Delhi had more ‘clean air days’ in 2019 than four years ago: CSE report

The capital city had 50 per cent more days with ‘cleaner air quality’ in 2019, as compared with four years ago, with nearly 200 days when PM2.5 (particulate matter of size 2.5 micron) fell in ‘good’ to ‘moderate’ categories , according to a study carried out by the New Delhi based NGO Centre for Science and Environment (CSE).

PM2.5 also down

The CSE report Breathing Space : How to track and report air pollution under the National Clean Air Programme released early this week at an annual media conclave at Nimli in Rajasthan showed that the number of days that could fall in ‘good’, ‘satisfactory’ and ‘moderate’ categories has increased by nearly 50 per cent to 197 days in 2019 from 133 days in 2016. The analysis showed that the PM2.5 levels in Delhi has come down by 25-30 per cent over the last few years.

CSE experts, Anumita Roychowdhury and Avikal Somvanshi, came up with the report based on voluminous data available from the Central Pollution Control Board (CPCB).

“Even after a quarter drop, Delhi still needs cut of 65-75 per cent to meet its PM2.5 standards. Multi-sectoral action – closure of power plants and big industry, natural gas transition across sectors, phase-out of old vehicles, reduction in truck numbers, BS-VI fuels and BS-IV standards, and more, has bent the curve,” Roychaudhury said. But she said more disruptive action is needed for clean energy and technology transition, mobility transition and waste management to get the next big cut.

The report, however, pointed out major lacunae in air monitoring programme in the country.

Targets for cities

Last year, the government launched an ambitious programme called National Clean Air Programme (NCAP) which aimed at reducing particulate pollution in 122 highly polluted cities by 20 to 30 per cent by 2024 from the 2017 levels. Under NCAP, each of these cities is expected to cut their annual emissions by at least 6 per cent a year.

“The cities are expected to immediately begin reporting on their annual progress; but for that, they must know the methods and standard operating procedures for such reporting. How will cities know if their pollution levels are rising or declining,” asked Roychowdhury.

Currently, CPCB releases annual average of stations and spatial average for cities based on analysis of only manual air pollution monitors installed in different parts of these cities. While many cities have real-time monitors installed, data from these stations is not used for legal reporting.

Gaps in monitoring

“There is no explicit method for using real-time data – which is lot more continuous and voluminous than manual data – to establish a long term trend. Real-time data is used only for daily reporting of spatial averages against the national air quality index,” the report said. As a result, while the monitoring network expands for both manual and real-time monitors, cities were not explicitly told what monitors should be used, how data should be averaged and what geography they should represent.

The CSE analysis also showed that while it is mandatory to use manual monitors to record data for at least 104 days a year, as much as 73 per cent of monitoring stations do not meet this requirement. For instance, cities such as Kozhikode in Kerala and Vishakhapatanam in Andhra Pradesh do only 10 and 30 days of monitoring respectively.

Mukesh Sharma, a professor at the Indian Institute of Technology Kanpur, who has been studying air pollution for many years, said his team analysed sources of air pollution in the capital. During winter months, biomass burning was found to contribute to 26 per cent of Delhi’s pollution load, vehicles 25 per cent and another 30 per cent came from secondary particulates, which came from chemical reactions in the atmosphere caused by gaseous pollutants such as sulphur dioxide, nitrogen oxides and volatile organic compounds.

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