A lot of people just pop food in the microwave in any old plastic container. It turns out that if you heat the wrong kind of container in the microwave, the plastic will leach into the food.
Diane Van with the U.S. Department of Agriculture said different plastics are made to withstand various temperatures, and if you heat a low-temperature plastic container or pour boiling liquid or soup into it, the plastic will melt or change.
The rule of thumb is to check the label or packaging, Van said. If it's made to be heated, it will be clearly marked and refer to the microwave on the packaging. If it's not labeled, don't heat it. If you heat a plastic container in the microwave and it has changed shape or texture, do not eat the food you put in it.
When it comes to plastic wrap, read the box. Most packaging says that when you use it in the microwave, the plastic wrap should be one inch away from the food. Make sure you vent it so the hot plastic doesn't stick to the food.
And watch out for the plastic containers you buy in the store. Unless they clearly indicate that they're microwave safe, do not heat them. Same goes for zipper bags. They should stay out of the microwave.
A recent study also found that BPA, a chemical found in plastics and aluminum cans, may raise the risk of asthma and other health issues. Many companies began removing BPAs from their products.