NEERI, IIT-Bombay: Air pollution at key traffic junctions alarming, says study

Alarmed by the findings, the Maharashtra Pollution Control Board (MPCB) has decided to install air purifiers at 33 traffic junctions in the city. The facility was inaugurated for three junctions last week.

According to the study, the main indicators to guage the level of contaminants in the air are the levels of Particulate Matter (PM) 2.5 and PM 10. While PM 2.5 indicates the extent of small pollutant particles released mainly from the exhaust of vehicles, the latter stands for slightly larger, coarser particles from windblown dust, road sweeping and construction.

While the permissible limits for PM 2.5 and PM 10 are 60 microgrammes per cubic metre (µg/m3) and 100 µg/m3, the study found that the existing levels at the traffic junctions were far worse.

The traffic junction outside Oberoi Mall in suburban Dindoshi, the scene of huge snarls during peak hours, was found to be the worst on these counts, with the PM 10 count at the site measuring 2709.25 µg/m3. The lowest PM 10 count, recorded outside Dadar’s Siddhivinayak Temple (596 µg/m3), was nearly six times above the permissible limit. In fact, the surveyors found that for the 19 out of 33 junctions surveyed, the pollution was more than 10 times the permissible levels.

Officials attributed the “heavy vehicular movement” on the northbound end of the Western Express Highway during peak evening hours to be one of the worst contributors to air pollution in Mumbai. Further, officials fear that with the construction work of Metro along the same stretch underway, the traffic and the pollution count will worsen further.

Currently, Mumbai’s overall air quality levels is recognised as ‘very poor’, according to SAFAR. Mumbai’s Air Quality Index (AQI) is recorded by the System of Air Quality and Weather Forecasting and Research (SAFAR), which is run by the Indian Institute of Tropical Meteorology with the support of India Meteorological Department. On Saturday evening, Mumbai’s AQI was more than 300 µg/m3, the worst area recorded was Mazgaon with 345 µg/m3.

The joint air pollution study further revealed that a high percentage of toxic matter released from vehicles had accumulated near the junctions.

Officials said the 33 congested traffic junctions were selected based on several factors such as location of the site, vehicular congestion, pedestrian movement and construction in the area. The sampling time of the survey was during peak-hour time of the junctions and they were all surveyed last year before and after the 2016 monsoons.

WAYU (Wind Augmentation and Air Purifying Unit), that are currently operational in Kalanagar, Sion and Ghatkopar junctions, is an active air pollution mitigation technology that works on the principle of breaking down carbon monoxide, officials said. The gadget WAYU was created in a joint collaboration between NEERI and IIT. More WAYU devices are proposed to be set up in the other 30 traffic junctions in the city.

Each of the WAYU devices has filters attached with a thermal oxidiser to separate the toxic content from the air, which is then released back into the atmosphere with the help of a fan. There area air quality sensors have been used to assess efficiency of the devices and the efficiency of the devices is expected to purify 40-60 per cent of the air it processes, officials said.