Letting The Sunshine In Can Kill Disease-Causing Bacteria Indoors

Findings of a new study suggest that failing to open the curtains or the windows in the home or office can make people prone to illness. The research also supports the wisdom of old folks who have long claimed that rooms exposed to daylight tend to have fewer germs.

The research, which was published in the journal Microbiome on October 18, found evidence suggesting that sunlight can kill disease-causing bacteria that live in the dust. Darker conditions, on the other hand can allow these pathogens to thrive and even reproduce.

Study researcher Ashkaan Fahimipour, from the University of Oregon, and colleagues, created 11 identical miniature rooms that allowed in different levels of light.

After 90 days, the researchers found that in dark rooms, 12 percent of bacteria on average were alive and able to reproduce. Only 6.8 percent of the bacteria exposed to daylight and 6.1 percent of bacteria exposed to UV light, on the other hand, were found viable.

The rooms exposed to sunlight also had less types of bacteria associated with human skin, which people typically shed when they move around indoors. The bacteria also more closely resembled outdoor air-derived bacteria.

Some of the human-derived bacteria that did not survive in the lighted rooms are from a family of bacteria known to cause respiratory diseases. This could mean that letting the sunlight in could actually help reduce people’s odds of contracting diseases.

The researchers said that the findings support the century-old wisdom that daylight can potentially kill microbes on dust particles.


“Light exposure per se led to lower abundances of viable bacteria and communities that were compositionally distinct from dark rooms, suggesting preferential inactivation of some microbes over others under daylighting conditions,” the researchers wrote in their study. “A small number of microorganisms may have exhibited modest population growth under lighting conditions.”

According to NPR, the researchers wanted to design more studies that could help determine how much light is needed to kill microbes. These could help architects design healthier homes and buildings.

Fahimipour explained that humans spend most of their time indoors so exposure to dust particles with different types of bacteria, including those that can cause illness, is unavoidable.

“We hope that with further understanding, we could design access to daylight in buildings such as schools, offices, hospitals and homes in ways that reduce the risk of dust-borne infections,” Fahimipour said, according to Science Daily.

“It is important to understand how features of the buildings we occupy influence dust ecosystems and how this could affect our health.”