Toxic air: Indoors as bad as outdoors

NEW DELHI: Millions of Delhi residents cling to a comforting belief: that shutting the door is enough to keep the city's poisonous air at bay.

- Jasjeev Gandhiok, Ridhima Gupta and Gargi Shukla

But a week-long field experiment by Hindustan Times has punctured that illusion. It showed that the boundary between outdoor and indoor air is porous, fragile, and often meaningless. It found that polluted outdoor air is seeping indoors with limited attenuation, entering through ventilation systems, open doors and windows, or simply through the everyday leakage of buildings not designed to withstand such extreme environmental stress.

More troublingly, it shows no evidence that institutions like hospitals and schools where those most vulnerable spend their days act as protective buffers.

To understand just how severe this exposure is, Hindustan Times tracked pollution levels not only outdoors but inside spaces where vulnerable populations spend much of their day. Over a week from January 14 to 20, three reporters logged PM2.5 levels at the same time each day between 10am and 11.30am - at a private school, a major hospital and a residential home in different parts of the city. At all three locations, pollution levels exceeded national safety limits by as much as seven to eight times nearly throughout the week.

The data showed that unless one is inside a sealed, sanitised room with a high-efficiency air purifier running continuously, there is no real escape during severe pollution episodes. Schools, hospitals and waiting areas-spaces meant to protect

children, newborns and the sick -are, in many cases, breathing almost the toxic haze as those beyond their walls.

To establish a control environment, an air purifier was kept running in a room inside a Vikaspuri house. There, PM2.5 levels dropped as low as 18 micrograms per cubic metre (ug/ m³)-comfortably under India's national safe limit of 60µg/m³ and the World Health Organization's guideline of 15 μg/m³.