Clearing the air

Working closely with industry partners, Haghighat and his fellow researchers have two primary tasks: testing indoor materials to determine the source of contaminants, and developing technologies and methods to purify the air.

“One of the big issues here is the buildings themselves and the materials inside of them,” says Haghighat. “Look at your desk, the walls around you — they’re painted. Look at the carpet — it’s synthetic material. So many materials are synthetic, and if they’re brand new, they emit gases. If they’re old, they decompose and can also release gases.”

Other than VOCs, some of the more common contaminants found inside buildings include carbon monoxide brought in by air intakes, dust mites from carpets and fabrics, moulds and bacteria from damp areas and stagnant water, and ozone from photocopiers and electric motors.

Another big issue is what people bring inside with them, adds Haghighat.

Back in 2009, he co-authored a report for Public Works and Government Services Canada that included an in-depth analysis of the air quality in several office buildings.

No occupant had complained about the air inside these buildings, yet the researchers found that it was contaminated with a number of harmful gases. Their concentration levels were 10 times higher than what was found outside, says Haghighat.

The main culprit: personal-care items like deodorants and hair-care products.

Photocatalytic air purification systems — which use energy from light to clean the air — are one tool that more people are using to try to combat some of these contaminants. Haghighat and his colleagues have been looking at these too, with sobering results.

“Surprise, surprise, we find that most of them make the indoor air quality worse than before,” he says.

“For example, we’ve found that when a photocatalytic airpurification system is used to remove methanol alcohol from indoor air, it created formaldehyde, which is more poisonous than the original gas.”

In response, Haghighat and his team are currently working on developing new photocatalytic air-purification systems that don’t create hazardous byproducts.

It’s not easy work, he admits. “But we’ve done some preliminary studies that are reducing them. So, you’re always trying to remain optimistic.” 

Smart materials

One researcher from Haghighat’s lab who provided quite a bit of optimism was Zahra Shayegan, PhD 21.

Now a postdoctoral researcher at the Institut national de la recherche scientifique, Shayegan developed a novel solution to help degrade indoor air contaminants as a Concordia student. She not only won the university’s Doctoral Prize in Engineering and Computer Science for her efforts, but a Governor General’s Academic Gold Medal as well.

Thinking about two of the unique challenges to improving indoor air in a country like Canada helped set Shayegan on her research path.

“One is that as Canada continues to pursue its net-zero energy targets, buildings are becoming more airtight,” she notes. This reduces the ventilation that can move contaminants out of the building.

“The second challenge is that we can’t just open our windows in winter to improve ventilation and dilute the air.”

Part of Shayegan’s innovation came through the use of photocatalysts, which are used in a variety of applications, including eliminating pollutants in water. Photocatalysts work by accelerating specific chemical reactions like oxidation through the use of light.

The process doesn’t always work indoors, however. But, using the unique real-world conditions available in Haghighat’s lab, Shayegan developed photocatalysts that can remove indoor air pollutants in humid conditions and using a building’s own indoor light sources.

Materials like these still have to improve before they can be commercialized, says Shayegan. But she sees a near future where that is a definite possibility.

Right now, for instance, some windows are coated with smart materials that improve energy efficiency. “Why couldn’t that be done for improving indoor air, too?” she asks.

“Imagine this: The outside of the window is coated with a smart material to reduce energy consumption, and the inside of the window is coated with a material for the removal of indoor pollutants. I think it’s going to happen soon. We’re not far from it.”

She is now an associate professor of mechanical engineering at the University of Alberta, and has expanded her indoor focus to include other gaseous contaminants, as well as harmful particles and bioaerosols in the air.

Zhong does most of this work at U of A’s Built Environment Technology Lab, which she founded and still directs.

One bioaerosol that she has looked at quite extensively is SARS-CoV-2, the virus that causes COVID-19. More specifically, she and her co-researchers have studied how the virus moves through ventilation systems and how these systems might be designed or adapted to control the virus.

For the past three years, Zhong has focused on exploring ultraviolet (UV) germicidal technology, which uses light to deactivate the DNA of viruses, as well as bacteria and other pathogens.

“This technology is already implemented in places like hospitals, but it’s not so commonly used in commercial and residential buildings,” says Zhong. “Part of my research work is focused on identifying the critical design elements that could expand its use.”

One of the big benefits of using UV technology like this is that it doesn’t use chemicals to disinfect the air. And because nothing is added, the process is relatively simple, inexpensive and requires minimal maintenance.

But this doesn’t mean that the technology is easy to develop at scale or that it’s easy to expand into commercial and residential markets. It’s critical for researchers working on air quality to partner with industry and other researchers, says Zhong.

“The pandemic showed us that we need lots of different people from lots of different countries working on engineering solutions together,” she adds. “These are not easy problems to solve, and so we need collaboration. That’s the only way we can make sure people beyond academia are aware of these problems and are protected.”

Hyperlocal air pollution

Kos says that the two biggest concerns when it comes to outdoor air pollution right now are ozone (a key product of photochemical smog) and particulates, both of which are primarily produced by emissions from motor vehicles, solid-fuel burning and industry.

Wildfires can also be a significant source of pollutants, as they were across Canada this past summer.

Health Canada estimates the annual health impacts of wildfire smoke at $5 billion to $21 billion.

The silver lining, however, is that air pollution in Canada has been significantly declining since the 1970s.

According to the National Air Pollution Surveillance Program, lead concentrations in the air have decreased by 97 per cent, and sulphur dioxide levels by 96 per cent since 1970. Between 1970 and 2008, particulate matter decreased by more than 50 per cent.

But, as Kos notes, these macro numbers don’t tell the whole story. Certain communities and neighbourhoods can be impacted more than others.

“We’ve seen in past years that some streets might be quite badly affected by air pollution because of things like traffic and weather patterns, whereas just a few blocks away are showing much cleaner air,” he says. “This could make a big difference for someone deciding, for instance, if they want to jog on Sherbrooke Street in downtown Montreal, where there could be a lot of air pollution, versus just a few blocks away.”

These hyperlocal air pollution issues are Kos’s focus right now. To get a better understanding, he and his partners deploy several air-monitoring stations in specific areas of a community.

In the Mohawk Territory of Kahnawake, just south of Montreal, Kos has built and deployed about 20 monitoring stations with community members.

“They have been concerned about air-pollution levels for quite a while, and so our goal is to build this dense network of stations with them and then make that data available to the community so that they can decide what to do about it,” he says. 

The science ‘has to be communicated properly’

“There can be more than 10,000 chemicals in the air you breathe,” says Zhang, an assistant professor in the Department of Chemistry and Biochemistry.

“My work is focusing on detecting and screening for this large number of chemicals in the complex mixture of our air and to determine what chemicals are of concern and what are their sources.” 

Zhang also looks at specific groups of chemical compounds, most of which are used in various commercial products.

One example is the organophosphate flame retardants that are commonly found in furniture. Typically, when regulators assess the harmful effects of chemicals like these, they don’t consider what is produced from chemical transformations in the atmosphere.

That’s a problem, says Zhang.

In a 2023 study published in One Earth, Zhang and his collaborators found that the transformation product of an organophosphorus antioxidant is more stable in the environment and causes higher risk than well-known organophosphate flame retardants.

The researcher adds an important caveat about toxicity.

“Usually, when people hear that breathing in a certain chemical can be toxic, they get really concerned,” he says. “But the toxic effect depends on the exposure — how much of the chemical can get into your body through different environmental pathways. Exposure and toxicity together tell you the final risk of the chemical, and that’s what I’m also trying to study.”

The World Health Organization and Health Canada publish details about the harmful exposure levels of various chemicals in its indoor and outdoor air-quality guidelines, Zhang observes.

As for the prospects of fewer harmful chemicals ending up in the atmosphere, he is cautiously optimistic.

“We’re only going to see improvement if all of the different stakeholders are working together,” he says. “The scientific evidence has to drive this, but it has to be communicated properly with policymakers as well as with industry actors that are producing some of these chemicals.” 

A way forward