Cleaning windows is probably no one’s favorite activity, but it’s a useful one. It’s not just that filth and mold can accumulate on or around the window, but another problem comes from cooking, a team of researchers found.

According to researchers from the University of Birmingham and the University of Bath in the UK, when you cook, fatty acids are emitted into your house. The substances are very stable and not easily broken down, so when they hit a surface like a window, they create a resilient film. This film can also trap toxic pollutants underneath, and herein lies the problem.

The fatty acids are not dangerous themselves, it’s the pollutants they trap that are. In time, parts of the film can naturally break down, releasing toxins. In order to reach this conclusion, scientists worked on lab samples that mimicked the real thing. They used neutron scanning and X-rays to analyze the nanoscale composition of the films that accumulated on windows and found that by changing the amount of humidity and ozone in the lab, they can mimic the behavior of the film in time.

Aerosols contribute to ambient air pollution, and in many parts of the world, organic compounds dominate aerosol composition (although this can vary with season and from place to place). However, poor air quality is linked to an increased amount of organic compounds in aerosols. The study of the effects of these organic compounds is therefore important if we want to understand the impact of particulate pollution.

Our houses in particular contain more pollutants than you’d expect — and this study shows that grimy windows could be one of the factors contributing to this pollution.

“We carried out simulated atmospheric processing (humidity change and oxidation) on nano-scale films of a semi-solid organic surfactant aerosol proxy,” the researchers write in the study. “The atmospheric lifetime of such materials is affected by the phase state, impacting the climate and urban air quality.” Basically, once the films are set up, they can keep pollutants in place and gradually release them into the indoor environment.

“The persistence of such semi-solid surfactant arrangements in the atmosphere has implications for the climate as well as urban and indoor air pollution.”

It’s not the first time research has drawn attention to the pollution inside our hoses. Cooking in particular has been linked to air pollution and the world’s poorest are often the most affected. This new study goes to show that there are still many mechanisms we don’t understand but ultimately, more research is needed to truly understand the effects of the interactions on our health.

Journal Reference: Adam Milsom et al, The evolution of surface structure during simulated atmospheric ageing of nano-scale coatings of an organic surfactant aerosol proxy, Environmental Science: Atmospheres (2022). DOI: 10.1039/D2EA00011C