The seemingly crisp, fresh air inhaled inside the sanitised and cool environs of metro premises or air-conditioned car may actually be teeming with respirable pollutants.
Pollutants may be entering underground metro premises not only through air conditioning ducts but also clinging on to the clothes and shoes of passengers.
According to experts, not only metro stations, air-conditioned cars and rooms sprayed with freshners are equally, and in cases more, polluted as outdoors.
To its credit, the Delhi Metro authorities have actually helped bringing this fact to light by cooperating with a team of IIT-Delhi which collected data in this regard, which is now being analysed.
Professor Mukesh Khare of IIT-Delhi, who led the study, 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, at places over 600 micrograms per cubic metre. Even level of PM 10 remains high," Khare said.
"Not only the air ducts suck polluted air, but pollutants get carried inside through clothes people wear as well, like on the rough textures of shirts, through shoes," Khare said.
PM 2.5 and PM 10 are respirable pollutants, that can enter the bloodstream and cause harm to the respiratory system on prolonged exposure. Their safe limits are 60 and 100 micrograms per cubic metre in Indian standards.
When contacted, 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.
TK Joshi, Director, Centre for Occupational and Environmental Health, said 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 of the fact that it contains methyl alcohol which is extremely toxic. Practically every air freshner brand uses that. They should be rather called air polluters. People have actually turned blind over prolonged exposure to it," Joshi said.
