Via Medium, a look at how urban buildings could be polluting our cities just as much as traffic:

Oh, summertime! Longer days, dining in patios, weekends by the pool, and… wait! A sore throat?! Again? Damnit, I have to work from the office today, and I missed my jacket at home. My knuckles are freezing, but I will start sweating when I go outside for lunch. Do I need two outfits when I come to work in the summer?

Please, tell me I’m not the only one having this inner dialogue all summer. Since we are on the topic, tell me I’m not the only one who stops for a few minutes here and there to consider whether urban buildings are polluting our cities, just like traffic.

We often blame traffic and industrial activities for air pollution in urban areas. It’s easy to do so; after all, this is the most visible and talked-about pollution.

However, it turns out I wasn’t the only one wondering about the pollution caused by urban buildings. A recent study led by Dr. Brandon Boor, an associate professor at Purdue University, sheds some light on this less obvious contributor: modern office buildings. This study aimed to understand how these buildings release volatile organic compounds (VOCs) into the urban atmosphere and whether these emissions could rival those from traffic.

Urban air pollution is a growing concern, affecting human health and contributing to climate change. While traffic and industrial emissions are well-documented sources of pollution, the role of buildings in this process has been less understood. In a way, it is hard to think about the pollution of such seemingly static structures without obvious fume chimneys.

Thus, Dr. Brandon Boor and his team wanted to explore the hypothesis that modern office buildings, with their advanced HVAC (heating, ventilation, and air conditioning) systems, are significant sources of VOCs. VOCs are chemicals that can easily become vapors or gases and are known to contribute to air pollution.

“We traditionally think of filtering the outdoor air entering our buildings. Based on the findings of our study, we now need to consider cleaning the air leaving our offices, homes, and schools to reduce VOC emissions to the outdoor environment,” said Dr. Boor.

So, what did they do?

The research team conducted a comprehensive one-month field measurement campaign to test their hypothesis in a high-performance, LEED (Leadership in Energy and Environmental Design) Gold-certified office building in central Indiana. As a reference, this is the highest level of LEED design, so it should be the most efficient for protecting the environment.

This building was continuously mechanically ventilated, providing a perfect setting for the study.

The team used state-of-the-art air quality instrumentation and an advanced building automation platform to measure the outdoor-indoor air pollutant exchange. They focused on three common urban air pollutants: VOCs, ozone (O3), and fine particulate matter (PM2.5). These pollutants were measured in real-time at various points throughout the HVAC system.

“We investigated the source and sink effects of a mechanically ventilated, realistic, open-plan office and its HVAC system on urban air pollutants,” the study noted. This detailed approach allowed the researchers to capture how air quality changed as it moved through the building. In my opinion, a very well-rounded experimental design-

So, what did they find?

The results were striking. The study found that the air coming out of urban office buildings is more polluted than previously believed. Indoor VOC concentrations were 2 to 15 times higher than outdoor concentrations. In other words, so that it sinks with us, the air within one of these buildings is extremely contaminated. Per unit area, building emissions of VOCs were comparable to traffic, industrial, and biogenic emissions.

“Buildings account for a significant fraction of the land area in cities and provide a significant amount of occupied indoor space,” said Dr. Tianren Wu, the first author of the study and an assistant professor at the University of Cincinnati. “To meet building ventilation and thermal comfort requirements, a substantial amount of air is actively exchanged between a building and its proximate urban atmosphere.”

As stated in their study, then, the office building studied was a significant source of reactive monoterpenes and siloxanes, which are chemicals commonly found in personal care products like deodorants, perfumes, and lotions. The study highlighted how these VOCs, once released indoors, are expelled into the outdoor environment through HVAC systems. Ventilation systems can be good at extracting these pollutants from the indoors and out to the outdoors.

What are the implications of the study, then?

This study has important implications for how we think about urban air pollution and the measures we take to mitigate it. Traditionally, efforts have focused on reducing emissions from vehicles and industries, and by all means, they should be. However, Boor’s research suggests that buildings should also be a key focus.

“The building source-sink behavior changed dynamically with occupancy and building ventilation conditions,” Boor explained. This means that the amount and type of pollutants emitted can vary depending on how many people are in the building and how the HVAC system is operating. All in all, things need to be evaluated better and handled better. But how?

To mitigate these emissions, the study suggests using carbon filters and other air-cleaning technologies in HVAC systems. Additionally, choosing consumer and personal care products with low VOC emissions can help reduce the impact. But this is something we could have all guessed. See the figure below, showcasing how these pollutants vary throughout the day.