MPCB report out: Did Mumbai really breathe easy in 2019-20?

The concentration of oxides of nitrogen (NOx) and respirable suspended particulate matter (PM10) in 2019-20 was the lowest in 11 years, an annual report by the Maharashtra

The concentration of oxides of nitrogen (NOx) and respirable suspended particulate matter (PM10) in 2019-20 was the lowest in 11 years, an annual report by the Maharashtra Pollution Control Board (MPCB) has revealed.

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According to the Air Quality Status Report 2019-20, PM10 concentration fell from 178 micrograms per cubic metre (µg/m3) in 2009-10 to 121 µg/m3 in 2017-18, 129 µg/m3 in 2018-19, and 95 µg/m3 in 2019-20. Likewise, NOx levels fell from 99 µg/m3 in 2009-10 to 75 µg/m3 in 2018-19 and 47 µg/m3 in 2019-20. The report has revealed that Mumbai’s NOx levels declined by 37%, while the PM10 level dropped by 26% from last year.

Meanwhile, PM2.5 levels – tiny pollutant particles of 2.5 micron size that are most dangerous – were below permissible limits across all the 11 real-time ambient air quality monitoring stations in Mumbai in 2019-20. The annual sulphur dioxide (SO2) concentration in the city ranged within 7 µg/m3 and 16 µg/m3, far below the annual limit of 50 µg/m3.

PM10 pollutants, which are solid and liquid particles, pose a great risk to human health as they can enter deep into the lungs during respiration and some may even reach the bloodstream. NOx pollutants, which are majorly caused due to vehicular emissions, lead to reduced lung function and oxygenation of body tissues.

“With the focus being laid on tighter emission norms, enhanced monitoring, on-ground implementation of directions issued by MPCB, adherence to directives under the action plan, and several awareness programmes focused towards achieving clean air, Mumbai has managed to address specific emission sources that led to a decline in PM,” said VM Motghare, joint director (air quality), MPCB.

“However, a lot more needs to be done to bring the levels below safe limits and the recent funds sanctioned by the Centre (₹244 crore) will help in achieving this.”

Though the year-on-year air quality trends have shown positive trends in PM10 and NOx levels for the entire city, location-specific levels across 11 stations in Mumbai revealed that PM10 pollutant levels were above permissible limits in 2019-20 in every station, while nine stations had unsafe limits for NOx.

The area around the international airport in Sahar, Andheri, had the worst NOx concentration (87 µg/m3) across Maharashtra, followed by Sion and Kurla at 79 µg/m3 and 76 µg/m3 respectively.

“Necessary steps, especially towards curbing vehicular emissions, are being undertaken to mitigate the issue of NOx pollution,” said Motghare.

For PM10, highest levels were recorded at Kurla (140 µg/m3) followed by Sion (117 µg/m3), Sahar (116 µg/m3), and Mulund (103 µg/m3). The remaining stations recorded concentration in the range of 64 µg/m3 and 98 µg/m3. The safe limit for PM10 is 60 µg/m3.

In Mumbai, all observations were made from April 2019 to March 2020 where MPCB analysed the air quality index (AQI) range for the period for 11 monitoring stations. MPCB categorises AQI levels in the 0-50 range as good; 51-100 as satisfactory; 101-200 as moderate; 201-300 as poor; 301-400 as very poor and above 400 as severe. Overall areas around Kurla, Sion, the airport, Bandra and Sion were most polluted in 2019-20.

Very poor AQI was observed only at Bandra (one day) and Sion (six days) during 2019-20. Poor AQI was reported for most observations at Kurla (19%), followed by airport area (14%) and Sion (13%). Moderate AQI was observed at Kurla and Mulund for more than 50% observations, while Powai, Sion and Vile Parle recorded around 30% observations. Worli and Colaba recorded 35% moderate AQI observations. Good AQI was recorded for only 21% of total observations in Mumbai with maximum good air days at Borivli (43%) and minimum at Kurla (3.8%).

Independent experts who studied the report said that the analysis indicated that Mumbai still needed stringent action to control NOx and PM, and bring them to safe annual average limits.

“Overall, the pollution curve peaks during November to February when the monthly averages of PM and NOx levels go above the indicative annual standards,” said Anumita Roy Chowdhury, executive director (research and advocacy), Centre for Science and Environment, Delhi.

She added that the rise in NOx indicates the impact of increasing traffic and motorisation, even as the overall annual PM2.5 was lower than the standards though the monthly averages increase during winter.

“It is not clear how the ratio between PM10 and PM2.5 is changing over time. However, the analysis indicates that Mumbai will require stringent time bound action on vehicles and public transport, construction activities, industrial units, waste management and solid fuel use for cooking. This data is on ambient concentration which is greatly influenced by the sea breeze. But local exposures are expected to be high and that requires mapping of hotspot pollution and action,” said Chowdhury.

PM 10 concentration for Mumbai – annual average

2009-10 – 178 µg/m3

2017-18 – 121 µg/m3

2018-19 – 129 µg/m3

2019-20 – 95 µg/m3

NOx concentration for Mumbai – annual average

2009-10 – 99 µg/m3

2017-18 – 60 µg/m3

2018-19 – 75 µg/m3

2019-20 – 47 µg/m3

Most-polluted locations in the city

For PM 10 – 60 µg/m3 (annual safe limit)

Kurla - 140 µg/m3

Sion – 117 µg/m3

Mumbai international airport – 116 µg/m3

For NOx – 40 µg/m3 (annual safe limit)

Mumbai international airport - 87 µg/m3 (Also highest in state)

Sion – 79 µg/m3

Kurla – 76 µg/m3

(Source: Air Quality Status Report 2019-20)

Important report findings for Maharashtra

There are 23 real-time air monitoring stations in Maharashtra

Nine stations in Maharashtra (up from six in 2018-19) – Aurangabad, Kalyan, Kolhapur, Mumbai, Navi Mumbai, Nagpur, Pune, Raigad and Thane – recorded annual average NOx concentrations which were higher than the prescribed annual average limit

17 stations in Maharashtra recorded PM10 levels above safe limits. Chandrapur (Ghuggus -204 µg/m3, Rajura – 171 µg/m3), Thane (Kopri – 154 µg/m3, Naupada – 153 µg/m3, Balkum/Glaxo – 140 µg/m3) were the most-polluted locations for PM10 pollutant

PM2.5 concentration for all the 23 locations was below safe standards (40 µg/m3). Kalyan and Karve Road, Pune, recorded annual average PM2.5 concentrations at 40 µg/m3

Ozone pollution showed Chandrapur, Kalyan, Mahape, Mulund and Nagpur had higher concentrations than the safe limit of 100 µg/m3

For benzene pollution, 11 locations Bandra, Colaba, Dombivli, Mahape, Nagpur, Nashik, Nerul, Kalyan, Kurla, Sion and Worli recorded concentration above the safe limit (5 µg/m3) during several intervals in 2019-20

Bandra, Dombivli, Nagpur, Kalyan and Solapur exceeded the eight-hour safe concentration for carbon monoxide (CO) standard of 2 µg/m3.

(Source: Air Quality Status Report 2019-20)