False – as long as they are labelled “microwave safe”. There was a widely circulated email warning about the dangers of microwaving food in plastic containers or plastic wrap. The message warned that can leach chemicals out of the plastic and into the food, especially foods with a high fat content like cheese and meats, causing cancer and reproductive problems.

There is some evidence to suggest that certain plasticizers (additives used to make plastic flexible) called phthalates, can leach out and cause cancer and reproductive problems in animals. But the effect isn't clear in humans. Phthalates are commonly found in soft plastics, like the kind meat is wrapped in, and in take out containers.

To ensure safe use of plastic containers or wrap in the microwave:

• Do not use plastic containers or wrap unless they are labelled “microwave safe”. Packaged foods with instructions for microwave heating in the container and storage containers sold for use in microwave ovens are two examples of safe containers. Plastic containers like margarine tubs, yogurt containers, take out containers, whipped topping bowls, and other one-time use containers are not considered safe.
• Do not let plastic wraps touch the food when heating. Leave one inch between the food and plastic wrap when heating in the microwave. Do not use thin plastic storage bags, plastic grocery bags or aluminum foil in the microwave.
• Remove food from the store wrap before thawing or reheating in the microwave, unless the manufacturer has indicated that it's meant for microwave use.