The Calcutta Municipal Corporation (CMC) on Monday started using two mist cannons to water roads and prevent the resuspension of dust as a measure to keep the air quality under control.
Officials of the civic body said 20 other vehicles are also being used to water the
Air quality management specialists have said that watering roads can help prevent dust from rising in the air, but it cannot be the most
important strategy in combatting poor air quality. Identifying sources of pollution and stopping them should be central in the fight, they have
Mayor Firhad Hakim told Metro on Monday that 40 locations have been identified where water will be sprinkled on roads.
“Some parts of the city are more dusty than others. Water sprinkling will be done in those places. We will also wash the shrubs and trees along roads,” Hakim said.
CMC officials said some of the roads and locations being watered include the Exide crossing, Rabindra Bharati University crossing on BT Road, Shyambazar five-point crossing and the EM Bypass-Park Circus connector intersection.
“We started watering the roads a few days back. The use of two mist cannons started on Monday,” said an official.
While water sprinklers water the road, mist cannons release water droplets in the air, at some height above the ground. The mist cannons were also used during the Covid pandemic, ostensibly to sanitise public spaces like bus stops and markets.
A CMC official said water sprinklers have nozzles in the front and back and along the sides. Watering helps keep the dust settled on the wet road surface and prevents them from rising as vehicles move.
Abhijeet Chatterjee, an air quality management specialist, said mist cannons would be effective on roads laden with dust and at construction sites where a large volume of dust floats in the air.
“Using mist cannons on all roads will not achieve the desired results,” said Chatterjee, a professor at the Bose Institute. “One needs to keep in mind that mist cannons cannot perform the role of rain, which can wash out all pollutants and improve the air quality.”
Chatterjee, who is also an advisor to the CMC on managing the city’s air quality, said he told the civic body that mist cannons should be used at construction sites.
“Usually, a large volume of dust is generated at construction sites and it floats in the air. Water droplets released by mist cannons can help suppress this dust floating in the air, but the measure will not be effective in all places. The CMC should be careful about choosing the places where the cannons can be used,” he said.
“Watering roads can be one of the measures. To cut down air pollution, sources of pollution has to be identified and corrective measures must be implemented,” Chatterjee said.
Calcutta’s air quality was mostly “poor” and “very poor” earlier this month. Over the past few days, it was “good” and “satisfactory”.
A study published in 2019 showed that the transport sector accounted for more than 20 per cent of PM2.5 — the most deadly of all air pollutants — present in Calcutta’s air. More than half of that was emitted by goods vehicles.
The National Environmental Engineering Research Institute (NEERI) had done the study for the state pollution control board.
Open burning of waste and cooking with solid fuels also contribute to poor air quality.