Other States

One air quality sensor for an entire city?

On November 8, two days after Diwali, the particulate matter (PM2.5) reading in Agra had shot up to 375, or ‘very poor’ in the Air Quality Index (AQI). This was as per a measurement by the city’s lone automatic monitoring station. However, on the same day, the PM2.5 concentration, according to a manually-operated station at the Taj Mahal, was 273 or ‘poor’ air quality.

While Agra doesn't have a Graded Response Action Plan (GRAP) like Delhi does, a 102-point disparity is highly problematic. It could mean the difference between, say, opting for just a ban on construction activity or banning private transport altogether.

Given the way India’s air quality monitoring infrastructure is set up, most cities have only a single air monitoring device that provides continuous real-time updates on particulate matter, sulphur dioxide, and NO2 concentrations. This is the Continuous Ambient Air Quality Monitoring System (CAAQMS), also known as an automatic monitoring station.

At any given moment, it is this automatic unit that represents (its figures are instantly available on the Central Pollution Control Board [CPCB] website) the city air quality. Agra, incidentally, figures in the World Health Organisation (WHO) database of the world’s most polluted cities.

Agra has a total of eight air-quality monitoring stations. Of these, seven are manually operated and located in different parts of the city. Their readings are taken twice a week. With the manual monitoring stations, daily readings are not made available. Only readings averaged over a month are released, that too with time lag of a couple of months. So if there is, say, a sharp dip in air quality in a span of 24-48 hours, as happened this year in Delhi around Diwali, then these stations, given the way they are operated at present, cannot provide real time actionable data. And this, according to officials, becomes a problem when emergency measures need to be taken.

One air quality sensor for an entire city?

The automatic monitoring station in Agra is situated in the busy commercial district of Sanjay Place, atop the city’s municipal corporation building. The two-storey building sits a few kilometres away from an intersection of highways and therefore, said an official in the CPCB, the unit picks up high volumes of particulate matter from passing trucks and vehicles. “By no means can a single station capture the varying levels of pollution in entire the city. However, we’ve chosen this location because it somewhat reflects the average,” said the official, who didn’t want to be identified. Agra’s industrial hub Ramgarh has, on average, higher PM readings whereas the Taj Mahal, given its location away from the bustle of the city, tends to have better ambient air.

“We do plan to have a second automatic station soon to get a more representative picture of Agra’s ambient air quality,” he added.

The problem is the cost. A continuous monitoring system costs about ₹1.5 crore, whereas a manual system comes for half of that. The CAAQMS at Agra is jointly funded by the State and the Centre and the maintenance and upkeep is the State’s responsibility. “Ideally, we would all like to have CAAQMS,” said Atulesh Yadav, Regional Officer, Uttar Pradesh Pollution Control Board. “However, we need a proper spread to get a truly representative picture.” The State and Central Pollution Control Boards are independent of each other, with the State units vested with greater responsibilities in terms of both measuring and controlling pollution levels.

In the 17 States and Union Territories where the CPCB has its network of CAAQMS stations, just 9 out of 131 cities have more than one unit, with only Delhi having an out-sized 37 stations.

High cost a deterrent

Not far from Delhi, the industrial town of Bhiwadi in Rajasthan made the headlines earlier this month when it notched up the worst air quality in the country on Diwali eve. Falling as it does in the National Capital Region (NCR), around 20% of its industrial units were forced to remain shut for nine days in November this year.

Bhiwadi has around 1,200 industrial units spanning a range of sectors, including auto parts, ceramics, chemicals, drugs, glass, iron and steel, packaging, and bathroom fittings. Thanks to the thriving industry and the town's proximity to Delhi, the real estate sector has enjoyed a tremendous growth in the region in recent times, causing a rapid rise in its population.

The growth in industry, population and traffic has increased air pollution levels in the town. But its infrastructure to measure them is far from inadequate. The town extends across 8,000 acres but it has only one CAAQMS, located at Ajanta Chowk in RIICO Industrial Area Phase-III, and three manual stations to validate its readings.

Neha Agarwal, the Scientific Officer-cum-Laboratroy Incharge at Rajasthan State Pollution Control Board, Bhiwadi, said that ideally at least three CAAQMS were required for the commercial, industrial and the residential areas respectively, for a better estimate of the town’s air quality.

One more monitoring station is in the pipeline, Ms. Agarwal said, but added that the price and the high cost of maintenance and operation (around ₹14 lakh per annum) remained a deterrent. She added that there were only 10 CAAQMS in entire Rajasthan.

Continuous Internet needed

Another single-unit city is Patiala in Punjab, which ranked 13th in WHO’s list of the world’s most polluted cities, released earlier this year. It has only one automatic air monitoring station to record the air pollution round the clock. Experts and local officials both agree that a single CAAQMS cannot represent an accurate picture of air pollution for the entire city, which is the fourth largest in Punjab.

Patiala’s air quality has been worsening over the years due to the burning of crop residue and municipal solid waste, which adds to the pollution caused by industry and vehicular traffic. The Punjab Pollution Control Board (PPCB) recently installed a CAAQMS at its administrative office premises.

The station is located a good distance from the city's nerve centre, which sees a heavy rush of vehicular traffic. The PPCB, however, points out that as per CPCB guidelines, the CAAQMS should be set up at a site where there is no local air polluting source in the vicinity.

Costs of the CAAQMS apart, the unit, to work efficiently, requires continuous power and connectivity to the Internet.

In several cities, these aren’t always available. Even in Delhi, for instance, not every CAAQMS unit would be generating data at a given point in time.

Increasing the number of automatic monitoring stations is high on the Centre’s agenda. The National Clean Air Programme, an initiative to put in place a process similar to Delhi’s GRAP, envisions setting up 1,000 manual air-quality-monitoring stations (a 45% increase from the present number) and 268 automatic stations (three times the current 84). It also, for the first time, plans to set up pollution-monitoring stations in rural areas.

Our code of editorial values

This article is closed for comments.
Please Email the Editor

Printable version | Aug 2, 2021 12:43:43 PM | https://www.thehindu.com/news/national/other-states/one-air-quality-sensor-for-an-entire-city/article25533668.ece

Next Story