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Microwaves and plastic containers

You may be concerned that heating food in a microwave using plastic dishes or plastic wrap will increase your risk of developing cancer. Many different chemicals are involved in the manufacturing of plastic, and some of these may cause cancer. It is possible that these chemicals may leach out of the container and into the food it holds.

The Canadian Cancer Society is aware that this may be a concern for Canadians, so it is providing this information to explain what we know and how you can reduce any risk.

There are a number of different kinds of plastic containers:

  • some are designed for household products 
  • some are used to hold gardening supplies 
  • others are specifically made to store the food and liquid that we eat and drink 

Companies that make plastic containers for food storage use different substances and make the containers differently than when they make containers for other uses. Because of this, it's important to use plastic containers only as intended, particularly when storing food.

For plastic containers sold with food or drink in them, Health Canada's Food Directorate evaluates the safety of these products before they're sold.

Plastic containers that don't contain food when sold, but are designed for this use, are not tested by Health Canada and there are no guidelines on what substances can be used to make them. However, the Consumer Product Safety Bureau will investigate any concerns about the safety of this type of product and will ask manufacturers to remove any substances that pose a health risk.

There has been some concern that food may absorb some of the plasticizer used in plastic to make it more flexible - particularly at high temperatures when microwaving or when heating fatty or oily foods like cheese and meat. To ensure the safe use of containers or wrap that are in contact with food during re-heating, you can do the following:

  • Use glass, ceramic and plastic containers and plastic wrap that are labelled as microwave safe - for example packaged food with labelling instructions for heating in the package or storage containers sold for use in microwave ovens. Plastic containers that release anything more than a small amount of plasticizers are not approved for use in Canada. 
  • Never heat or store food in plastic containers that were not intended for food. One-time use containers, like margarine tubs, tend to warp or melt in the microwave, and this may allow more of the substances in plastic to go into the food. 
  • If you're using plastic containers for storage, let the food cool before storing, then refrigerate it immediately. Avoid plastics and containers that are visibly damaged, stained or have a bad smell.

For more information
Health Canada – Microwave Ovens and Food Safety
American Cancer Society – Microwaving Plastic
US Food and Drug Administration – Use Your Microwave Safely

Plastic containers sold with food in them
Health Canada – Health Products and Food Program, Food Directorate

Plastic containers designed for (but sold without) food in them
Call the Consumer Product Safety Bureau at (613) 954-0104.