Sun sets on bacteria-filled homes
Most of us dread doing the housework, all that cleaning and polishing only to find new dust layers starting to re-form almost immediately.
Luckily, new research shows that the best disinfectant for your dusty home might take a lot less elbow grease than constant buffing and could be as simple as opening your curtains.
We know that a little bit of sunshine on our skin is good for keeping us healthy by helping our bodies to produce vitamin D.
Now research published in the journal Microbiome has found that a little bit of sunshine on our homes could also keep them healthy by killing off the bacteria that can cause respiratory diseases.
Normal household dust can contain up to 9000 different species of microbes, including bacteria and fungi, as well as human skin dander and specks of insect carcasses.
This new study collected samples of dust from the vacuum cleaners of residential homes and sprinkled them into 11 identical tiny rooms that the researchers had specially built for the project.
Although the rooms were small at only 1/30th the size of a standard living room, they were carefully climate controlled to mimic the conditions found in real buildings and differed only by the types of windows they had installed.
Some of the windows were designed to transmit visible light, some only ultraviolet light and some let in no light at all.
After sprinkling the rooms with the dust, they were left for three months at normal room temperature to see what effect the type and amount of light the rooms were exposed to might have on the composition of the dust.
After 90 days the dust was analysed for amount and composition.
The researchers found that the rooms exposed to daylight contained only half the number of bacteria compared to the rooms that were left dark. Of the bacteria found in the dark rooms, 12 per cent were viable, meaning that they were alive and able to reproduce. This was double the amount of viable bacteria that was found in the sunlight rooms.
Most window glass is designed to block out some of the sun’s UV rays, however, this experiment showed that even the small amount that passes through was enough to halve the amount of viable bacteria in the dust.
UV rays have been shown to be germicidal by causing a chemical reaction which can eradicate bacteria
and viruses, and this study showed that just the act of exposing rooms to sunlight was powerful enough to inactivate some of the bacteria found in the room.
Importantly, the bacterial species that didn’t survive due to sunlight exposure included those related to Saccharopolyspora rectivirgula, which are known to cause respiratory disease.
As people spend more of their time indoors their exposure to dust particles that contain a variety of different microbial communities is high.
This new research shows that the simple act of opening the curtains on a sunny day and flooding rooms with sunlight could help to reduce the number of viable bacteria in the dust and in turn improve the health of the people living in the buildings.
A central component of architectural design – exposure to sunlight is often used by architects to change the feel of a room. Now building designers might want to maximise a room’s exposure to the sun’s rays to also influence the microbial communities living inside.
So the next time you are putting off dusting those shelves, open the curtains instead, knowing that even if the house doesn’t look any cleaner, at least the effort-free disinfectant power of the sun is sanitising the dust layers for you.
Dr Michelle Dickinson, creator of Nanogirl, is a nanotechnologist who is passionate about getting Kiwis hooked on science and engineering. Tweet her your science questions @medickinson