The situation: It's time to bake something delicious—but when you pull out your trusty loaf pan (or muffin tin, or cast iron skillet) you see a few spots of rust forming inside.
What you're worried about: Consuming food that's made contact with rust. What if it's toxic? What about tetanus?! (You’re also eating tons of wood—check out these 31 foods containing sawdust.)
What will probably happen: Likely nothing. While tetanus is a potentially fatal infection of the nervous system, it's caused by bacteria (spores of the bacterium Clostridium tetani, to be specific), not by rust itself. The bacteria are most often found in soil and animal feces, according to the NIH—and it just so happens that the items we typically associate with tetanus (say, rusty nails) are usually found outside where they've been mingling with the bacteria (speaking of bacteria, this is what really happens when someone double dips). So if for some strange reason your bakeware has been exposed to those particular elements (and if you're not up to date on your tetanus vaccinations) it's probably better to replace the rusty item outright.
If your rusty cookware happens to be made of cast iron, most culinary authorities say it's completely salvageable. In fact, with a few simple tools and a little elbow grease, there are plenty of ways to thoroughly remove rust from cast iron (these 4 tricks will make your old pans shine like new again).
Experts at the University of Illinois at Urbana-Champaign agree that a little bit of rust on cookware isn't likely to harm you. (Even rust in drinking water isn't considered a health hazard.) But at end of the day, it may be best to play it safe—at least, that's the opinion of toxicologist James H. Woods, PhD, of the department of environmental and occupational health sciences at University of Washington. "I am not aware of any studies showing any significant health issues associated with eating food prepared in rusted cookware, but why take the risk?" he says. "I'd buy new cookware."