Is It Really That Bad to Use Plastic in the Microwave?

You might want to re-think your packed lunch strategy.

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Photo by: Brett Stevens/Getty Images

Brett Stevens/Getty Images

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Most of us are aware that plastic and microwaves are a bad match. But despite that knowledge, we sometimes fall into the trap of, say, heating up our Tupperware-packed lunches we’ve brought to work in the office microwave.

If you really do a deep dive into the dangers of plastics in the kitchen, you probably would quit this bad habit cold turkey, but the truth is we're all strapped for time and are just looking for a safe way to heat our leftovers in the microwave in less than two minutes.

That's why we rounded up some quick guidance on how to microwave safely in a plastic world. It should take you not much longer to read than it takes to zap … um … whatever those leftovers you’re eating are.

What’s the problem with plastic, anyway?

The evidence is mounting that plastic food containers are bad for our health. The two key culprits are the man-made chemicals Phthalates and Bisphenol A (BPA), which are often added to plastic to help it keep its shape and pliability. Known as “endocrine disruptors,” these substances have been found to affect hormones, such as estrogen and testosterone, which can cause reproductive and other medical problems. They may be especially dangerous to children, potentially impeding normal growth and development, according to the Pediatric Environmental Health Specialty Units.

Wait, isn’t this stuff regulated?

Well, yes and no. The U.S. Food and Drug Administration says it’s on the job. But last July the American Academy of Pediatrics called for more stringent federal food safety requirements, noting that many of the chemicals added to foods and packaging was grandfathered in decades ago or designated “Generally Recognized as Safe” without undergoing an FDA approval process. “There are critical weaknesses in the current food additives regulatory process, which doesn’t do enough to ensure all chemicals added to foods are safe enough to be part of a family’s diet,” AAP Council on Environmental Health member Leonardo Trasande, MD, MPP, FAAP, said in the organization’s policy statement. The AAP specifically flagged the dangers of BPA and Phthalates.

OK, so what does that mean for microwaving?

Basically, heat can cause the BPA and Phthalates in plastics to leach into your food. That means – yeah, sorry – you should avoid microwaving food and beverages in plastic. Instead, transfer them into microwave-safe glass or ceramic containers. And those “microwave safe” plastic dome covers? The FDA says they’re OK, but, if you need to cover your food, it’s probably safest to use wax paper, parchment paper, a white paper towel or even a ceramic plate.

Are some plastics worse than others?

In general, steer clear of plastic with recycling codes 3 (phthalates), 6 (styrene) and 7 (bisphenols) except for those that are marked as “biobased” or “greenware,” the AAP cautions. The Environmental Working Group stresses that, when storing food, if you have to use plastic, you should avoid anything marked with recycling 7 and use 4 instead. “#1 and #2 are BPA-free, but some researchers do not recommend their reuse,” EWG notes. Meanwhile, Harvard Health advises that plastic takeout containers and grocery-food tubs (the kind used for margarine or yogurt) are generally not microwave-safe; prepackaged microwave food trays should not be reused; old, scratched or cracked containers may be especially apt to leach chemicals and should be tossed; and microwaving food in plastic bags is a big no-no.

Any other tips?

Washing plastic containers in the dishwasher can also prompt them to leach chemicals and should also be avoided. If you must wash plastics marked “dishwasher safe,” place them in the top rack, far from the heating element, Consumer Reports advises.

In sum, glass and "microwave-safe" ceramic dishware are your friends when microwaving food. Your enemy? One word: plastics.

*This article was written and/or reviewed by an independent registered dietitian nutritionist.

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