Life is a dirty word. No matter how you live yours, you are exposed to filth daily. According to microbiologists, your home is riddled with dangerous bugs, as is your workplace.

Once you start digging for dirt, it’s hard to stop. Here are some findings from the most recent research. Swimming pools harbour faecal and urine contaminants; take a dip and you might pick up the Citrobacter freundii bacteria, an agent of infections such as pneumonia. The hot tub is another bubbling broth of bacteria, and has been linked to deaths from Legionnaire’s disease and pneumonia. Gyms are dripping with other people’s stale sweat and bacteria: Staphylococcus epidermis, which causes skin infections, streptococcal infections, and candida, a yeast infection, to name but a few. Germs, we are told, loiter in the most unlikely places; the herpes virus and those listed above can be a risk if the sweat of an infected person gets on to light switches, door handles, escalator handrails and any other frequently touched surfaces. Cold and flu viruses are also easily transmitted through touch. Some germs, such as enterococcus, survive for just 40 minutes, but most can linger menacingly for anything from 24 hours (Staphylococcus aureus, salmonella) to two to three weeks (rotavirus, hepatitis A and clostridium).

Charles Gerba, a professor of environmental sciences at the University of Arizona and an expert in the study of nasty bacteria that lurk in our lifestyles, found, for instance, that one of the most germ-ridden items in public spaces is the ground-floor button on a lift. But germs are not just spread by obvious means such as touch. They are insidious, creeping into every nook and cranny of our daily existence. Another of Gerba’s findings revealed how 30 per cent of women’s handbags contain 100 million particles of faecal matter per square inch on their surface, probably from being placed on the floors of public toilets. Kitchens and the implements they house are other prime breeding grounds. Surveys by the Hygiene Council (HC), a panel of the world’s leading microbiologists and virologists, indicate that 85 per cent of public toilets were cleaner than the average kitchen worktop in a British home.

Professor Hugh Pennington, an infection expert at the University of Aberdeen, would “like to get rid of washing-up bowls altogether; they are a menace”. Bathtubs often contain faecal particles “as people sit in them with dirty bottoms and don’t clean them afterwards”. Office desks are crawling with germs, as are the mobile phones used by 55 million Britons every day. Microbiologists say that the constant handling of a mobile combined with the heat generated from its battery allow bugs such as Staphylococcus aureus, which can cause everything from pimples to pneumonia, to spread like wildfire.

The list of warnings about public and private cleanliness – or lack of it – and its effect on our health seems endless. But does it really matter so much, or are scientists overreacting, triggering environmental paranoia in a society already burdened with one health worry too many? Professor John Oxford, a virologist at St Bartholemew’s and the Royal London Hospital, thinks not. “Experts are genuinely concerned about the spread of infection and disease through a lack of hygiene in this country as in others,” he says. “Exposure to dangerous germs is much more common than people think. Every day people come into contact with microorganisms in food, and faecal and oral contaminants spread through a lack of personal hygiene. Many microbes are using the opportunity to spread as never before.”

One person in five will suffer from diarrhoea this year and many more will get colds, flu and other viruses that have been transmitted through everyday germs and grime. It is easy to blame environmental health services and inefficient public health systems, but much of the problem lies with our own habits. We stroke pets, change nappies and sneeze without performing the most basic but effective bug-fighting practice: washing our hands. Hands are the primary carriers of pathogens such as salmonella and E coli. In theory, says Oxford (who is also the HC’s chairman), washing hands well, and often, could prevent the spread of everything from colds to MRSA.

What concerns experts is that complacency about hand cleanliness is increasingly responsible for the spread of illness in developed countries. It is known that viruses can survive on human hands for several hours and can be transmitted by direct contact. In October the HC is setting official hand-washing guidelines, urging people to wash their hands five to six times a day and more frequently if someone in the household or workplace has an infection.

On the flipside is the growing number of people who have become so fearful of the messages about poor hygiene that they develop obsessions about cleanliness. Kevin Gournay, a professor of psychiatry at the Institute of Psychiatry at Kings College London, says that obsessive compulsive disorder (OCD) affects 2 per cent of the population to the degree that it has become a significant handicap in their lives, and many more who find it disruptive. Of those, a “significant number” are obsessed with germs and dirt.

“There are varying degrees of OCD, from people putting tissue on toilet seats before using them or washing coins that they fear may have been contaminated to those who carry out rituals such as washing their hands 50 times a day,” Gournay says. “In extreme cases they have irrational fears such as concerns that they might catch Aids from microscopic spots of blood, even though they aren’t having sexual intercourse.” What all sufferers probably have in common, he says, is a biological propensity for OCD. “But the culture and environment we live in, where we are constantly told that things are too dirty and that we need to use antiseptics, chemical cleaning agents and wipes to r e m a i n s p o t l e s s , serves to exacerbate this propensity. It might start with someone washing his hands but never feeling clean enough.

“So he washes his hands, then uses a cleansing wipe. Then that becomes insufficient, and the problem gets out of control.” Stress and anxiety make it worse. Treatment for severe cases of OCD involves cognitive behaviour therapy and antidepressant drugs. “These people have to be exposed to gradually increasing amounts of dirt and grime until they become less anxious about it. It can take time.”

There are, of course, theories that we can be too clean, that all the antibacterial cleaning products we use are dulling our immune systems to the point where they no longer know how to fight bacteria. Many experts blame increasingly sterile environments for the increase in serious allergies, which have risen by more than 25 per cent in the past four years, according to reports based on Department of Health data obtained from GPs’ surgeries. Some 12.2 million people in England have had allergies such as eczema, asthma and hayfever diagnosed. Yet children who grow up on farms or have several older siblings – each of whom brings home germs a n d grime – are said to be considerably less at risk.

Even conditions such as diabetes have been linked to a lack of exposure to germs during childhood. At Scripps Research Institute, in California, scientists proposed that coming into contact with too few bacteria during childhood meant that the immune system was understimulated, creating a condition, lymphopenia, in which there is a reduction in the number of the body’s T-cells. People with type 1 diabetes, rheumatoid arthritis and lupus are known to have low levels of such cells, and the Scripps team suggested that “priming” the body with germs might reduce the chance of someone becoming ill later in life. Other studies suggest that there are enough T-cells, but they are not equipped to fight infection because they haven’t “met” enough germs.

However, Oxford dismisses the extreme cleanliness hypothesis as “scientific tosh”. “Nowhere is too clean and it is misleading to suggest that to the public,” he says. “People are getting ill because they are exposed to an ever-increasing number of germs.”

The issue of cross-infection, spreading viruses via unwashed hands, is high on the Government’s agenda as it realises that it is vital in the prevention of flu epidemics. Still, Oxford says, we should not become “too obsessive” about cleanliness. “People should target their hygiene habits, focusing on their hands, the kitchen and bathroom. That could be the best thing you do for your health.”

Offices

Professor Charles Gerba, of the University of Arizona, has uncovered some dirty secrets of the average workplace. Phones, PC keyboards and mice all harbour germs. “Desks are really bacteria cafeterias,” says Gerba, “capable of supporting ten million microbes. The average office contains around 20,961 per square inch compared with 49 in a toilet bowl.” He found that teachers had the grubbiest desks, lawyers the cleanest.

Gerba discovered that levels on keyboards peaked at 3,295 per square inch after lunch had been eaten at the desk: “If not cleaned, the keyboards could support millions of bacteria, which could cause illness such as gastrointestinal upsets.”

Computer mice harboured 1,676 particles per square inch, and both mobile and landline handsets could be health hazards because of the bacteria they contain. Microbiologists at Manchester Metropolitan University say that 26,000 microbes are crawling on every square inch of the average handset. Bugs found on phones include staphylococcus, which can cause pneumonia.

Toilets

Toilet bowls in people’s homes are usually so clean that “you could eat your dinner out of them”, says Professor John Oxford, a virologist at St Bartholemew’s and the Royal London Hospital.

But public conveniences are a different story. A study conducted by the University of Arizona found that the most common microorganisms associated with outbreaks stemming from public toilets included shigella, salmonella, norovirus and hepatitis A virus. Bacteria and viruses are ejected and dispersed into the air when a toilet is flushed; these germ-filled droplets land on all surfaces, contaminating the environment.

Researchers found that 64 per cent of the time the floor in front of the toilet in a public convenience was contaminated with faecal bacteria. For sinks the figure was 61 per cent of the time; for the top of the toilet, 20 per cent; and for the toilet handle 6 per cent.

Women’s toilets were significantly more contaminated than men’s, with the middle cubicle usually the most contaminated of all. Airport toilets were the germiest of all.

Gyms

Dr Derren Ready, a clinical scientist in microbiology at University College Hospital in London, analysed swabs taken from an unnamed London gym and found dangerously high levels of bacteria. “One site harboured 132 million bugs in an area the size of a 2p coin, while the average count was 16 million,” he says. On the bench-press headrest and dumbbells he found plenty of Staphylococcus epidermis, which causes skin infections. Sweaty residue on gym equipment used in quick succession, such as weights and exercise bikes, could also harbour streptococcal infections and candida. The sauna was the most bug-ridden place, with high levels of Citrobacter freundii, which can cause pneumonia, and blood and urinary-tract infections.

“It usually lives in the gut and its presence indicates faecal contamination,” Dr Ready says. He suspects that the high bacteria count could stem from the wooden benches in saunas and steam rooms; these have “lots of crevices, which are ideal gaps in which bacteria can colonise”.

Swimming pools

A recent survey by Which? tested 80 pools in Majorca and Corfu and found that most were laced with sweat, urine, mucus, saliva, hair, faecal matter and dead skin. Other studies have shown that outbreaks of cryptosporidium, which can cause vomiting and diarrhoea, may be linked to pools, while acanthamoeba causes painful inflammation of the eye. And the overuse of chemicals such as chlorine can irritate eyes and skin.