Cooking, cleaning and other routine household activities generate significant levels of volatile and particulate chemicals inside the average home, leading to indoor air quality levels on par with a polluted major city, according to a study by researchers at the University of Colorado Boulder.

Furthermore, airborne chemicals that originate inside a house don’t stay there: Volatile organic compounds (VOCs) from products such as shampoo, perfume and cleaning solutions eventually escape outside and contribute to ozone and fine particle formation, making up an even greater source of global atmospheric air pollution than cars and trucks do.

Researchers from CU Boulder’s Cooperative Institute for Research in Environmental Sciences (CIRES) and the university’s Department of Mechanical Engineering presented their recent findings during a panel discussion at the 2019 AAAS Annual Meeting in Washington, D.C.

Homes have never been considered an important source of outdoor air pollution and the moment is right to start exploring that. We wanted to know: How do basic activities like cooking and cleaning change the chemistry of a house?

—Marina Vance, an assistant professor of mechanical engineering at CU Boulder

In 2018, Vance co-led the collaborative HOMEChem field campaign, which used advanced sensors and cameras to monitor the indoor air quality of a 1,200-square-foot manufactured home on the University of Texas Austin campus.

Over the course of a month, Vance and her colleagues conducted a variety of daily household activities, including cooking a full Thanksgiving dinner in the middle of the Texas summer.

While the HOMEChem experiment’s results are still pending, Vance said that it’s apparent that homes need to be well ventilated while cooking and cleaning, because even basic tasks like boiling water over a stovetop flame can contribute to high levels of gaseous air pollutants and suspended particulates, with negative health impacts.

To her team’s surprise, the measured indoor concentrations were high enough that that their sensitive instruments needed to be recalibrated almost immediately.

Even the simple act of making toast raised particle levels far higher than expected. We had to go adjust many of the instruments.

—Marina Vance

Indoor and outdoor experts are collaborating to paint a more complete picture of air quality, said Joost de Gouw, a CIRES Visiting Professor. Last year, de Gouw and his colleagues published results in the journal Science showing that regulations on automobiles had pushed transportation-derived emissions down in recent decades while the relative importance of household chemical pollutants had only gone up. (Earlier post.)

Many traditional sources like fossil fuel-burning vehicles have become much cleaner than they used to be. Ozone and fine particulates are monitored by the EPA, but data for airborne toxins like formaldehyde and benzene and compounds like alcohols and ketones that originate from the home are very sparse.

—Joost de Gouw

While de Gouw says that it is too early on in the research to make recommendations on policy or consumer behavior, he said that it’s encouraging that the scientific community is now thinking about the “esosphere,” derived from the Greek word ‘eso,’ which translates to ‘inner.’

There was originally skepticism about whether or not these products actually contributed to air pollution in a meaningful way, but no longer. Moving forward, we need to re-focus research efforts on these sources and give them the same attention we have given to fossil fuels. The picture that we have in our heads about the atmosphere should now include a house.

—Joost de Gouw