Key Points:
- Dirty windows can harbor potentially harmful pollutants under protective films of fatty acids from cooking emissions, according to a new study.
- Fatty acids contained within cooking emissions are highly stable and not easily broken down in the atmosphere.
- Ozone, a key pollutant both indoors and out, altered the surface of the protective films.
The dinner you cook tonight may stay on your kitchen windows for years, according to a new study by researchers at the University of Birmingham. According to the team, the fatty acids contained within cooking emissions not only cling to hard surfaces for long periods of time, but also inadvertently form protective films to cover potentially harmful pollutants.
Once fatty acids hit a solid surface, such as a window, they form a self-organized thin film that builds up over time, only very slowly being broken down by other chemicals in the atmosphere. During this process, the film becomes rougher and attracts more water from the humidity in the air. Toxic pollutants can then become trapped underneath this persistent crust and are then protected from breakdown in the atmosphere.
“The fatty acids in these films are not, by themselves, particularly harmful but because they are not being broken down, they are effectively protecting any other pollutants that might be trapped underneath,” said senior study author Christian Pfrang.
For the study, published in Environmental Science Atmospheres, the researchers engineered material proxies that were then spun into super-thin films of pollution. Pfrang and his team used both neutrons and X-rays to study the nano-scale composition of the films and the changes in their surface structures. By changing the humidity and amount of ozone—a key pollutant—the researchers were also able to mimic the behavior of the films over time.
They found that the self-organized arrangement within the films in repeating molecular sheets made it difficult for smaller molecules, like ozone, to access the reactive parts of the fatty acids within these structures. Once deposited and exposed to ozone, the surfaces of the films became less smooth and increasingly likely to take up water, an effect that also has implications for the formation and lifetime of aerosols in the atmosphere.
Information provided by University of Birmingham.