Items of everyday use – room fresheners, deodorants, mosquito coil, incense sticks, wall-to-wall carpets and office printers and photocopy machines – could be pushing up indoor pollution levels at homes and offices, which could be as bad as the polluted air outside or even worse, at least two recent studies in Delhi have shown.

Both studies found the concentration of volatile organic compounds and PM2.5 — ultrafine particles that reach up to the lungs — are higher than the permissible limits even inside closed rooms in residences, corporate and government offices and multiplexes.

The concentration of bio-aerosols, which comprise disease-causing agents such as bacteria and virus among others, have been found to be at least 20 times higher in corporate offices and four times higher in multiplexes.

While one study was conducted by a team of researchers from the CSIR-Central Road Research Institute (CSIR-CRRI) in their own offices, another study was done by the Indian Pollution Control Association (IPCA), a Delhi-based research organisation in 13 buildings across Delhi, including corporate offices, a multiplex, government buildings and residences.

The CRRI study was published in Current Science journal on November 10 with data of 2014 summer. The IPCA study was conducted between January and September 2018.

“The concentrations of PM1, PM2.5 and volatile organic compounds (VOCs) were found to be higher inside than outside. While concentrations of PM1 and PM2.5 were nearly double in indoor air than outdoor, the concentration of VOCs was even higher. VOCs accumulate more when air conditioners are used because the ventilation is less,” said Manisha Gaur, one of the authors of the study and a research scholar at CRRI.

Experts said that while any form of combustion such as smoking, or burning an incense stick or mosquito coil, could push up levels of finer particulate matters, the concentration of VOCs shoot up because of use of room fresheners, deodorants, paints, polishing and cleaning agents.

“The concentration of VOCs was particularly found to be nearly two times higher than the safe limits prescribed by the World Health Organisation inside corporate offices and hospitals. It was also very high in the indoor air inside multiplexes. In residences, the level of PM2.5 was found to be 137µg/m3, which is more than two times above the safe limits of 60µg/m3,” said Radhan Goyal, deputy director of IPCA.

The IPCA study found that another pollutant, known as bio-aerosols, was much higher than the permissible limits. It was at least 20 times higher in corporate offices and four times higher in multiplexes. Bio-aerosols comprise airborne bacteria, fungi, viruses and their by-products, endotoxins and mycotoxins.

“Indoor air pollution is particularly higher because of improper ventilation. In more than 90% of the air-conditioned buildings, it is the stale indoor air which is circulated instead of allowing fresh outside air to come in, as it requires consumption of more energy. Outside pollution also gushes in through leakages in door and windows because of difference in air pressure. The pollution tends to be higher towards the corners of the room. Secondly wall-to-wall carpets are known to be sinks of bio-aerosols,” said Mukesh Khare, Mukesh Khare, a professor of environmental engineering at IIT-Delhi

Experts said that these studies are in tune with several other studies carried out across the world and also by the Central Pollution Control Board.

“Indoor pollution often tends to be higher because of poor ventilation, cooler temperature and indoor activities, which include smoking and burning of coils and incense sticks. VOCs, many of which are carcinogenic, tend to move towards cooler temperatures. The wind inside a room is also stagnant compared to outdoor. Hence pollution tends to shoot up,” said T K Joshi, environmental health advisor to the union environment and forest ministry.

He said a previous study done by the CPCB a few years ago had also found that indoor pollution in flats (residences) was higher than outdoor pollution.

“It is a myth that indoor air is less polluted that outdoor air and that you are safe whence you enter home or office. In fact indoor air in poorly ventilated rooms gets more polluted, as the air gets trapped inside and continue to circulate,” said Khare.

First Published: Nov 20, 2018 13:09 IST