Beyond AQI, why poor indoor air quality is also a matter of health concern

In their study, they examined the correlation between construction and demolition practices and the deterioration of IAQ, identifying common pollutants such as PM2.5, PM10, carbon monoxide, NOx (nitrogen oxide), and volatile organic compounds (VOCs or gases that are emitted from many household products and processes, including paints, cleaners, and fuels). Benzene emerged as the most dangerous, followed by carbon monoxide, VOCs and radon. The study was published in the Royal Society of Chemistry journal.

“The biggest indoor pollution is from construction dust from sites near your home, or even renovation and refurbishing of your own home. The total volume of construction and demolition dust has gone up from 150 million tonnes in 2016 to 300 million tonnes today. By 2030, this is expected to go up to 430 million tonnes,” says Ganesh. The study calls for including IAQ standards in building codes, smart cities and workplace regulations.

How is the IAQ scale different from air purifiers?

Ganesh: High-end model air purifiers measure only particulate matter and humidity, which is not comprehensive enough for calculating indoor air quality. The USP of the proposed sensor system is to measure all the critical pollutants that are required to estimate the indoor air quality and present their values.

Is there an IAQ monitor in use in the West?

Ganesh: Yes, the US, UK and EU have their standard scales. However, we don’t have anything customised for our geographical lay of the land, climate, population, the nature of housing and economic resources.

What are the health impacts?

Choudhury: Poor IAQ is linked to sick building syndrome, which triggers headaches, fatigue and irritation. Given that most modern constructions lack cross ventilation, poor IAQ can cause asthma, bronchial allergies, COPD (chronic obstructive pulmonary disorder), reduced immunity, cardiovascular disease and cancer. Women and infants are the most vulnerable due to longer indoor exposure and cooking-related emissions.

What is the new scale based on?

Choudhury: We did a pan-Indian survey of indoor environment and indoor pollutant concentration based on age groups, income category and geography. We refined that data and fed it into a learning model, and decided to have a scale based on four weighted parameters. We graded our scale, assigning 59.5 per cent to pollution concentration, 25.9 per cent to exposure time, 9.8 per cent to ventilation efficiency and 4.4 per cent to enclosure size. This weighting reflects India’s dense urban living, varied housing sizes and ventilation challenges.

A score has been calculated based on these inputs, ranging from 22 to 100, 22 being the most severe and 100 being the best quality.

What are the key findings from your study?

Our study found that fine particulate matter, such as PM2.5 and PM10, can rise well above safe exposure limits during routine activities like cooking and cleaning. Poor ventilation causes these pollutants to accumulate, making the indoor environment even more harmful. Seasonal fluctuations — especially during winters and festive periods — further worsen indoor air toxicity.

What are the unexpected sources of indoor pollution?

Choudhury: Many don’t know that benzene is generated by aromatic disinfectants. In a closed setting and with low oxygen, incomplete burning of incense sticks produces carbon monoxide. When organic waste is not segregated and is left to decay in bins, it releases methane and foul-smelling gases indoors. Methane is a powerful climate-warming gas — around 80 times stronger than carbon dioxide over a 20-year period — and it contributes to ozone layer damage and harmful ground-level ozone that affects breathing. It can also pose fire risks if accumulated in confined spaces. Even a small dustbin may act like a mini-landfill if waste is not properly separated, so a simple habit of keeping wet and dry waste separate can protect both household air and the environment.

What can households do today to reduce indoor pollution?

Households can take simple yet impactful steps such as improving ventilation by opening windows during low-pollution hours, using exhaust fans during cooking, reducing incense burning, and segregating organic waste. Regular dusting, indoor greenery, and minimising synthetic air fresheners and harsh chemicals can further improve air quality. Small lifestyle changes can create healthier homes.