Bengaluru air pollution study raises concerns of personal exposure risk

KSPCB terms data 'incorrect'

A new independent study that focused on Bengaluru’s air quality, by recording data on seven arterial roads over a week, has revealed that Bengaluru’s air quality, during peak hours of traffic, is comparable to some of the most polluted cities in the world. 

The study by Climate Trends monitored the breathable air quality level or Personalised Exposure (PE) to particulate pollutants PM2.5 and PM10 levels during peak traffic time (morning and evening) for seven days, from Feb. 5 to Feb. 15, for commuters travelling on seven arterial roads, including Jayanagar/Banashankari, Silk Board, Electronics City, Whitefield, Uttarahalli, M.G. Road and Mehkri Circle.
 
The study was conducted using an autorickshaw that was fitted with a GPS tracker and a calibrated low-cost monitor that measured Particulate Matter (PM), also known as particle pollution.

The study said that, according to KSPCB data, PM2.5 values have exceeded the National Ambient Air Quality Standards (40.0 μg/m3) by 3% to 45%, at all nine locations, due to vehicular traffic increase and construction activities.
 
The PM10 values have also exceeded the National Ambient Air Quality Standards (60μg/m3) by 30% to 120% at all the 15 locations except at Saneguruvanahalli.

KSPCB measures ambient air quality and monitoring stations are placed three to 10 metres above ground level, away from direct air pollution sources.
 
The Climate Trends study looked at peak personalised exposure -- PM2.5 measured as high as 200 μg/m3 at New Tharagupet, which is way above the 40 μg/m3, the CPCB limit for a 24-hour average.
 
Speaking to DH, Aishwarya Sudhir, an environmental researcher behind the study, said that it is important to be cautious and not sensationalise the findings. She clarified that the national and international standards are based on 24-hour averages, and this study averaged just four hours every day for 15 days and therefore the two cannot be directly comparable.
 
She stated that the device used for the study, which focused on the breathable air quality level or personalised exposure, consistently generated averages above 200 micrograms per cubic metre during data collection at peak hours of the day, which is indicative of dangerous levels of air pollution.
 
“Even on a holiday like Shivaratri, when there was hardly any traffic on the roads, there was not even a single point in the 30km route where air quality fell within the safe or moderate level," said Sudhir. "In fact, we realised that besides vehicular pollution, which is the main contributor, other pollutants and their sources such as road dust and waste burning are also responsible. For instance, readings shot to 700 micrograms on Avenue Road, which was due to waste burning.”

 
 
Data trust issues?
 
Sudhir's findings shared on Feb. 19 were contested the following morning when an article citing the study quoted a KSPCB official who cast doubt on the readings.  
 
According to The Hindu, the unnamed official was quoted as saying, “Different equipment cost between ₹40,000 and ₹28 lakh. The lower the cost, the worse the calibration...the Central Pollution Control Board specifies 24-hour averages and nearly 12 parameters to be followed. Data should be taken at ambient level (three metres above ground) as closer to the street level, even a passing truck can lead to spikes in pollution.”
 
The question of the data’s reliability rose again a day later at a conference where many air pollution experts were invited by Co Media Lab and Climate Trends, which had done the study.

At the event, B Nagappa, a senior scientific officer with KSPCB, emphasised that data certification and validation is necessary.
 
“ As per the methodology of monitoring, the method of collection; equipment selection etc. has been well defined by Indian standards set by CPCB," he said. "If the equipment is not calibrated and not validated, then it’s bad data. KSPCB is ready to consider the data if people who are conducting independent studies can get it validated and certified from certifying agencies.”  
 
Another expert, Dr SM Shiva Nagendra from the Department of Civil Engineering at IIT Madras, said that low-cost monitors should not be used for assessment and instead should just be used to collect information for better understanding.
 
On the other hand, according to Ronak Sutaria, founder of UrbanSciences, which develops scientifically-validated air quality monitoring networks in India, there is no issue in data accuracy as long as they are measured against reference grade devices and calibrated accordingly. Such an exercise, he said, had to be repeated a few times a year for accurate results.

KSPCB also issued a rejoinder and dubbed the study’s findings “incorrect” on Feb. 23.
 
What do other studies say?
 
Academic findings on the subject of PE and outdoor air pollution say that while ambient PM concentrations are an important contributor to exposure, they often do not correlate with, or are lower than the actual levels of air pollutant exposure for individuals.
 
In fact, studies have concluded that the use of fixed outdoor monitoring stations to estimate PE can lead to exposure misclassification, and therefore, the thrust is now on direct characterisation and quantification of PE to various air pollutants.
 
Commuting is considered a high-exposure activity, and other studies have shown that traffic microenvironment exposures make up a considerable fraction of daily exposure.

Bengaluru in this sense, poses more of a risk, as several reports have said that the city traffic is the slowest in the country and commuters in the city on an average spend as much as 7% of their lives on the road. According to KSPCB data, there has been a growth of 257% in vehicular population over a decade and according to another KSPCB source apportionment study, vehicular emission, in terms of total emission load, continues to be the dominant source (42%) for PM pollution in the city.   
 
A review of several studies (that also cites Bengaluru data) on the subject has concluded that two-wheelers and pedestrians are at maximum risk and those travelling in air-conditioned cars are least exposed to these risks.
 
What do doctors have to say?
 
While clear cause and effect relationships between air pollution and mortality or morbidity are still under investigation, the weight of scientific evidence has swung the pendulum in favour of linkages between them.
 
To analyse their data, the study also contacted doctors for observations.
 
“There is a high incidence of heart attacks among the auto and cab drivers in the city as they spend long hours in slow moving traffic,” said Dr. Rahul Patil, cardiologist at Jayadeva Hospital.
 
“Particulate pollution gets absorbed into the bloodstream within a few minutes and is responsible for blocking the arteries. Bengalureans should become more aware of the rising pollution crisis and not walk and cycle on or near busy roads as the benefits might not outweigh the risks,” he said.
 
Patil's comments are consistent with the opinion of other doctors in different city hospitals that DH had contacted for comments earlier.