Microwaves and plastic containers - Cancer Myths - Microwaves & Plastic Containers

Microwaves and plastic containers

A widely circulated e-mail suggests that heating food in a microwave using plastic dishes or plastic wrap will increase the risk of developing cancer. There is some scientific evidence to suggest that substances used to manufacture plastic products may leach out of the container and into the food it holds, and that some of them may be carcinogenic (cancer-causing).

The Canadian Cancer Society is aware that this e-mail may be a source of concern for Canadians, so it is providing this information to explain what we know and how you can minimize any risk that may exist from using plastic when reheating food in your microwave.

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 manufactured to store the food and liquid that we eat and drink
Companies that make plastic containers for food storage use different substances and manufacture the containers differently than they would if they were making containers for other intended uses. Because of this, it is important to use plastic containers only as intended, particularly when storing food.

To ensure the safety of plastic containers sold with food or drinks in them, Health Canadaâ€™s Food Directorate does a pre-market evaluation on the new product to determine safety.

In Canada, plastic containers that do not contain food when sold, but are designed for this use, are not tested before they are brought to market and there are no guidelines to govern what substances are put in the plastic. However, the Consumer Product Safety Bureau of Health 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.

To ensure safe use of plastic containers or wrap that is in contact with food during reheating, Health Canada states that using plastic containers and wrap for anything other than their original purpose can cause health problems. It also recommends the following:

Do not use plastic bowls or wrap in the microwave unless they are labelled as microwave safe. (The Food and Drug Administration in the United States suggests that packaged food with labelling instructions for heating in the package or storage containers sold for use in microwave ovens are 2 examples of such containers.) There has been some concern that food may absorb some of the plasticiser 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. Plastic containers that release anything more than an insignificant amount of these substances are not approved for use in Canada.
If plastic containers are re-used as storage, let the food cool before storing, then refrigerate it immediately. Avoid visibly damaged, stained or unpleasant smelling plastics and containers.
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 migrate into the food.
For more information
Health Canada
American Cancer Society
United States Food and Drug Administration
Health Products and Food Program, Food Directorate
(for information about plastic containers sold with food in them)

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

Last modified on: 29 September 2008
2009 Canadian Cancer Society. All rights reserved.