One hundred and twenty years ago, in her ‘Notes on Nursing’, Florence Nightingale wrote about the benefits of allowing sunshine into a patient’s room. Since then many studies have shown that exposure to ultraviolet light can inactivate many bacteria. However, the windows used in most buildings only allow visible light though and block a large percentage of ultraviolet light. Now, a team of researchers from the University of Oregon have analysed the effect the Sun has on bacteria found in dust particles. By contaminating climate-controlled scale model rooms with a sample of dust combined from the homes of various volunteers, they looked at the effect different window glazes had on the bacteria present. They found that in rooms that had no light 12% of bacteria were viable, while this was only 6.8% in rooms exposed to daylight, and 6.1% in rooms that were exposed to ultraviolet light (and not visible light). Interestingly it was bacteria species that are associated with respiratory diseases that were mainly absent when exposed to daylight/UV light.
This study is only a starting point – the rooms created were experimental and only covered a small range of light dosages, and the impacts of daylight exposure on bacteria compared to other things, such as ventilation or humidity, is unclear. Designs of future schools, offices, hospitals, etc. may want to take into account the amount of daylight that can penetrate rooms.
— Peter Chilton, Research Fellow
- Nightingale F. Notes on Nursing. What it is, and what it is not. 1898.
- Fahimipoiur AK, Harmann EM, Siemens A, et al. Daylight exposure modulates bacterial communities associated with household dust. Microbiome. 2018; 6: 175.