The transport department has asked all government departments to dump vehicles that are aged 15 years or older.

Calcutta police have more than 180 such vehicles. The transport department has more than 100 and the health department more than 40 such vehicles.

Studies have shown that vehicular emission is one of the biggest sources of air pollution in Calcutta.

In 2008, Calcutta High Court had banned all vehicles aged 15 years or older in the Calcutta Metropolitan Area (CMA) to bring down vehicular pollution.

The CMA covers the city and municipal areas in the adjoining districts of Howrah, Hooghly, North and South 24-Parganas, and a part of Nadia.

In the absence of a concerted attempt to enforce the order, thousands of government and private vehicles more than 15 years old are a common sight in the city.

Transport secretary N.S. Nigam, in a letter, has asked all other departmental secretaries to phase out all such vehicles by December 31.

The letter was sent to more than 50 departments last week, including the city police, Calcutta Municipal Corporation and Calcutta Metropolitan Development Authority.

Lalbazar bosses have informed the transport department that 82 such vehicles, most of which had been hired from various agencies, have been dumped.

A little over 100 such vehicles are still in use, they have said.

The phasing out of vehicles more than 15 years old had come up for discussion at a recent meeting convened by chief secretary Rajiva Sinhto take stock of the steps being taken to combat air pollution.

The National Green Tribunal had fined the government Rs 10 crore for failing to check air pollution. The tribunal had directed the chief secretary to appear before it on November 4.

Vehicles that are 15 years old or older affect the air quality index because exhaust fumes have a higher presence of hydrocarbons.

The pollution level could worsen during winter, when the wind velocity is low and particles remain suspended in the atmosphere immediately above the earth’s surface for a long time and do not get dissipated.

“This letter is aimed at impressing the National Green Tribunal. We have reasons to believe that close to a lakh of vehicles aged 15 years or older are plying in and around Calcutta,” Subhas Dutta, environment activist, said.

Dutta has petitioned before the tribunal against such vehicles. “The vehicle count here may not be as high as in Delhi but the presence of a large number of vehicles more than 15 years old and poor traffic management add to the pollution problem.”

A CMC official said the civic body used several such lorries to carry garbage to the dumping ground in Dhapa. “These lorries will be phased out within a month-and-a-half and new vehicles brought in.”

This is not the first time that the transport department has flagged its concern on vehicles more than 15 years old.

In January, the department had issued a notice banning the entry of such vehicles in Calcutta and Howrah.