With spring in full bloom and warm weather here to stay (fingers crossed), many of us are seizing the opportunity to get outdoors. Getting outside after a long winter—not to mention being cooped up for two years of pandemic life—feels great. But spending more time outside could have one not-so-great side effect. Read on to find out what common habit could potentially bring harmful contaminants into your home, and what to do to keep you and your family healthy.
According to a 2009 article in the journal Environmental Science & Technology, roughly one-third of the dirt, dust, and household toxins that accumulate in your home are brought in from the outdoors. This buildup of outdoor filth doesn’t appear on its own. Rather, it’s tracked in by people wearing shoes indoors.
A study published in the Journal of Cleaning Science examined the germs collected on footwear and found harmful bacteria on 96 percent of shoes. The researchers detected E. coli on 27 percent of shoe bottoms, plus traces of fecal bacteria and C. diff. Alarmingly, over 90 percent of this bacteria gets transferred from shoe bottoms to the floors in your home.
Walking around your home with shoes on causes bigger problems than just needing to vacuum more often.”Wearing shoes indoors tracks in pesticides used outdoors, chemicals associated with pavement, and bacteria, among other things,” explains Tasha Stoiber, PhD, a senior scientist with the Environmental Working Group (EWG).
The health risks of wearing shoes inside are serious. Asphalt pavement residue found on shoe bottoms has been linked to cancer, and certain chemicals used in lawn care are known hormone disruptors. In addition, your shoes can carry in traces of potentially toxic metals (including cadmium, arsenic, and neurotoxic lead), which are odorless and colorless. Research has shown a significant correlation between the lead found inside your house and the lead in yard soil that gets tramped in on your shoes.
“[Common household toxins] include flame retardants, PFAS chemicals, phthalates, phenols, and fragrance chemicals,” warns Stoiber. She explains that these chemicals tend to build up in household dust, where they can be inhaled and ingested—especially by small children who spend ample time on the floor. These chemicals can also be brought in on the soles of your shoes.
For all those reasons, Stoiber says, “We recommend leaving your shoes at the door and not wearing them inside.”
While chances are you won’t experience any detrimental health effects of wearing shoes inside right away, the ingestion of household toxins may cause several symptoms over time, including irritation of eyes, nose, and throat, headaches, dizziness, fatigue, and trouble breathing.
“The health hazards linked to [toxin] exposures will depend on the specific chemicals detected in the home,” says Stoiber. “For example, PFAS chemicals, flame retardants, phthalates, and volatile organic compounds (VOCs) are associated with many health effects.” According to the EWG, the toxins Stoiber lists can cause cancer, harm your immune system, lead to respiratory problems, damage your liver and kidneys, increase cholesterol, and disrupt thyroid function.
And shoe bottoms are capable of tracking more than dangerous chemicals into your home. A 2016 study published in the Journal of Applied Microbiology found that they can carry infectious diseases and microbiological pathogens, especially among health care, community, and animal workers.
While exposure to some amount of indoor dirt and bacteria can be good for you, the evidence is clear: Wearing shoes inside is hazardous to your health.
To help decontaminate the air inside your home, Stoiber and the EWG suggest vacuuming with a machine that includes a high-efficiency particulate absorbing (HEPA) filter, regularly dusting your home with a damp microfiber cloth, and using a high-quality filter in your HVAC system.
Of course, to prevent potentially harmful chemicals and germs from entering your home in the first place, the best thing to do is get in the habit of kicking your shoes off before you kick back at home.