Vehicles are a major source of pollution in Bengaluru

BENGALURU: Official claims that Bengaluru’s air quality is improving may have to be taken with a pinch of salt. Raising doubts over the accuracy of official air quality index (AQI) statistics and terming them misleading, a recent study says monitoring stations set up by central and state pollution control boards are located at altitudes higher than what’s ideal for collection of data.

“Vehicles account for around 40% of the particulate matter (PM) in Bengaluru’s atmosphere. Dispersion of PM in air is heavily influenced by three factors — number of vehicles, wind and availability of open spaces. So, the ideal place to locate collection points is not more than five metres from the road surface,” said Shishir Suresh, a research student in mathematical physics at University of Pécs in Hungary. He conducted the study in association with Bramhi Panamalai, who holds a masters in communication and media studies degree with an exchange study in Volda University College, Norway.

Monitoring stations in Bengaluru are mostly on skyscrapers and tall buildings, Shishir said. “As there is more PM dispersion at higher altitudes, this may lead one to believe that the air is cleaner than it is. This means most measurements from these stations are misleading,” he explained.

The duo conducted the study when they were in the city for a break and submitted their findings to the government a few months ago.

As per the revised action plan for controlling air pollution, recently prepared by Karnataka State Pollution Control Board ( KSPCB ), the city’s air quality has been improving over the years. Board officials said daily average AQI dropped from 107 in 2014-15 to 88 in 2018-19. Lower AQI indicates lesser pollution.

More stations needed

With Bengaluru not having as many air quality monitoring stations as required, the figures only get more skewed, the study observed.

There are 13 manual monitoring stations and seven real-time continuous ambient air monitoring stations (CAAMS) in the city. “It’s like using a single toothbrush for the whole family; it just can’t last. PM meters are sophisticated monitors consisting of sensors and actuators, which need to be calibrated from time to time. Since they are not maintained properly, data collected may be skewed,” pointed out Shishir.

The researcher duo collected data from sources like central and state pollution control boards, open AQI, NASA and WHO and consolidated it for the study.

Station set up at prescribed height: KSPCB

A senior official from KSPCB said monitoring stations have been set up at the prescribed height of six metres. Asked about vehicular emissions and the need to monitor quality of air in people’s breathing zone, the official said they have mobile monitoring stations to collect the said data. “In fact, Karnataka was one of the first to deploy mobile stations, which collect data at a height of 1.5 metres. However, I agree that we don’t have enough monitoring stations. We’re in the process of setting up more centres,” he added.

What is particulate matter

Particulate matter comprises particles suspended in the air — they may be in solid or liquid state or a complex mixture of both. Together, they are hazardous to humans when ingested or inhaled or when they come in contact with hair or skin. PM is measured in two sizes: up to and lesser than 10 microns, and 2.5 microns.

