Part Those Curtains: Letting Sunlight In Your House Actually Kills Germs

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Sunshine can help kill germs in dust

Open those curtains, raise those shades, and maybe consider installing that skylight you’ve always wanted. A new study conducted at the University of Oregon has found that sunlight, even when filtered through glass, kills a significant amount of germs found in household dust. The findings suggest that letting light into our homes is good for yet another reason — and that sunning your rooms could help fight issues like poor air quality, infections and respiratory disease.

The study, which was published in the scientific journal Microbiome this week, constructed several dollhouse-sized rooms and filled them with a mix of dust collected from local houses. The houses were then exposed to either darkness, UV light, or sunshine for 90 days , the amount of time that dust can stick around your house, even if you are vacuuming regularly.

The results found that rooms exposed to sunlight, even through closed windows, had just half of the living bacteria that dark rooms had, and that the sun-soaked rooms killed off just as much bacteria as UV light, a known disinfectant.

The study’s lead author, Ashkaan Fahimipour, is a postdoctoral researcher at the University of Oregon’s Biology and the Built Environment Center, while co-author Kevin Van Den Wymelenberg is the co-director of the Biology and the Built Environment Center at the University of Oregon.

They found that 12 percent of bacteria in the unlit rooms were alive after 90 days compared to 6.8 percent of germs in lit rooms and 6.1 percent in UV light rooms.

Van Den Wymelenberg explained that, “six percent of millions of cells is still a lot of microbes. Until now, daylighting has been about visual comfort or broad health. But now we can say daylighting influences air quality.”

Light and sun have a number of health benefits. Natural sunlight boosts Vitamin D, which is an anti-inflammatory linked to lower blood pressure, stronger muscles, and better brain functioning. Sunlight has also been linked to happiness and better sleep quality.

Now we know it can also help keep our homes, businesses, and hospitals healthier, less germ-y environments.

“I think it’s a novel study because they looked at the effect of visible light, and they were also looking at real bacterial communities and real household dust,” Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, told NPR.

The study also found that sunlight kills bacteria associated with human skin flakes, which make up a significant amount of dust. This specific type of bacteria is associated with respiratory disease — and eliminating them in indoor environments could improve air quality.

There was no word on how this study jives with research that shows how dirt and germs are good for our kids, though Fahimipour said that he envisions a future where we can eliminate or better control harmful bacteria, while promoting “good” bacteria that we benefit from.