Mention air pollution and most people will immediately think along the lines of haze, exhaust fumes, smog from factories – basically the air outdoors.

But the truth is, the air we breathe indoors – in our homes, offices, schools and other buildings – can be more polluted than outside. Moreover, the exposure to and risk of illness from poor indoor air quality is so much higher, given the disproportionate amount of time we spend indoors.

Numerous studies from the US and Europe show that persons in industrialised nations spend more than 90% of their time indoors. For infants, the elderly, persons with chronic diseases, and most urban residents of any age, the proportion is most likely higher.

In addition, the concentrations of many pollutants indoors exceed those outdoors. Studies by the United States Environmental Protection Agency’s (EPA) Total Exposure Assessment Methodology (TEAM) found levels of about a dozen common organic pollutants to be 2 to 5 times higher inside homes than outside, regardless of whether the homes were located in rural or highly industrial areas.

Indeed, the EPA lists indoor air pollution as among the top five environmental health risks!

Even the cleanest home can cause human health problems because of its structure or from the household products we use and keep in our homes.

Pollutants that can affect air quality in a home or other buildings fall into the following categories:

Particulate matter includes dust, smoke, pollen, animal dander (skin flakes from an animal’s hair or fur), tobacco smoke, particles generated from combustion appliances such as cooking stoves, and particles associated with tiny organisms such as dust mites, molds, bacteria, and viruses.

Gaseous pollutants come from combustion processes. Sources include gas cooking stoves, vehicle exhaust, and tobacco smoke. They also come from building materials, furnishings, and the use of products such as adhesives, paints, varnishes, cleaning products, and pesticides.

It is ironic that the seemingly cleanest homes may actually have the worst indoor air quality. Conventional cleaning products and air fresheners that we use to make our clothes and home smell oh-so-nice contain volatile organic chemicals (VOCs). This fact is commonly overlooked and/or ignored. Synthetic fragrances, whether in solid, spray or oil form, may all emit such chemicals into the air. But you will not find their names on the product labels.

Research by a team from the University of Washington on 25 common fragranced consumer products —laundry products, personal care products, cleaning supplies and air fresheners, many of them top sellers in their categories— found 133 different VOCs emitted from the products, with an average of 17 VOCs per product. Of these 133 VOCs, 24 are classified as toxic or hazardous under US federal laws, and each product emitted at least one of these compounds. More alarmingly, emissions of these compounds were not significantly different between “green” products and the other products. Of all VOCs identified across the products, only 1 was listed on any product label, and only 2 were listed on any material safety data sheet.

Concentrations of many VOCs are consistently higher indoors than outdoors. A study by the EPA covering six communities in various parts of the US found indoor VOC levels up to 10 times higher than those outdoors, even in locations with significant outdoor air pollution sources, such as petrochemical plants.

Other common indoor air pollutants are dust mites and moulds. Every home has dust mites, tiny bugs that feed on human skin flakes; they can be found in mattresses, pillows, carpets, upholstered furniture, bedcovers, clothes, stuffed toys and fabric and fabric-covered items. Moulds are microscopic fungi that live on plant and animal matter. They can be found almost anywhere when moisture is present.

As dust mites and mould love moisture, keeping humidity around 30%-50% helps keep them and other allergens under control. However, this would be a rather challenging feat in Malaysia.

Outdoor air pollution can enter buildings and become a source of indoor air pollution too.

A major source of indoor air contaminant is environmental tobacco smoke (ETS), often referred to as "secondhand smoke". Exposure to ETS is often called "passive smoking." Given the ubiquitous nature of ETS in indoor environments, some unintentional inhalation of ETS by non-smokers is unavoidable – think offices and restaurants that allow smoking. ETS is a dynamic, complex mixture of more than 4,000 chemicals found in both vapour and particle phases, more than 40 of which are known to cause cancer in humans or animals, and many of which are strong irritants.

While improved general ventilation of indoor spaces may decrease the odour of ETS, health risks cannot be eliminated by generally accepted ventilation methods. Research has led to the conclusion that total removal of tobacco smoke – a complex mixture of gaseous and particulate components – through general ventilation is not feasible.

Indeed, it would be erroneous to make assumptions about the quality of indoor air simply based on smell, or lack of it. Some things with odours, like vinegar, are harmless for most people when used properly. In fact, vinegar is an excellent natural multi-purpose cleaner and disinfectant. Meanwhile, gases like radon and carbon monoxide are odourless but can be very harmful. Sometimes, chemicals can cause you to feel sick before you notice any odour. Even products labelled “natural,” “safe,” “odour-free” or “unscented” can contain chemicals that may be problematic for some people, especially if overused or misused.

Given that more than 90% of our time is spent indoors, we should do well to pay more heed to our indoor air quality.

This article is brought to you by Blueair www.blueair.com/my