Most of us tend to think of air pollution in terms of what is outside the house or building we are currently in: exhaust from motor vehicles on the streets, smoke and industrial fumes perhaps, but is the air we are breathing inside, any better? Is it posing a risk to our health? And can building and designing urban infrastructure better, help mitigate indoor air pollution hazards?
In India, while conversations around outdoor air pollution have gained ground, the same focus has not yet been given to indoor air quality in buildings, despite the fact that most people in urban areas spend 70 to 90% of their time indoors, says Kalpana Balakrishnan Dean (Research), Sri Ramachandra Institute of Higher Education and Research, Chennai.
Understanding indoor air pollution
While the major proportion of indoor or household air pollution in India still comes from the use of solid fuels for cooking, primarily in rural areas, in urban areas, where the switch to cleaner fuels such as gas has mostly been made, there are several other sources of indoor air pollution.
Indoor Air Quality (IAQ), as per the U.S. Environmental Protection Agency (EPA), refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns, it says.
“Indoor air pollution is a very broad term as it comprises both indoor sources of pollution as well as pollution from outdoors that has infiltrated indoors. In India, it is very difficult to distinguish between the sources, because unlike other countries, where homes and buildings might be more insulated from the outdoors, this is not the case with most places in our country, making air pollution heterogeneous. Our biggest concern here is the penetration of outdoor air indoors,” says Dr. Balakrishnan.
Outdoor (ambient) air pollution is grouped as class 1 carcinogen, meaning it is cancer causing, apart from contributing to a whole host of other diseases including respiratory ailments, cardiovascular disease and diabetes.
This apart, explains Dr. Balakrishnan, indoor air pollution sources also come from the activities that take place in a building as well as the building (and materials used) itself. “For instance, indoor smoking, cooking/deep frying, chemical cleaners used, the use of mosquito coils or incense sticks could all impact the quality of air indoors,” she says. And then, the building itself – the furnishings in it, vapours from the paint or plastering on the walls, as well as biological contaminants such as mould, can also contribute to indoor air pollution and impact the health of people using the building, she explains.
Some indoor air pollutants
Allergens are substances that can trigger the immune system, causing an allergic reaction; they can circulate in air and remain on carpets and furniture for months.
Asbestos is a fibrous material formerly used for making incombustible or fireproof building materials. Disturbing asbestos minerals or asbestos-containing materials can release fibers, often too small to see, into the air. Asbestos is known to be a human carcinogen.
Carbon monoxide is an odorless and toxic gas. It is found in fumes produced any time you burn fuel in cars or trucks, small engines, stoves, lanterns, grills, fireplaces, gas ranges, or furnaces. Proper venting or exhaust systems prevent build up in the air.
Formaldehyde is a strong-smelling chemical found in some pressed wood furniture, wood particle cabinets, flooring, carpets, and fabrics. It can also be a component of some glues, adhesives, paints, and coating products. Formaldehyde is known to be a human carcinogen.
Lead is a naturally occurring metal that has been used in a wide variety of products including gasoline, paint, plumbing pipes, ceramics, solders, batteries, and even cosmetics.
Mould is a microorganism and type of fungus that thrives in damp places; different moulds are found everywhere, indoors and outside.
Pesticides are substances used to kill, repel, or control certain forms of plants or bugs that are considered to be pests.
Radon is a colorless, odorless, naturally occurring gas that comes from the decay of radioactive elements in soils. It can enter indoor spaces through cracks or gaps in buildings. Most exposures occur inside homes, schools, and workplaces.
Smoke, a byproduct of combustion processes, such as from cigarettes, cookstoves, and wildfires, contains toxic chemicals like formaldehyde and lead.
Source: National Institute of Environmental Health Sciences, U.S.
What can indoor air pollution do to your health?
The EPA states that health effects from indoor air pollution can be experienced soon after exposure, or possibly, years later. Some of the immediate effects it lists are irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable. However it notes that some effects may be similar to those from colds or other viral diseases, making it important to pay attention to the time and place symptoms occur.
Health issues that may show up either years after exposure has occurred or only after long or repeated periods of exposure may include some respiratory diseases, heart disease and cancer, it says.
A build-up of carbon-di-oxide within an indoor space due to a large number of people using the same space, combined with poor ventilation, is also well known to cause symptoms of sickness.
Generally, it is challenging to precisely point out to what extent poor IAQ can affect health, as information regarding the association between the two is inadequate, states a 2021 paper, ‘An Investigative Study on Perceived Indoor Air Quality During COVID-19 Lockdown in India’ by T.K. Bedi et al. However, it adds, this should be considered a public health issue.
Can better building design help with indoor air pollution?
Prioritising indoor air quality in design is crucial, says Mahesh Ramanujam, president & CEO,Global Network for Zero, an independent green certification body helping businesses, buildings, and cities achieve net-zero emissions. One major reason for indoor air pollution, he points out is that there is a lack of good ventilation – most buildings and houses tend to shut their doors and windows to keep the outside out, meaning there is poor air flow, resulting in the circulation of air over and over, giving a chance to pathogens to spread.
In settings where it is possible, he says, opening doors and windows and bringing in sunlight as well as the use of plants indoors can help. Sunlight is known to have beneficial effects on health and aid in recovery. But where this is not possible, say in healthcare facilities where sterile settings are important, designing and building to minimise indoor air pollution can go a long way.
When it comes to the building itself, he says, for several years now, there has been a focus on decreasing the use of volatile organic components like formaldehyde as a strategy to address health and well-being.
An intentional design process that incorporates, for instance, skylights, bringing daylight into pathways and hallways and designing spaces that allow for the movement of people, can help. This can be combined with the use of air purifier units, high quality HEPA filters to keep out particulate matters and using toxin-free cleaners and greenery where possible, to help with improved air and better health.
‘Do it while planning’
Studies suggest that indoor concentrations of air pollutants are increasing, driven by factors such as the types of chemicals in home products, inadequate ventilation, hotter temperatures, and higher humidity, says the U.S.’s National Institute of Environmental Health Sciences. This may be of especial concern in India, where a spike in heat, combined with humidity in coastal cities is already beginning to show impacts on health.
Healthy design elements are easy to incorporate while building a new structure but can also be retrofitted in existing old buildings though this may be more challenging, says Sumita Vasudevan, an associate at APRObuild, an architecture and interior design firm based in Chennai. “Earlier, anything that was green was more expensive, but costs have come down, making the difference only marginal; green elements are now part of the design in most buildings. Post Covid-19, there has been a focus on filtered air, and this is incorporated now into buildings, especially places such as hospitals, through design,” she points out.
Buildings that are going to have most rooms air-conditioned must focus on: easy-to-maintain surfaces, separation of zones and ease of movement so that there are not too many people using the same room together, natural lighting where possible, proper waste disposal, and in settings where necessary, good air filters, said Ms. Vasudevan.
Where a sterile setting is not required and air pollution outdoors is not much of a concern, a back to basic approach may be beneficial: open your windows for ventilation and surround yourself with greenery.
Published – April 07, 2025 05:54 pm IST