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Sunlight may kill dust-dwelling bacteria
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Researchers found that letting sunlight in through windows can kill bacteria in dust around the same level as ultraviolet light.
“Humans spend much of their time indoors, where exposure to dust particles that carry a variety of bacteria, including pathogens that can make us sick, is unavoidable. Therefore, it is important to understand how features of the buildings we occupy influence dust ecosystems and how this could affect our health,” Ashkaan K. Fahimipour, PhD, for the University of Oregon’s biology and built environment center, said in a news release.
For their study, Fahimipour and colleagues constructed 11 identical built environment microcosms — climate-controlled miniature rooms — based on typical residential and nonresidential rooms, each a 1:32 scale of a rooms measuring 4.3 m wide, 7.9 m deep, 3.3 m tall, and with a single 3.5 m x 1.2 m window and a 1 m sill. Nine of the “rooms” had windows treated with one of three glazes that transmitted mostly visible, ultraviolet or no light.
The two remaining rooms were equipped with sensors to measure hourly dosages of light throughout the room, with one to measure visible and the other to measure UV wavelengths. In addition, the total exterior light was measured by sensors was placed on each roof. All rooms had temperature sensors to ensure that the interior stayed between 18.19°C and 22.34°C — the typical range of temperature in buildings. Household dust was placed in each room for a 90-day exposure period — the estimated amount of time dust particles live in buildings that are regularly cleaned, according to the researchers.
The study found that dust exposed to sunlight was relatively free of bacteria from the genus Saccharopolyspora, which was abundant in the dust of rooms with no light and is associated with respiratory diseases. Moreover, although 12% of bacteria in dark rooms were alive and viable, only 6.8% of bacteria exposed to sunlight and 6.1% exposed to UV light were viable. Researchers also found that dust exposed to sunlight had fewer bacteria derived from human skin and more derived from outdoor air, suggesting that sunlight may cause the microbiome of indoor dust to appear more like outdoor bacterial communities.
“Our study supports a century-old folk wisdom, that daylight has the potential to kill microbes on dust particles, but we need more research to understand the underlying causes of shifts in the dust microbiome following light exposure,” Fahimipour said. “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.” – by Erin Michael
Disclosures: The authors report no relevant financial disclosures.
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