Watch out before you microwave your leftovers in a plastic container

For many people, plastic is an indispensable part of their kitchen. It's highly versatile, interacting with foods and beverages as a storing and serving material.

It's tempting to include it in an often-crucial stage of the eating process: microwaving. But is it OK to heat up plastics in the microwave, and what effect does this have on your health?

The evidence on whether plastic is safe to microwave is “not totally compelling,” said Dr. Joseph S. Alpert, a professor of medicine at the University of Arizona. 

When foods or beverages are microwaved in plastic containers, some of the substances and chemicals inside the plastic, known as nanoplastics, are shed into the food. These can present health risks, including a higher risk of cardiovascular disease and stroke, and hormonal, metabolic and reproductive changes, particularly for vulnerable groups like pregnant women or children.

The data is “skimpy” on the actual harm from plastics in food, Alpert said. He noted if there was a definite health risk, the U.S. Food and Drug Administration would issue a warning. 

All food contact materials must meet strict FDA safety standards before they are permitted, and several plastics dangerous to human health have been removed from the market. Still, “if you want to play it safe, microwave food in glass or ceramic containers that do not contain lead, and don’t microwave food in plastic containers,” Alpert said.

What type of plastic can I microwave?

Certain containers, labeled “microwave safe,” are specifically designed to withstand high microwave temperatures. However, this means the material is certified to not melt, warp or explode, not that it is entirely safe from a health perspective, and they still contain chemicals.

Can I prevent the ingestion of nanoplastics?

The heat in the microwave accelerates the release of the substances in plastic, but it isn’t the only way these chemicals wind up in your diet. Placing foods in plastic containers that are still hot, using containers for an prolonged period and exposing it repeatedly to the dishwasher can all lead to the release of chemicals. 

Choosing glass or ceramic containers is a safer option for those concerned.