Many of us worry about the germs lurking in our toilet.
But we should turn our attention to the kitchen instead, new research suggests.
A study has found we breathe in more bugs from our tap water than from our toilet.
Bacteria gathers on objects and surfaces in the home and travels into the air, circulating around our houses.
Californian researchers wanted to find out which objects or areas in our homes breed the most bacteria that is then released into the air that we breathe.
And they were surprised to find that tap water is an overlooked source of microbes, releasing a significant amount of bugs into the air.
More bacteria in the air in people's homes comes from their tap water (9 per cent) than their toilet (0.4 per cent), according to new research
One theory is that germs can escape from tap water into the air more efficiently than they can from other surfaces, including the toilet,
The researchers say studying how many microbes circulate around our homes is of 'critical importance' as we spend the majority of our time indoors.
The team, from the University of California, Berkeley looked at bacteria in the air of 29 homes in the San Francisco Bay area.
They took samples from kitchen surfaces, carpets, pets, bathroom tiles, shower heads, toilets and the people who lived there.
This was to show which surfaces contributed to the most bacteria entering the air.
Overall, the most common source of microbes was floors and carpets.
This was where nearly 20 per cent of microbes in the home came from, probably because walking across the carpet or vacuuming stirs up the bacteria into the surrounding air, the researchers said.
The next biggest source of bacteria was air from outside the home,
Some 17 per cent of germs came into homes this way, as people in California keep their windows open in the heat.
The study also found the number of bacteria increased significantly in homes that were ventilated frequently, as well as those with more family members, and where residents were more active.
The biggest source of bacteria in the air in the home comes from the floor and carpet (19.5 per cent in total), while very few germs come from counter tops and refrigerators (1.6 per cent and 0.8 per cent). Pictured is a pie chart of the main sources of airborne bacteria in the home
WHERE AIRBORNE BACTERIA IN THE HOME COMES FROM
Only 0.04 per cent of bacteria in the air in people's homes came from the toilet, a study found
Researchers listed the sources for indoor air bacteria in the homes:
Outdoor air: 16.5 per cent
Floor and carpet 19.5 per cent
Tap water: 8.8 per cent
Pets: 6.3 per cent
Doorstep: 5.6 per cent
Skin: 4.9 per cent
Showerhead: 4.1 per cent
Countertop: 1.6 per cent
Bathtub tiles: 1.5 per cent
Refrigerator: 0.8 per cent
Saliva: 0.6 per cent
Toilet: 0.6 per cent
Source: Microbiome journal
But this is actually a good thing, the scientists said, as fresh air brings in a fresh crop of microbes, blowing away the potentially harmful bugs growing in our homes.
The researchers had originally wondered whether flushing a toilet could spray bacteria from faeces into the air around the home - but they found only 0.04 per cent of microbes could be traced back to this source.
Surprisingly, nearly 9 per cent of airborne bacteria came from tap water.
Writing in the journal Microbiome, the researchers said: ‘Interestingly, tap water was indicated to be the third most important source of bacteria in indoor air.’
They added that kitchen counter tops, bathtub tiles, refrigerators, saliva, and toilets contributed very little to the populations of microbes in the air.
Bacteria seem to be able to escape from tap water into the air more efficiently than it can from other surfaces in the home, they concluded.
Dr Amy Pruden, of Virginia Tech University, told New Scientist that tap water has been overlooked as a source of bacteria
‘We drink a lot of it, we shower in it, and when we use a tap, water is aerosolised and we breathe it in.
‘There are a lot more bacteria in drinking water than people think.’
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