Our shoes are crawling with dirt (sometimes dangerous)

• Our shoes sometimes “host” drug-resistant pathogenic microorganisms, according to our partner The Conversation.

• The potentially dangerous E. Coli bacteria, for example, is so widespread that it can be taken from… 96% of shoe soles!

• This analysis was conducted by Mark Patrick Taylor, environmental scientist and Gabriel Filippelli, professor of Earth sciences.

You probably clean your shoes as much as you can if you're walking in something muddy, slimy or nasty (please pick up after your dog!)… But when you get home, do you always take your shoes off at the door? ?

The majority don't… Who thinks of what he drags under his soles when he finally returns home?

I'm part of a team of environmental chemists and we've spent a decade studying indoor spaces and the contaminants people are exposed to in their own homes.

Although our review of the indoor environment, via our

program , is still far from complete, on the question of whether to put on and take off shoes at home, science still has an idea.

It's best to leave your dirt outside the house.

•  ​Where do the contaminants found in our interiors come from?

  
  

• People spend up to 90% of their time indoors.

  The question of whether or not to wear shoes at home is therefore not trivial.

• Policies generally focus on the external environment in terms of soils, air quality and environmental risks to public health.

  However, regulations are now also increasingly concerned with the issue of indoor air quality.

• The material that accumulates inside your home does not only include dust and dirt brought in by your visitors, or the hair left behind by your pets: about a third comes from outside, brought either by the wind , or by the soles of dirty shoes – capable of picking up anything lying on the floor.

• For the latter, we are not talking about simple dirt but sometimes microorganisms such as drug-resistant pathogens, including infectious agents (germs) associated with hospitals that are very difficult to treat.

• Add to that the carcinogenic toxins from asphalt residue and the endocrine disruptors from lawn chemicals, and you might see your shoes in a different light.

• 
  

• Chemicals, carcinogens, contaminants can be brought back from the street or from the garden © Juicy FOTO / Shutterstock (via The Conversation)

•  ​A quick tour of the worst indoor contaminants

  
  

• Our work consisted of measuring and evaluating exposure to a whole series of harmful substances present inside homes, including the following:

• Antibiotic resistant genes (genes that make bacteria resistant to antibiotics),

• Disinfectant chemicals in the home environment,

• Microplastics,

• Perfluorinated chemicals (or PFAS, dubbed "eternal chemicals" because of their long lifespan and tendency to stay in the body without degrading) used ubiquitously in a multitude of industrial, household and packaging products food.

• Radioactive elements.

Assessing the levels of potentially toxic metals (such as arsenic, cadmium and lead) in homes in 35 countries (including Australia and France) is a major focus of our work.

These contaminants – especially lead, a dangerous neurotoxin – are odorless and colorless.

So there's no way to tell if the dangers of lead exposure are only found in your outdoor floors or water pipes or if they're also on your living room hardwood floors.

Our studies nevertheless suggest the existence of a very strong link between the lead present in your home and that present in the soil of your garden.

The most likely reason for this relationship?

Drafts, shoes and other dog and cat paws that bring them indoors...

Anticipate problems to avoid them

Hence the importance of making sure materials from your outdoor environment stay where they are (we have advice here, e.g. mop or damp cloth instead of sweeping or dry dusting, wash other than work or dust-laden clothing, etc.)

A recent

article argues that home shoes aren't so bad.

The author pointed out that E. Coli – a potentially dangerous bacterium that particularly thrives in the intestines of many mammals, including humans – is so widespread that it is present everywhere.

It is therefore not surprising that it can be taken from shoe soles (96% of shoe soles, as the article points out).

But let's be clear.

While it's nice to be scientific and stick with the term

, this bacteria, to put it bluntly, is associated with poo…

Whether it's ours or Medor's, it can make us very sick if we're exposed to it at high levels.

And let's face it, it's just gross.

Why walk her inside your house if you have a very simple alternative: take off your shoes at the door?

Indoor slippers: THE solution © Anna Mente / Shutterstock (via The Conversation)

​Prefer it "without shoes"

Are there any downsides to having a house without shoes?

Beyond the occasional squashed toe, from an environmental health perspective, there aren't many downsides to abandoning boots and pumps at the entrance to your home.

Leaving your shoes on the doormat also leaves potentially dangerous pathogens at the door.

We all know that prevention is much better than treatment.

Taking off your shoes is a basic and easy prevention activity for many of us.

Do you need shoes, insoles to support your feet?

It's simple: prefer the slipper or the "indoor shoe" never worn outside.

There remains the question of the “sterile home syndrome”, which refers to the increase in allergy rates in children.

Some claim it is linked to overly sterile homes.

Indeed, a little dirt is probably beneficial, since studies indicate that it helps to develop the immune system and reduce the risk of allergies.

Our "HYGIENE" file

But there are more effective and less disgusting ways to do this than walking around indoors with dirty shoes… Get outside, take a walk outside, enjoy the fresh air!

It is therefore useless to bring home polluted particles, animal waste or various pathogens which will accumulate and contaminate kitchens and bedrooms perceived as havens of peace and security.

Science

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Health

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This analysis was written by Mark Patrick Taylor, Environmental Scientist at the Environmental Protection Authority of Victoria, Honorary Professor at Macquarie University (Australia) and Gabriel Filippelli, Professor of Earth Sciences and Executive Director of the Indiana University Institute for Environmental Resilience (USA).

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Declaration of Interest

• Health

• Video

• The Conversation

• Hygiene

• Shoe

• Bacterium

• E.coli bacteria

• Pollution