The seemingly crisp, fresh air inside the sanitised environs of the Metro premises or an air-conditioned car may actually be teeming with respirable pollutants.

Pollutants may be entering underground metro premises not only through AC ducts but also clinging on to the clothes and shoes of passengers.

Experts say that besides metro stations, air-conditioned cars and rooms sprayed with freshners are as polluted — if not more — as the outdoors.

The Delhi Metro authorities have helped bring this fact to light by cooperating with a team from IIT-Delhi, which collected data in this regard. Professor MukeshKhare, who led the team, told PTI that the complete report will be out in three to four months.

“Premises of metro stations in Delhi have high concentration of PM 2.5 going as high as 600 micrograms per cubic metre. The levels of PM 10 are also high,” Mr. Khare said.

“Not only do the air ducts suck polluted air, the pollutants get carried inside through clothes and shoes of the passengers,” he added.

PM 2.5 and PM 10 are respirable pollutants that can enter the bloodstream and cause harm to the respiratory system on prolonged exposure. As per Indian standards. their safe limits are 60 and 100 micrograms per cubic metre respectively.

A senior Delhi Metro official said that the air-conditioning system of the network has in-built provisions to flush out air, but at times respirable pollutants get air-borne and there is a build up.

“That is why we frequently mop the floors of our stations, specially the entry and exit of underground stations. It also depends on the level of outdoor pollution,” the official said.

‘Toxic’ room freshners

Director of the Centre for Occupational and Environmental Health, T. K. Joshi, said that while the focus has largely been on outdoor pollution, the same phenomenon plays out inside our dwellings as well. “People often spray room freshners, oblivious to the fact that it contains methyl alcohol, which is extremely toxic. Practically every air freshner brand uses it. They should be rather called air polluters. People have actually turned blind over prolonged exposure to it,” Mr. Joshi said. — PTI