As a research scientist, I have extensively studied atmospheric pollution, from vehicle emissions to particulates emitted by factories and power generation facilities. But as the founder of Hamza Mbareche Consulting, most of my work focuses on detecting airborne risks indoors.
This is where a great deal of danger to health and safety is located — and it is also a category that is frequently overlooked by observers seeking to quantify toxicity in the air.
And yet, we spend most of our time indoors. This is especially true in Canada during the winter season, of course. Writing in Nature, the international journal publishing peer-reviewed research in science and technology, a team of air quality researchers noted that indoor air pollution likely causes as many deaths worldwide as outdoor pollution: “3.2 million in 2020, according to the World Health Organization, compared with around 3.5 million linked to polluted outdoor air.”
The article, published in February of this year, was authored by Alastair C. Lewis, a professor of atmospheric chemistry at the National Centre for Atmospheric Science and University of York in the U.K., Deborah Jenkins, a public health specialist, and Christopher J. M. Whitty, the chief medical officer for England.
They noted that in most countries indoor air quality is not regulated. There are some notable exceptions — France requires regular air monitoring in schools — but the risks associated with indoor air pollution are typically not top of mind for policymakers, administrators or even architects and builders.
“Indoor air contains a more diverse range of pollutants than does outdoor air,” explain the authors. “Some are common to both. For example, wood and coal fires and cooking stoves emit large amounts of particulate matter. Natural-gas boilers give off nitrogen oxides. Other pollutants are much more common indoors. Carbon monoxide is released from incomplete combustion, formaldehyde from building materials and glues, and radon from natural radioactivity in bedrock beneath buildings. All of these can accumulate and reach higher concentrations inside than outside.”
I would add to this list furniture whose materials can release formaldehyde, along with plastics and other household products that can produce dangerous organic compounds. Carpets are a source of bacteria and fungi, which can be aerosolized into the air by routine activities such as walking. Mold growing on surfaces and within walls can generate airborne fungus particles, and dust facilitates the transmission of dust mites.
There are many types of hazardous particulates, including bacteria, viruses, fungi and man-made substances such as asbestos that are linked to cancer. Many of these particles can linger in the air, and often become widely dispersed.
The research team notes that as countries have made progress in reducing carbon emissions by improving energy efficiency, indoor air quality has sometimes been collateral damage. One example of this are double-paned windows that keep heat in during winter and cooler air in during summer but also inhibit ventilation, allowing higher concentrations of contaminants in the air.
Another interesting aspect of the problem is the fact that indoor air quality can vary widely among homes in the same neighborhood, and even within a particular dwelling: “Construction styles and materials, climate and energy sources, as well as behaviours and cultural practices, all affect indoor air. In identical houses on the same street, concentrations of volatile organic compounds can differ by factors of around 1,000 owing to differences in occupant behaviour alone.”
Solutions include greater regulatory oversight, changes in building design and construction practices, and use of advanced indoor air filters.
Sometimes, note the authors, the best solution is the simplest one: “Air filters (sometimes called purifiers) are good at lowering levels of particulates indoors, including PM2.5, bioaerosols and viruses, but are less effective for gaseous pollutants. Air filtration is expensive and energy-consuming; in some places, it might be more effective to open a window.”
Perspectives on Air Pollution Risks, From the Inside Out
