Sunlight Can Help Kill Germs In Your House, A New Study Says

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If you’ve ever heard that old wive's tale that letting plenty of sunlight into your home is healthy, a new study shows that you should definitely open your blinds. According to research recently published in the journal Microbiome, sunlight can help kill germs in your house. Turns out there's a new, legit health reason why you'd want lots of natural light in your apartment.

Natural light has about eleventy-million benefits — it can help alleviate symptoms of Seasonal Affective Disorder (SAD), and it helps your houseplants thrive, which have air-quality-boosting benefits of their own. (Plus, obviously, natural light boosts your apartment's Instagrammability by a ton.) But this new research shows that natural light can also clean up the air in your apartment naturally, and that's pretty cool news heading into cold and flu season.

Researchers at the University of Oregon devised a model of 11 dust-ridden, doll-sized rooms, and analyzed what happens when indoor areas get exposed to sunshine. They compared natural light exposure via regular glass windows, rooms exposed to ultraviolet light only, and rooms kept dark, NPR reports. Dust was collected from homes throughout the Portland area, and researchers kept the insides of the dusty, miniature rooms at room temperature for 90 days in order to simulate real-world dust accumulation.

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After examining the mini-rooms after the 90 day test period, the study’s authors found that those rooms exposed to daylight had fewer germs than those kept in the dark. The researchers found that “light exposure … led to lower abundances of viable bacteria,” and that those rooms exposed to direct natural light had fewer germs.

NPR further notes that researchers analyzed both direct sunlight and UV light, as UV light is already proven to be an effective disinfectant (it’s often used to disinfect water). That said, most glass installed in homes filters these rays out. Well + Good reports that not only did the sunlit rooms have half the germs of the light-deprived rooms, rooms exposed to ultraviolet (UV) light only were slightly cleaner than the naturally lit rooms — they showed the lowest bacteria levels overall. Ashkaan Fahimipour, lead study author and a post-doctoral researcher at the University of Oregon’s Biology and Built Environment Center, told NPR that the fact that both UV and visible light were equally as effective for busting up bacteria was surprising.

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“Until now, daylighting — illuminating a building with natural light — has been about visual comfort or broad health. But now we can say daylighting influences air quality,” study co-author Kevin Van Den Wymelenberg, co-director of the Biology and Built Environment Center at the University of Oregon, told NPR. The study’s authors further noted that, in the future, they’d like to design studies measuring just how much light is needed to kill germs, so that buildings can be designed in order to better kill microbes.

When it comes to eradicating germs and microbes through standard cleaning methods, “Sanitizing isn’t the best approach,” Fahimipour told NPR, because, as it turns out, it’s actually pretty difficult to get totally rid germs without the help of daylight exposure. And Fahimipour also noted that some microbes are actually good for us. So, no need to fret too much about whether or not your apartment is clean enough. More research is needed to better understand just how much light is required to effectively kill germs. For now, just stick to your usual cleaning routine — and make sure to let as much natural light into your apartment as you can.