Over the last week, air pollution in Chennai has made headlines with the Central Pollution Control Board (CPCB) labelling the city's air quality across various locations, 'poor' to 'very poor'. However, despite the alarming figures presented by the board and the smog enveloping the city in the mornings, the state government after a high-level meeting on Monday said that there is no reason to worry.
The Revenue Department has blamed the deteriorating air quality in the city on the low-pressure system caused by Cyclone Bulbul and on possibly faulty meters in the CPCB monitoring stations.
"Due to the Bulbul cyclone, the cloud cover has descended. So in such a situation, the sun's rays do not come through. And there will be lesser sea breeze, therefore increasing pollution. This is in addition to pollution caused by vehicles, construction sites and burning of garbage," said Revenue Minister RB Udhayakumar.
Commissioner of Revenue Administration J Radhakrishnan further added that in monitoring stations controlled by the state pollution control board, the Air Quality Index (AQI) reading were at least a 100 points lower
AQI considers eight pollutants – particulate matter 10 (PM10), particulate matter 2.5 (PM 2.5), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), trioxygen (O3), ammonia (NH3), and lead (Pb) while calculating the quality of air.
As per the National AQI, 0-50 stands for good air quality, 51-100 for satisfactory, 101-200 for moderate, 201-300 for poor, 301-400 for very poor and 401 - 500 for severe. Between November 4 and November 8, Chennai recorded an average AQI of 247.5 in a residential area such as Velachery and 305.75 in Manali, an industrial area.
"In the manually monitored state systems, the AQI is atleast 100 points lower in some stations," said Radhakrishnan. "We have 28 stations across the state. And the CPCB and mobile units show different figures, so this could be a problem with the Centre's systems," he added.
Dr Shiva Nagendra, a professor from IIT Madras' civil engineering department and expert on the panel argued that manual station have more reliable metre readings.
"The calibration of the CPCB systems may have to be checked because it is continuously monitoring," he said. "Plus AQI itself provides very localised figures and in areas which you can expect to have high concentrate of pollutants like dumpyards and industrial areas," he added.
Revenue officials informed the media that a meeting was scheduled with the CPCB to discuss the vast difference in readings.
Pooja Kumar of the Coastal Resource Centre admits that devices used for constant monitoring could face glitches but that a real picture will be gleaned after the calibration of the devices.
"Such a large difference in values is definitely worrisome," she admits. "However, what is more important here is to contain point and non-point sources of pollution,” Pooja says, referring to industrial and vehicular emissions. “Yes, the low pressure created by the cyclone could be interrupting dispersal of this pollution but it is not the cause for it. What if there is an extended period of low pressure? We need to carry out measure to cut out emissions," she adds.
Radhakrishnan did concede that measures must be taken to reduce pollution and stated that instructions had already been given to various departments for the same.
"We have already told the transport department to conduct checks and monitor vehicle emission. In addition to this, no garbage burning will be allowed," he said.