Delhi’s annual average nitrogen dioxide level way beyond safe limit since 2013: Report

New Delhi: Delhi has not been able to meet the CPCB’s annual average safe limit of nitrogen dioxide – 40 micrograms per cubic metre – since 2013, according to a new analysis by air pollution policy tracking platform NCAP Tracker.

From 2013 to 2020, Delhi’s average annual NO2 levels ranged from 61 micrograms per cubic metre to 73 micrograms per cubic metre.

The capital recorded an annual average NO2 concentration of 61 micrograms per cubic metre in 2020, the lowest in the last eight years.

This shows that despite the complete nationwide lockdown which halted all transport, industrial activity and many other NO2 emitting sources for three months, the year’s average could not be anywhere close to the Central Pollution Control Board (CPCB) safe limit of 40 micrograms per cubic metre.

Nitrogen oxides are a family of toxic, highly reactive gases which form when fuel is burned at high temperatures. NOx pollution is emitted by automobiles, trucks and various non-road vehicles like construction equipment, boats, etc.

Industrial sources of NOx are essentially fossil-fuel-based power plants, incineration plants, wastewater treatment facilities, glass and cement production facilities and oil refineries.

Delhi recorded a gradual increase in average annual NO2 levels from 2015 to 2018, with 2018 and 2019 recording 73.66 micrograms per cubic metre and 71 micrograms per cubic metre, respectively.

The analysis also revealed that NO2 emission reduced significantly (by up to 290 per cent) during the Covid lockdown period from March 25 to April 30, 2020, compared to the same period in 2019 due to the reduced operating capacity of the thermal power plants in areas surrounding Delhi.

During the lockdown, the NO2 in the city outflow was also significantly reduced due to restrictions on traffic movement.

An analysis of the monthly average nitrogen dioxide levels for all 40 monitoring stations in Delhi established that 25 locations in the national capital recorded NO2 concentration above the safe limit of 80 micrograms per cubic metre in November.

Anand Vihar – one of the 13 pollution hotspots in Delhi – recorded a monthly average NO2 concentration of 131 micrograms per cubic metre in November this year.

“Clearly local sources like the Inter-State Bus Terminus, the Ghazipur landfill site and the NH24 highway in the area are transporting emissions from heavy vehicles and other sources to this monitoring site,” the report said.

Dr Karni Singh Shooting Range recorded133 micrograms per cubic metre NO2 monthly average levels.

More locations that recorded November averages for NO2 levels in triple digits are East Arjun Nagar (125), IGI Airport (111), Dilshad Garden (105), Jawaharlal Nehru University (109), Nehru Nagar (108) and Pusa Road (114).

These levels are also juxtaposed with parts of the city with much lower NO2 levels, like CRRI Mathura Road (19), North Campus (5), Siri Fort (10) and Lodhi Road (15).

Prof SN Tripathi, Steering Committee Member, National Clean Air Programme, said: “NOx is showing an increasing trend in different cities of the country and particularly for Delhi-NCR. Daily exceeding values for any particular period of time, and overall average levels in NCR indicate that NOx values are far greater than annual safety limits prescribed by CPCB, leading to both short term and long term exposure to people.

“This can have serious health implications. Therefore, these need to be urgently looked into and corrective and mitigative measures need to be taken so that NOx values can be brought within control in Delhi NCR and other parts of the country.”

Dr Arun Sharma, Director, National Institute for Implementation Research for Non-Communicable Diseases, said: “NO2 as a gas has not so serious effects on the health of the people but its secondary effects through an increase in PM2.5 concentrations and augmentation of ozone formation are a matter of concern.”

The maximum concentration is seen either in densely populated urban areas or those with a heavy concentration of industries, where habitation in poorly ventilated low-income housing is predominant, he said.

Aarti Khosla, Director, Climate Trends, said focusing on such information should allow state governments, the Centre and citizens to know where to act.

“Having year-long above-average concentrations of nitrogen dioxide which is evident in busy traffic or high-density industrial areas shows where action should be,” she said.


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