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December 3, 2004

Cooking with Plastics

Rolf Halden, PhD, PE

Rolf Halden, PhD, PE

Many people are concerned about the use of plastics for preparing and eating foods and beverages. Recently, Rolf Halden, PhD, PE, assistant professor in the Department of Environmental Health Sciences and the Center for Water and Health at the Johns Hopkins Bloomberg School of Public Health set the record straight about a hoax email warnings about the exposure to dioxins from freezing plastic bottles. The Office of Communications and Public Affairs sat down with Dr. Halden again to discuss the public health risks posed by plastic products.

Question: We are surrounded by plastic products and many people use them for cooking and preparing foods every day. Is there a concern with using these products?

Answer: In general, whenever food comes in contact with materials that are not inert there is a chance of chemical transfer and contamination. We are primarily concerned about plasticizers such as the various phthalates, acetyltributylcitrate and dioctyladipate, all of which are added to plastics to make the products flexible and less brittle. The concern is that if you heat up plastic food containers, utensils or plastic wrap, some of these chemicals could be released into food or beverage.

Question: How much of these chemicals get into our food and is it harmful?

Answer: That’s a difficult question and the best answer I can give is: it depends. Several European studies found that many plasticizers migrated from plastic containers and wraps into foods as they were heated in microwave ovens. Some of the chemicals were absorbed in high quantities (several hundreds of milligrams per kilogram food). The amount of chemical absorbed by the food depended on the temperature of the container and food, the duration of the heating, the type of plastic used and its initial plasticizer content, as well as the type of food being heated. As a general rule, the fattier the food, the more of the chemicals potentially can be absorbed and retained by it. More research should be done in this area.

Question: What is the risk from exposure to these chemicals?

Answer: For example, phthalates are environmental contaminants that can exhibit hormone-like behavior by acting as endocrine disruptors in humans and animals. These “synthetic hormones” may pose a special risk to susceptible populations such as children, who are more vulnerable because they are still developing. But again, it’s not clear how much exposure to these chemicals is occurring. Potential adverse heath outcomes also are dependent on a person’s individual susceptibility.

Question: Should people be concerned about dioxins in plastic food containers more so than plasticizers you mentioned?

Answer: Plastics typically do not contain dioxins. However, dioxins can be formed in the environment from the incineration of waste, particularly the incineration of hospital waste, which contains a great deal of polyvinyl chloride plastics and aromatic compounds that can serve as dioxin precursors.

When dioxins are sent into the atmosphere they become attached to particles and eventually fall back to earth. Then they bind to, or are taken up, by fish and other animals, where they get concentrated and stored in fat before eventually ending up on our lunch and dinner plates. People are exposed to them mostly from eating meat and fish rich in fat.

Question: A number of readers contacted the Bloomberg School about the risk of warming plastic baby bottles or cooking with plastic bags. Do you have any advice for them?

Answer: The first thing is to use common sense and follow the manufacturer’s directions. Only utilize plastic containers, wraps, bags and utensils for their intended purpose. For example, grocery bags are manufactured to transport food and not to serve as cooking aids. The U.S. Department of Agriculture Food Safety Inspection Service (FSIS) has some helpful guidelines for cooking with plastics in microwave ovens.

If you want to minimize exposure to chemicals from plastics as much as possible during any type of cooking, use inert containers, such as heat-resistant glass, ceramics and stainless steel.

Question: Is it better to use a paper towel rather than plastic wrap to keep food from spattering in the microwave?

Answer: If you cover your food with a paper towel, the FSIS recommends using a plain “white paper towel” that does not contain inks or dyes. You can read their recommendations at the FSIS website. Critical readers may argue that white paper could be chlorine bleached and therefore potentially may contain dioxins. You see, there really is no way to completely avoid contact with ubiquitous toxic chemicals. The art is to avoid unnecessary exposures as much as possible by applying a healthy portion of common sense before sitting down and enjoying a meal.

Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Lowe at 410-955-6878 or paffairs@jhsph.edu.