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Updated: Jun 23, 2019 01:14 IST

Despite the Maharashtra Pollution Control Board (MPCB) claiming levels of particulate matter (PM) have declined in Mumbai, data released on Friday shows the city’s level of PM 10 in 2018 was the highest in over 20 years. On Friday, data gathered by the Central Pollution Control Board (CPCB) was released in the Lok Sabha by the Union environment ministry.

According to the CPCB, PM 10 and PM 2.5 levels in Mumbai have been steadily increasing.

Data from the environment ministry showed the annual average of PM 10 levels in Mumbai were 166µg/m3 in 2018 and 151µg/m3 in 2017. The annual safe limit for PM 10, according to the CPCB is 60 micrograms per cubic metre (µg/m3). The third highest in two decades was recorded in 2008 (127µg/m3).

A sharp drop in particulate pollution was recorded in 2001 when levels fell to 67.2µg/m3 while in 1999, they were at 115µg/m3. PM2.5 levels, which are being measured since 2015, were also the highest in 2018 for Mumbai. Levels of sulphur dioxide (SO2) and nitrogen oxide (NOx) levels were within limits (see box).

PM 10 and 2.5 are solid and liquid pollutants of less than 10 and 2.5 microns in size respectively and are suspended in air. These particles can enter the respiratory system and cause health complications. “Current levels may not impact on a daily basis, but may lead to chronic health ailments over a decade of exposure,” said a CBCB official.

“There is an overall increasing trend for PM10 and PM2.5 in Mumbai despite having the advantage of the sea breeze,” said VK Shukla, in-charge of air quality management, CPCB. “As of now, vehicular and industrial emission, construction dust and solid fuel emissions are the highest threats. Mitigation measures for all sources have been addressed under the air pollution action plan for Mumbai. The plan has been approved by CPCB and is already under implementation by the state.”

The environment ministry’s data contradicts the MPCB’s claim on World Environment Day (June 5) that there has been a 6% decline in PM2.5 levels and 9% decline in PM10 levels in 2018-19 from 2017-18, across major cities in Maharashtra including Mumbai.

Annual average PM10 data in Mumbai, according to the System of Air Quality Weather Forecasting and Research (SAFAR), was 110µg/m3, 56µg/m3 lesser than the Centre’s data. SAFAR monitors air quality across 10 stations in the city. The environment ministry’s data is based on data recorded by MPCB, from two stations in Sion and Bandra.

PM10 levels for other cities in Maharashtra, such as Pune, Nagpur, Nashik and Aurangabad, all witnessed an increasing trend. Thane was the only city that recorded a decreasing trend.

“The rise in PM is a concern, but we are trying to understand the exact location of monitoring stations and whether there is any site specific aberration which is getting captured as city data or whether it is a city-wide phenomena,” said Sudhir Shrivastava, chairman, MPCB.

“Mumbai’s action plan has already been initiated focusing on broad objectives. Reduction of private vehicles with planned introduction of cleaner fuels, increasing public transport, reducing resuspension of windblown dust from construction and demolition waste, and distributing more liquefied petroleum gas (LPG) connections to slum areas are some of the examples,” he said.

Experts said had Mumbai been landlocked and not had the advantage of swift dispersion of pollutants through its sea breeze, pollution levels would have significantly higher.

“The rising air pollution trend is a clear indicator that monitoring and enforcement are not being balanced. To curtail this rise, fossil fuel consumption has to be restricted at source and regulating industries by implementing stricter emission standards,” said Sunil Dahiya, campaigner, Global Air Pollution unit, Greenpeace.