Isis the Scientist has a post up from a couple days ago about an annoying "science for girls" video. The comments went off in another direction, to lab-appropriate clothing and making sure that you're protected from being doused with nasty chemicals or set on fire.
It drives me bonkers when I see folks wandering around outside with lab coats. In grad school, we wore lab coats when in the lab, and we had to take them off before we left. All labs (and my office, a former lab) had hooks for this purpose. It's simple: lab coats (and other personal protective equipment, or PPE to use environmental consulting jargon) protect you from nasties, but you need to take care that said nasties don't get spread around to a clean environment. I pass a well-known teaching hospital on my daily commute, and I always see doctors and others wandering about outside in their lab coats. Bad practice!
In environmental consulting, the closest analogue would be nitrile gloves. If you have the potential to be in contact with contaminated material, wear gloves. However, what often happens is that you're running around, doing a million things, and maybe the box of gloves got left somewhere inconvenient, and before you know it, you're driving around, drinking water, having a cigarette, all while wearing the gloves. This defeats the purpose.
Nitrile gloves cost like 3 cents a pair. Just like the strapping tape for a cooler or paper towels, the cost of gloves is infinitesimal compared to the overall job cost. Don't penny-pinch the small stuff (I complained about this practice ages ago). Change your gloves whenever you move on to another task, and always when you're going off-site, so you don't freak out the neighbors.