The safe upper limit for PM2.5 is 40 micrograms per cubic metre.

Scientists tracking air quality trends in India said the Ambient Air Pollution database could not be used to compare air pollution levels between different countries because it did not use average air pollution figures from the same year in all the 91 countries monitored.

For example, the air pollution figures for Accra in Ghana are from 2008, those for Beijing from 2010, those for Durban in South Africa from 2012, those for Delhi from 2010 and 2013, those for Calcutta from 2009-10, and those for Patna from 2011 and 2013.

“There is absolutely no doubt that Delhi’s air quality is poor, but to use the WHO report to portray Delhi as having the worst air in the world is misleading,” said Gufran Beig, a senior scientist at the Indian Institute of Tropical Meteorology, Pune.

A WHO spokesperson said today the database was intended to “promote awareness” about air pollution worldwide and generate discussions on steps to tackle a problem that has widespread health consequences.

“We have not issued any ranking at all,” the Geneva-based spokesperson told The Telegraph over the phone. “We’ve only released a database based on national figures.”

The WHO report shows that several Indian cities have had levels of both PM2.5 and PM10 (the latter denoting particles between 2.5 and 10 microns) exceeding safety limits, with Chennai the exception. The safe limits for PM10 is 60 micrograms per cubic metre. (See chart)

“This is a fresh reminder of India’s extremely poor air quality,” said Anumita Roychowdhury, head of the clean-air campaign at the Centre for Science and Environment, a non-government organisation in Delhi.

“India needs urgent action to leapfrog vehicle technology and fuel quality, scale up public transport, reduce dependence on cars, and promote walking and cycling,” she said in a statement.

A research study published last year estimated that about 14,000 people in Calcutta and 17,000 people in Delhi die prematurely each year from cardiovascular and respiratory diseases as well as lung cancer associated with air pollution.

But some scientists are also questioning the reliability of the Delhi figures in the WHO database, saying they appear inconsistent with the results of an independent air quality-monitoring programme supported by India’s earth sciences ministry.

A city’s representative air pollution figures should, they said, be averaged from multiple monitoring sites strategically located to represent all the micro-environments in that city such as residential localities, industrial areas, and busy traffic junctions.

The ministry initiative has installed 10 such monitoring stations in Delhi as part of a broader effort to develop India’s first air pollution forecasting system.

The average PM2.5 values in Delhi from 2011 to 2013 range between 105 to 110 micrograms per cubic metre, Beig said. The value of PM10 was 205 in 2012 and 197 in 2013.

These figures, Beig said, are significantly lower than Delhi’s air pollution figures in the WHO database — 153 for PM2.5 and 286 for PM10.

“They appear biased towards sites with higher air pollution,” he told this newspaper.

But Rowchowdhury said the Central Pollution Control Board data, used in the WHO report, were the national standard for tracking air quality.

“In any case, why quibble over such differences? Even the Indian Institute of Tropical Meteorology numbers far exceed the safety limits,” she told this newspaper. “We need actions quickly.”

A report generated by a team of researchers at Yale University and released in January this year had ranked India’s air quality, measured in terms of PM2.5, at 177 among 178 countries with China in the last position.