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30/09/2022
Since 2019, we have run a quiz on our twitter account where our followers guess which of the two items we have tested has the highest bacterial levels. Some of these results have been quite unexpected! Below we have listed everything we have tested for the quiz and the bacterial levels that they had. You may find that some results surprise you!
For reference, CFU = colony forming units.
Whilst the bacterial level was not as high as we expected, it's no suprise that over 13 CFU/cm2 of bacteria was found to be on this phone's screen. We touch our phones on average 2617* times a day transferring oils, dirt, skin cells and any bacteria we have picked up off other surfaces onto that shiny screen. With many phones being kept in pockets (where the temperature is usually a few degrees warmer than ambient), it's an ideal breeding ground for the bacteria.
*https://dscout.com/people-nerds/mobile-touches
The fridge has one of the most frequently opened/closed doors in your home. Every time you make a cup of tea or you get some food, your hands make contact with your fridge. While most of us would wipe down the fridge handle if it appeared visibly dirty (e.g. flour from baking), invisible microbes could be lurking there for weeks without being cleaned. The bacterial levels came in at 70 red spots which is slightly more than the iPhone screen that we tested.
Now we would all expect a public toilet to have higher than average bacterial levels and at 465 red spots, the results were no shock to us. However, what was interesting is the area we tested was the top of the tap handle (the area you push down to turn the tap off after you've washed your hands). It just goes to show that even if you wash your hands properly, you could easily re-pick up bacteria from the people who have used the tap before you. This shouldn't be an issue in public toilets that use automatic taps.
So even if you have taken time to wash your hands properly and somehow managed not to pick up bacteria from the sink tap, the hand dryer is your next obstacle. Every day, a hand dryer draws in large volumes of air (including the bacteria suspended in it) and usually passes these through a filter. If the filter is not replaced as scheduled, the bacteria could end up multiplying and being ejected at high speed onto your hands. If the hand dryer is in a moist envirnoment such as a gym changing room, this could provide an ideal breeding ground for germs to flourish. Of course not all hand dryers are created equal and some now include modern technologies such as UV.
The inside door handle having so many red spots implies that not everyone is washing their hands! This is the inside door handle of the entire public toilet, not just the individual cubicles. At 129 CFU/cm2, it was one of the highest bacterial contaminated surfaces we tested. This suggests that the inside door handle would benefit from regular cleaning throughout the day / week.
Beards can be dirty, right? This is something that used to be thrown around alot but in reality a well maintained / washed beard doesn't have the sort of bacterial levels you would expect. With only 50 red bacteria spots, it was on the lower end of all of our tests. This contradicts the beards are always dirty theory or are "Hazardous to human health" as one newspaper put it. Maybe our test subject takes really good care of their beard or we managed to test a non dirty area!
It is worth noting that this test was done on a pad with an adult owner (we suspect a child's game pad would have higher bacterial levels). However, the bacterial levels still came in at 92 red spots which is slightly higher than the phone screen. Considering how intense some games can be and how much the human hand can perspire, we would have still expected higher bacterial levels than this.
Interestingly, this one was a bit of a shock but on reflection, this potentially shows the power of UV rays. The steering wheel was leather, in a warm envirnoment but was also exposed to sunlight through the windscreen. We know that windscreens block a lot of UV rays, but not all. Side and rear car windows offer less UV protection so UV rays could have also penetrated through to the steering wheel this way.
Since bacteria thrives in sweat, it's not suprising that a yoga mat had a reasonable amount of bacterial colonies. Food for thought next time you're doing your childs pose! If you do regular yoga, our advice would be to wipe your mat down afterwards with an antibacterial / yoga mat cleaning spray. Not forgetting to allow it to dry (so you're not rolling up a wet mat which could make things even worse) before storing away.
Brushing your teeth is something you're taught from an early age will help clean your teeth and freshen your breath. "Kills germs and bacteria" is something major toothpaste brands are always using as a selling point in TV adverts. However, very few people do more than a simple rinse of their toothbrush after use let alone clean it. When was the last time you washed your toothbrush? This test goes to show that if you add water, a little heat (from the shower/bath) and time, bacteria will thrive. Regularly changing your toothbrush / toothbrush heads will help reduce the build up of microbes on your brush.
This test was completed in 2019 well before the pandemic. As such, it would be interesting to revisit this one to see if the levels are higher (since a lot of people have now switched to card payments) or lower (since many people now use contactless and won't be pressing bacteria covered buttons on a chip and pin machine). The good news is, with only 5 red spots, it was well below the bacterial level we expected.
All face creams should undergo a stability test and a challenge test to make sure that they can not only protect against bacterial growth, but also last the full duration of the stated shelf life. All good cosmetic companies not only do the above, but they also test each batch to make sure no ingredient has contaminated it (we actually sell cosmetic test kits for this purpose). However, every so often you will hear in the news of someone who has got an infection from makeup that had 'gone off'. Luckily in this face cream, bacterial levels were below the limit required for a Category 2 cosmetic product (in the UK).
This was a surprising one for us. We expected a high bacterial level but were shocked to see only 15 red spots. It may be due to the pond being reasonably new and possibly still having a high enough concentration of chlorine from the tap water to kill any bacteria.
Considering a key fob is likely to be pressed multiple times a day, a result of 17 red spots is not unexpected. Combine grease / dirt off of fingers with a warm pocket and you may have an ideal environment for bacteria to flourish.
There have been multiple studies of bacteria on money and interestingly they found that not only did money contain (in some cases) high levels of bacteria, but it also tended to contain bacteria specific to the envirnoment. Interestingly, Salmonella species, Escherichia coli and S. aureus are commonly found on banknotes from food outlets. In our test, the results were 70 red bacteria spots.
Along with a keyboard, a computer mouse is touched regularly during a working day. The frequency of this will of course depend on job type. Sometimes a computer and therefore also a computer mouse, may be shared and used by several people. The flipside of this is that some people are meticulous about cleaning their computer mouse. The bacterial level on this computer mouse didn't surprise us, we were maybe even expecting a little more than this!
Flag poles are open to the elements and are touched by some people who remove the pole from the hole (although not everyone will hold the pole in the same place). Bright sunlight can inhibit bacterial growth but rain / mud can do the opposite. It turns out that the area of the flag pole that we tested had very little growth.
A train toilet rail will probably be handled a lot as people try to steady themselves as the train is moving. Also this rail is right over the toilet which is prime position to pick up lots of microbes. As expected, the train toilet rail had a fair amount of bacteria!
Human bodies are home to countless microbes (good & bad). The nose in particular - a warm, moist environment offers the perfect conditions for bacteria. So it was no surprise that this nose had a very high bacterial count!
Office kettle handles are touched by multiple people throughout the day and probably aren't wiped all that often. As a shared appliance we expected there to be a moderate amount of growth on this and we were right. With items that several people come into contact with daily, it is probably worth regularly cleaning it to stop the build up of microbes (especially when in a kitchen environment).
Shoe laces obviously get handled a lot and get mud, soil, dust and rain on them frequently while outside. This sounds like a recipe for lots of bacteria to us! The laces did indeed have quite a few bacterial red spots on. If we had tested laces on a pair of walking boots or football boots, we suspect that the bacterial count would have been much higher!
Not one to compete with bacteria levels that would be seen on a general waste bin but it is a communal bin. This recycling bin is shared between several businesses so is touched by multiple people. The bin is positioned outdoors so the elements (e.g uv) could affect the result. The levels were relatively low which we believe is due to a combination of factors including sunlight and that it was a paper bin (so not heavily soiled items / food waste).
Car vents often have filters to help trap pollen, pollutants, dust etc. These filters help stop these contaminants / allergens coming through to the rest of the car when the heating / cooling system is activated. How often these filters are changed varies greatly and clogged / faulty filters can affect performance. In this case, the air from the vent in the car we tested was 17 red bacteria spots which is fairly low. If you ever get musty / stale smells coming from your heater / cooler areas in the car or if you've not done it for a while, it may be worth considering changing your filter.
We tested the buttons on a chip and pin machine in a popular pub and restaurant. This test was conducted in 2019 when less people were using contactless and a lot of people every day were pushing the buttons on this machine. As expected, the bacterial levels were really quite high. Since 2019, hand sanitisers are more in use, so this may yield much lower results if the test was done now.
Dog leads come into contact with humans, dogs, mud, rain, dust, streams - a whole mix of different particulates and microbes. Therefore, this was very much expected to have high bacterial levels. It did indeed, although not as much as the previous test (the chip and pin machine). This was the first of several animal related tests that we conducted that always seem to result in high amounts of red spots, as you'd expect.
We continued the pet theme with this one. A much loved cat toy - Freddie Purrcury. This toy has been cuddled, licked, sniffed and played with on many occasions. Cats are very clean creatures in regards to their grooming habits. However, like most animals, cats carry bacteria in their saliva and noses so anything that has been excessively licked is expected to have bacteria. Add to this, possible contaminants from outside, cross contamination from cat food & the fact that cat toys are difficult to clean, the results were always likely to be high. In this case, the levels were much higher than the dog lead.
Shoes come into contact with all sorts of microbes every day whether it be from dust, mud, rain, grass or just the daily pollutants and grime from pavements. People rarely clean the soles of their shoes unless they get excessively muddy. Due to this, we fully expected high levels for this and it was (even more so than the chip and pin machine by a very narrow margin).
Like the computer mouse from earlier, in busy offices, keyboards may be used by multiple people. Even if they are only used by one person, the keys are touched thousands of times a day. Add to this, general dust and bacteria in the air as well as any spillages and keyboards are great candidates for bacteria havens. The only thing that may impact bacteria levels in a positive way is that many people are more conscious of cleaning their devices now. This keyboard didn't have a large amount of bacteria, suggesting that it is cleaned on a fairly regular basis.
The kitchen can be a hub of activity in the office / workplace. A sink can become filled with tea bags and mugs or can be used as a receptacle to drain away dregs from someone's lunch or drink. Bacteria laden sponges may be left in the sink overnight or people may simply wash their hands in there. Whatever it's used for, a workplace sink is a wet area used by lots of people - perfect bacteria breeding ground territory. In this case, there were plenty of bacteria spots - almost as many as the chip and pin machine!
The adhesive strip on the envelope had been licked before closing. It was then sent through the post. Therefore, the test was conducted several days after it was initially sealed. Saliva does contain bacteria but the time during transit may have limited the amount of bacterial growth. The bacteria levels were exactly the same as the computer keyboard from earlier.
Being living, organic things, plants and their leaves contain all sorts of microbes. They have their own microbiome containing beneficial microbes but more harmful bacteria (to the plant) can also be present. In addition to this, will be general dust as well as microbes from watering and from the air. This pepper leaf had quite a few bacterial red spots, most of which will be perfectly harmless to this healthy plant.
Exposed to the elements, often purchased in busy supermarkets and with grooves in that can harbour microbes, we were expecting substantial levels on this. Cans that have been placed in a fridge will help stop microbrial growth so storing your can in a fridge or buying a can from a fridge, rather than a warm environment, may be a good idea. All this being said, very few people clean a can before drinking from it so the risk of harm is more than likely very low. The result was fairly high and was quite a surprise to our Twitter followers when it was revealed.
Potatoes spend the majority of their time in soil. Soil is teeming with microbes, most of which are beneficial. This unwashed potato was very likely to have a high amount of bacterial red spots. The result was indeed high, the highest result from any of our tests so far!
Wood is porous so is more difficult to clean than surfaces such as plastic or stainless steel. However, this also means that germs are less likely to sit on top of or transfer from wood as the porous surface is more likely to absorb microorganisms. Moisture which is needed for bacteria to thrive will also be absorbed into the surface, rather than sitting on top, which makes the surface less favourable to microbes. All this being said, the desk had fairly low bacterial levels.
Hair dryer handles may be touched daily by multiple members of a household. On the flip side, people usually use a hairdryer after they have just showered / bathed so should have fairly clean hands. However, most people don't clean their hairdyer handles often. It was a surprisingly high 499 red spots for the hairdryer which was a bit of an eye opener.
This was an interesting one that was suggested by one of our Twitter followers. You often see fingerprint marks on DVD / CD disks, they are usually touched by numerous people and are rarely cleaned. At the same time, they can be left for months without use and are often stored in a case where they are not going to pick up dirt. The DVD had 33 red spots which is a reasonable amount for something that may not be used often.
Drill handles come into contact with hands (which may be covered in diy related detritus), wood shavings, plaster and masonry dust as well as other related particulates. Drill handles are also never or rarely cleaned. This test resulted in 86 red bacteria spots.
Rubiks cubes are handled a lot and possibly by multiple people over and over again. This makes them an ideal candidate for high bacterial loads. This cube did come back with a fairly high result of 373 red bacteria spots.
We tested some flower vase water that had contained flowers for about a week. Water is obviously a big attraction for microbes. Add to that, organic material and plant matter from the flowers and this makes it a perfect environment for bacteria to thrive. Therefore, it was unsurprising that the flower water contained so much bacteria. In future, it may be worth giving your sink a quick clean after pouring your flower water into it.
Bike tyres come into contact with pollution particles, dust, mud, pollen, plant material and rain. Due to this, you'd expect to see quite a bit of bacteria on the tyre result. Surprisingly, although still fairly high, the test did not result in as many red spots as we expected. Proving yet again, that these tests are not as easy to predict as expected.
A cobbled path in a village with not a lot of footfall and not a lot of traffic so much smaller pollution levels than in a city. It is sometimes used by those walking for leisure who may have walked in fields with livestock. It would have the usual contaminants on it from shoes, rain, dust, wildlife but would also be exposed to the sun's UV rays. The path had 199 red bacteria spots. We suspect that it would be considerably more if it was a town or city footpath.
We tested a plastic construction barrier that had been open to the elements for months. It had been exposed to construction dust, rain and handling from multiple people. It was also exposed to sunlight during this time (which we have previously seen seems to affect the results quite considerably). The barrier had less bacteria than the cobbled path which was located very close to it.
We tested the inside of a toilet roll cardboard tube. These have been used a lot in the past for craft projects but in recent years, some people have stopped using them for 'hygiene' reasons. Due to this, it seemed like the perfect thing to test. We tested the inside of the tube as this will have been constantly exposed to outside elements. The tube had 29 red spots which although not as many as a lot of our tests, is still 5.8 colony forming units per cm2.
For this test, we used the dipslide on the outside of a banana skin. The banana skin was still on the fruit so was still fresh. It will have been exposed to microbes on its journey to the UK, as well as in the supermarket and in the household where it eventually ended up. As bananas are kept at room temperature, they offer a better environment for bacterial growth than fruit kept in the fridge. The banana skin had 80 red spots, so quite a bit more than the toilet roll tube.
Car engine oil was tested for this experiment. This was an interesting one as oil isn't water based so isn't as attractive to microbes. When the engine is running, the oil would be kept very hot. We think this may be a big contributing factor as to why there was only 1 red spot!
Glasses are exposed to the outside world, they also end up with smudges from fingerprints, make up, sun cream etc. People often wipe their glasses using a glasses cloth but most people don't actually clean their lenses on a regular basis. When not in use, a lot of people store glasses in a case, so they aren't likely to pick up much dirt when in storage. The glasses lens had quite a low bacteria result but regular, gentle cleaning would probably be wise.
Similarly to the glasses lens, watch faces are exposed to all sorts of environmental contaminants. As it is close to the hands, incidental contamination possibly occurs quite often. If we had tested a smart watch, this would almost certainly have had more red spots as the wearer would be touching it throughout the day. A lot of companies use different coatings on the glass on their watches (such as scratch resistant treatments). We do not know how these might affect the microbes ability to grow on these surfaces. The glass face had very few red spots. If we had tested the watch strap, we believe this would have been much higher.
We thought it might be interesting to test a cardboard box that had just been sent through the postal service. It would have come into contact with numerous people and would have been stored in and transported to and from several different locations. Cardboard is a more porous material so microbes don't sit on top of it for long. Despite arriving with us not long before the test, the results were quite low which is probably due to the porosity of the material.
This clementine was kept in a fridge which can significantly inhibit bacterial growth. It was also in a bag which means that it wasn't overly handled in the supermarket that it was purchased from. With it being in a fridge, it was expected to have less bacteria than the banana that we tested earlier and did so with 12 red spots instead of 80.
Freshly fallen snow is very cold and has not been stood on or soiled in any way. The cold does not provide conditions favourable to bacterial growth so we weren't expecting a lot of red spots for this one. There was only 1 red spot which is the same as the car oil.
The candy cane decoration is made of plastic. It does have lights in so may get slightly warm when these are activated. It was outside exposed to all of the elements - cold, rain and the winter sun. We weren't expecting massive numbers here but it did have a reasonable amount with 19 red spots.
As you'd expect with an object that is outside all of the time, solar panels are often covered by rain, dust and general dirt. However, solar panels are often hosed down / cleaned to improve their efficiency. Crucially they are placed in prime position to receive the suns rays which also means that they get very hot and are exposed to UV rays alot of the time. This is why we think the solar panels had a small number of red bacteria dots.
Copper has long been lauded for its antibacterial properties. However, 2 pence coins are in circulation for many years and are in the tills, pockets, wallets and hands of thousands of businesses and people. Therefore, a fairly high level of bacteria spots was expected. There were 77 red spots which isn't low but isn't especially high either so maybe there is something to be said for the antibacterial properties of copper.
Soil is teeming with bacteria - many which are beneficial and play a crucial role in the soil microbiome. Some of these are decomposers that help break down plant matter and pollutants in the soil. Some bacteria has a mutually benefial partnership with plants. Alot of the microbes found in soil have some benefits for the plants growing in it such as disease inhibition.* Basically, soil with lots of bacteria in it is healthy soil. This glove had just been exposed to soil and not surprisingly had a massive amount of red spots.
* https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/biology/?cid=nrcs142p2_053862
The footpath sign we tested looked quite old and weathered so has probably been out in the elements for a very long time. As we now know after conducting many tests on outdoor objects, been exposed to rain and dirt can often be counteracted somewhat by the sun's UV rays. This had 48 red bacteria spots which is a little surprising for something that looked quite old. However, it is wooden which is porous and moisture and microbes are often absorbed into the material quickly.
The inside of a sun hat after a lot of wear on a hot day can get quite hot and sweaty. As we know, sweat contains bacteria. The material on the hat would absorb moisture and would not have microbes sitting on its surface as long as a material such as plastic. This test resulted in 19 red bacteria spots which may not seem alot but we only test a small portion of the material. It is probably worth wiping the inside of your sun hats every so often to avoid a build up of dirt and bacteria.
As mentioned previously in this blog post, cats are clean animals that take personal grooming very seriously. However, a pet bed can become very warm and possibly damp, if they lay on it soon after grooming themselves. There's also the possibilty of contamination from cat food, treats or even the litter tray. The cat bed had quite a few red spots but not as many as the cat toy from earlier which came into contact the cat's mouth and nose frequently.
Dogs are lovely. Dogs also love running around in muddy puddles, waterways and rolling around in whatever takes their fancy at the time. Despite many dogs being bathed by their owners regularly, it's inevitable that a dog bed would have high bacteria levels. The dog bed had 107 more red spots than the cat bed.
We tested the inside of a nylon horse head collar. To be precise, we tested the bit that goes on the front of the face above the nose. Although horses don't wear horse head collars for long periods, with it being on the front of the face, this area is exposed to contaminants regularly (when feeding, nuzzling, grazing). The collar had 200 more red spots than the dog bed.
This electric car charger was tested on a very hot day. No doubt this would have an impact on results. It was at a service station so will have been used quite regularly but not as often as a petrol station hose. It was a low bacteria count which almost certainly was due to it being one of the hottest days of the year during the 2022 UK heatwave.
We tested just washed hands that were washed for 20 seconds with antibacterial soap and dried on a clean hand towel. The result was that there were 0 red spots. This does not mean that there was no bacteria. It just means, the amount was too low to detect on the dipslides. There will almost certainly have been some bacteria but it was very low levels in this case.
Similar to the clementine from earlier, this is a test on the skin of a soft fruit that was kept in a fridge. One difference is that the skin is much more textured (possibly allowing more grooves for microbes to congregate in). Another is that this avocado was loose and was not displayed or purchased in a bag. This may have contributed to the higher bacterial count.
Bacteria levels on a hoover handle are dependent on many factors such as how often a hoover is used, how often it is cleaned and where it is stored. The hoover handle result was very close to the avocado one, with it only having 6 extra red bacteria spots.
The dipslide was placed across the screen and some of the buttons for this test. Since these are both areas that regularly come into contact with hands, it was expected that there would be a high number of red spots. Compared to the phone and the console controller that we had tested previously, the colony number was a little lower.
The light switch was in a home office which is a communal space. It is used by several people but as the room is only used as an office, it is not switched on and off as regularly as other rooms in a domestic space. The switch had a similar number of colonies to the outdoor paper recycling bin handle that we tested.
Yoga blocks can be used with both the hands and the feet. They may be used multiple times in one class. The yoga block had a very high amount of colonies - more than a shoe sole and chip and pin machine buttons. Wiping down exercise equipment regularly is worth considering after this result!
This reusable bag is kept within a handbag / backpack when not in use. It is used regularly. We tested the outside of the bag. There may be a coating on the outside of the bag to keep it water resistant (which may affect how bacteria grows on it).
A small umbrella that is kept in a bag when not in use. Waterproof coatings on the material may affect microbe's' abilities to adhere to the surface which could partly explain the small number of colonies. Some of the bacteria may be washed away in heavy downpours. However, rain water is not sterile and contains microbes.
This tracker is attached to keys and is often in a pocket. Keys and trackers are not often cleaned / wiped as they can / do contain electronics within them and the user may not wish for them to become wet. The closest result to the tile was the beard that we tested which had 50 red spots.
This pedal had been used recently. The person wore house slippers to use it (not outdoor shoes). Despite the pedal being pressed lots of times when the sewing machine is in use, possibly due to the use of indoor footwear, the colony count was not as high as you might expect.
This is an exercise wheel for cats that is used by an indoor cat on a daily basis. The wheel is disinfected every 1 to 1.5 weeks. The indoor cat doesn't pick up bacterai from outside but does use an indoor litter tray which may help to explain the high number of colonies.
This small exercise weight is used in pilates and yoga classes. It is regularly wiped down with a cleaning wipe but was not cleaned after its last use and prior to testing (for the purposes of the test). As we've seen previously with the yoga block and yoga mat, exercise equipment can be a breeding growund for bacteria and this weight was no exception.
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