Eyes are sometimes raised when people are asked to remove their shoes before entering someone else’s home. Of course, it’s customary in some countries (not to mention maraes) to take off one’s shoes before entering. But it still riles some people. However, new research has shown that wearing shoes inside the house is not only gross, but a real health threat. Environmental chemists in Australia have spent a decade examining the indoor environment and the contaminants people are exposed to in their own homes. Their findings? It’s best to leave the filth that accumulates on the bottom of your shoes outside the house – for myriad reasons. Professor Mark Taylor is Victoria’s Chief Environmental Scientist at EPA Victoria. He explains why you should always be taking your shoes off before going inside.