Sunlight may be best disinfectant, kills bacteria trapped in room’s dust

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Sunlight really may be the best disinfectant, as letting light into a house kills off the bacteria in household dust.

Letting natural light into a room destroys around half of living bacteria in dust, a study has found.

Sunshine could eradicate potentially harmful bugs linked to respiratory disease, and researchers say hospitals as well as families should take note.

Scientists at the University of Oregon, United States (U.S.), collected dust from household vacuum cleaners and left it in miniature rooms for 90 days.

The rooms were kept in darkness or had windows letting in sunlight and ultraviolet light.

When the dust was analysed, sunlight was found to have destroyed bacteria closely related to Saccharopolyspora rectivirgula.

More research is needed on whether this is harmful in household dust but Saccharopolyspora rectivirgula can trigger ‘farmer’s lung’ in agricultural workers, causing coughing and shortness of breath from the dust in mouldy hay.

Dr. Ashkaan Fahimipour, who led the research from the University of Oregon’s Biology and the Built Environment Centre, said: “We need a lot more research before we can apply this to real life but, based on our findings, I don’t see any harm in letting a little more sunlight into our homes.

“There are a lot of procedures to prevent infections in hospitals already and in future we might also suggest sunlight as a cheap and easy measure to take.”

For their experiment, the US researchers created 11 climate-controlled rooms approximately one thirtieth the size of a household living room, at 14 feet (4.3 metres) wide.

Household dust, collected from the vacuum cleaners of ordinary homes, was placed in petri dishes within the rooms.

That dust was exposed to sunlight through a window, UV light filtered from outside or to complete darkness from an aluminium plate placed over the window.

Three months later dust samples from dark rooms had 12 per cent of bacteria alive and able to reproduce, compared to only 6.8 per cent of dust bacteria exposed to daylight and 6.1 per cent exposed to UV light.

Dust left in the dark contained more bacteria from human skin and less from outside.

The results suggest sunlight is a ‘bactericide’ which can destroy bugs, according to the study published in the journal Microbiome.

It may cause a chemical reaction which eradicates the micro-organisms.

Scientists monitored the dust for 90 days to reflect how long it typically stays in our homes before being cleaned away during housework.

Dr Fahimipour said: “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.

“Humans spend most 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.”

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