A well-lit room is joyful and cosy, but there is something else, it has also less bacteria, that normally live and grow in the dust. This is the result of a study carried out by a team of the Oregon University lead by dr Fahimipour. The research is available online in the open access journal Microbiome (Fahimipour et al, Microbiome, 2018, 6-1).
The scientists created 11 miniature rooms, able to reproduce exactly every characteristic, from temperature, to lighting and humidity, of a real house. Three types of glazing treatments were applied to the windows, one that transmitted visible light, another ultraviolet light and finally no light. These rooms were exposed for 90 days to dust collected in some real houses of Oregon. At the end of this period samples of dust were analyzed in order to study the viable bacteria, namely that alive and able to reproduce. What the scientists observed was that in the dust of the rooms let in the darkness the number of viable bacteria was twice the bacteria in the rooms exposed to light, in particular the dust in dark rooms contained 12% of viable bacteria, the dust of the rooms exposed to visible light 6,8% of bacteria and the dust exposed to ultraviolet light 6,1 %. Moreover, the dust in dark rooms contained organisms related to respiratory diseases that were practically absent in rooms with light. Other studies are needed to deeply understand the mechanism with which light removes part of the bacteria, but this research paves the way for interesting applications in order to guarantee a higher hygiene and health in closed buildings such as schools, offices or houses, where we spent most of our time.