Within the grimy creases of our home,
Lurk microbes poised and floating in the dust;
A sullied sign that we are not alone.
We treat these scrounging tenants with disgust,
Yet most of them just want to co-exist;
To which our incensed manners seem unjust.
By letting sunlight stream into their midst,
We banish tiny lodgers from our sight;
And wash away all traces they exist.
Like stranded vampires in the dying night,
Our unseen guests cannot survive the light.
In this study, researchers built specially climate-controlled miniature rooms that mimicked real buildings and introduced dust that was collected in residential homes. The researchers then applied one of three glazing treatments to the windows of the rooms, so that they transmitted visible, ultraviolet or no light (i.e. a darkroom). After 90 days, the dust was collected from each environment and analysed. During this analysis, the researchers found that on average 12% of bacteria measured in the darkrooms were found to be viable (i.e. alive and able to reproduce), whilst for bacteria that was exposed to either daylight or UV light this figure was reduced to 6.8% and 6.1%, respectively.
The researchers in this study also found that a smaller proportion of bacteria that originated from human skin and a larger proportion of bacteria that came from outdoor air lived in dust exposed to light than in the dust that had not been exposed to light, suggesting that daylight causes the microbiome (i.e. the combined genetic material of the microorganisms in a particular environment) of indoor dust to more strongly resemble bacterial communities found outdoors. This research suggests that architects and lighting professionals designing building facades and rooms with more or less access to daylight may play a role in influencing the microbial communities of indoor dust. However, other factors like building occupancy, ventilation, and humidity need further investigation to better understand the complex relationships between environment and dust microbiomes.