IIT-K’s air quality sensors highlight the need for hyper-local air quality monitoring

The air quality index (AQI) and particulate matter levels flashing on your nearest Central Pollution Control Board (CPCB) monitoring station might not be correctly reflecting the air quality in your neighbourhood, according to an analysis of data recorded by IIT-Kanpur’s hyper-local air quality monitoring sensors in Delhi.

Data from 30 hyper-local air quality sensors installed across Delhi show the role of local factors such as vehicular movement, local fires on the air quality and how it changes every few kilometres.

These sensors were installed from October 21 with an aim of assessing neighbourhood air quality data. Some of these sensors are located near CPCB stations while others are at a distance of 1 to 10 km away.

When entire Delhi was reeling under an air emergency between November 5 and November 11, recordings of PM 2.5 levels (ultrafine particulate matter with diameter less than 2.5 micrometres) in CPCB’s 36 monitoring stations and the hyper-local sensors installed by IIT, were similar.

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However, on November 12 and November 13, when, according to CPCB’s monitoring stations, the pollution levels improved to ‘very poor’ levels (PM 2.5 levels below the 250ug/m3 mark) in places such as Mundka (near Ghevra), Rohini sector-4, Pooth Khurd Village, Narela sector A-8 and Chhawla BSF Camp, the PM 2.5 levels recorded by the hyper local sensors at the same places continued to remain above the 450ug/m3 mark (emergency levels).

Scientists said this was proof of how important it was necessary to have more air quality monitoring at a local level and across the city.

Professor Sachchida Nand Tripathi, head of the department (civil engineering), member of the National Clean Air Programme (NCAP) who is leading this project along with professor Abhay Karandika, director, IIT-Kanpur, said while data from primary air quality monitoring stations were important, it was those from these hyper-local sensors that actually affected the lives of people.

“If I want to go out for a run or I have a senior citizen or a child at home and want to know the air quality levels in my area, I need to know the pollution level in my location. The nearest CPCB or DPCC (Delhi Pollution Control Committee) monitoring station could be six, seven or even 10 kilometres away. So, what is actually affecting me is not shown in the readings of monitoring stations,” explained Tripathi.

For instance, in an area like Najafgarh, which has sources such as stubble fires, open burning and road dust, there is only one monitoring station covering a 30 km area. Similarly, despite the heavy traffic volume in Dhaula Kuan, the nearest CPCB monitoring station is located at RK Puram, around eight kilometres away.

On November 15, a day after Diwali, the readings of these IIT-Kanpur neighbouring sensors showed that in 28 out of the 30 localities, the PM 2.5 levels were above 480ug/m3. It shows that in residential areas such as Rohini sector-4, Noida sector-134, Noida sector-78 and RK Puram, the levels were higher compared to industrial areas and transport hubs, which clearly showed the impact of cracker bursting.

Between October 21 and November 3, when the city was receiving relatively cleaner air, the PM 2.5 reading at the Sahibabad sensor was above 200ug/m3 for 13 out of the 14 days. In Jahangirpuri, Anand Vihar and Bawana, the levels were above the 200ug/m3 mark for 12 out of 14 days.

Explaining the data reading, Tripathi said when micro-climates in a locality were at play, there was a difference in the recordings of these sensors compared to the 36 CPCB monitoring stations.

It was also noted that in the absence of any major change in micro-climate (local factors), the readings in these sensors and the CPCB stations were similar.

“This shows the accuracy of these low-cost neighbourhood sensors. Delhi-NCR is a vast region and improving air quality monitoring is the only way to solve the problem of pollution here. At present, we have around 36 monitoring stations, but for a city like Delhi, you need at least 200-300 air quality sensors to correctly assess the pollution levels. In cities such as Beijing and London, there are hundreds of air quality monitoring systems, which ensures the accuracy of information,” he said.

A senior CPCB official, who did not wish to be identified, said they are working with states concerned in Delhi and NCR to increase monitoring. “From around 16-17 stations, we have increased our monitoring to 38 and now we will be increasing the network more. Surely, with more data, the analysis of pollution will be better,” the official said.

Anumita Roychowdhury, executive director (research and advocacy), Centre for Science and Environment, also stressed on the importance of neighbourhood monitoring for a more accurate analysis of pollution levels.

“Importance of accurate data cannot be underestimated because for any action to control pollution levels will have to come after analysing this. In many states in northern India, pollution levels are high but because there are only one or two AQI monitoring stations, we do not get a clear picture of the extent of the problem,” she said.

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The development of these sensors, which have been designed to measure particulate matter of the size 10 micrometres (PM 10) and 2.5 micrometres (PM 2.5), is part of a collaborative project between IIT-Kanpur, Mumbai-based Respirer Living Sciences and Ericson (India), which for the first time in India has used the Narrow Bandwidth-Internet of Things (NB-IoT) technology.

This new technology primarily helps saves energy and can sense and transmit more effectively than the air quality monitoring sensors already installed in Delhi-NCR, IIT-Kanpur scientists explained.

Data generated from these sensors will be shared on a common platform to help community groups in understanding air quality situation in their areas and will government agencies to mitigate policies.