While you’ve probably been told at some point that it’s not a great idea to heat food in plastic, it’s understandable to question whether the risks are really worth worrying about—especially when you’re standing in front of the microwave with a plastic container in hand. So, can you microwave plastic or is the concern overblown?
It’s worth noting that research into the effects of plastic and microplastics on our health is still ongoing. That means it’s difficult to say with certainty what might happen if you occasionally microwave food in plastic containers.
Still, toxicologists say there’s enough evidence to suggest you should avoid microwaving plastic as much as possible. So, what’s the concern, and what actually happens when plastic is microwaved? Experts explain.
What are microplastics?
Microplastics are plastic particles less than five millimetres in size. They’re often so tiny that they’re invisible to the naked eye, explains toxicologist Dr Kelly Johnson-Arbor.
Unfortunately, microplastics have been detected just about everywhere—including in the air, food, water, and even in our bodies. “The presence of microplastics in the human body has raised concern about their potential to cause unwanted health effects, including inflammation, cancer and reproductive harm,” says Dr Johnson-Arbor. While it’s impossible to avoid them entirely and more research is needed, it’s a good idea to reduce your exposure where you can.
What happens when you microwave plastic?
There are a few things that can happen when you heat plastic in the microwave. One concern involves additives commonly found in plastics—bisphenol A (BPA) and phthalates, says associate professor of pharmacology and toxicology Jamie Alan. BPA is used to make hard, clear plastics, while phthalates are added to soften plastic. Both are considered hormone disruptors, as they can interfere with oestrogen and testosterone in the body, Alan explains.
Phthalates are often present in food storage containers, which means small amounts may leach out when heated, Alan says. While many companies have phased out BPA, the Environmental Working Group (EWG) notes that it’s still approved for use in food packaging.
But even plastics without phthalates or BPA may release microplastics when heated, Alan adds. “Some studies suggest that microwaving food in plastic containers carries a higher risk of microplastic release—and human exposure—than simply storing food in them at room temperature or in the fridge,” says Dr Johnson-Arbor.
One 2023 study published in Environmental Science & Technology found that microwaving plastic food containers released more than two billion nanoplastics and four million microplastics per square centimetre of plastic.
What can microplastics do to your health?
That’s still being investigated. “We aren’t totally sure,” says Alan, but she adds that the total amount of microplastics you’re exposed to over time likely affects your long-term health risk.
“Microplastics have been found throughout the human body, including in our blood, lungs and hair, which has led to concern among scientists,” Dr Johnson-Arbor says. “Chronic exposure may be associated with effects like changes to gut health, endocrine disruption and impacts on immune function.”
A recent study of post-mortem brain tissue, published in Nature Medicine, found that people diagnosed with dementia had up to 10 times more microplastics in their brains than those without the disease. While this doesn’t prove causation, it highlights a potential link.
“We still don’t fully understand how microplastics affect human health,” Dr Johnson-Arbor says. “More research is needed.”
What should you do instead of microwaving plastic?
Experts recommend avoiding plastic containers when reheating food. Instead, try:
- Heating food in glass containers
- Transferring leftovers to a non-plastic plate or bowl before reheating
- Warming food on the stovetop or in the oven
Other simple ways to avoid microplastics
Microplastics are found almost everywhere in the environment, making them tricky to avoid entirely, says Dr Johnson-Arbor. But there are practical ways to lower your day-to-day exposure:
- Swap plastic water bottles for better alternatives. Stainless steel, ceramic and glass are safer picks, Dr Johnson-Arbor says.
- Cut back on canned food. One scientific analysis pointed out that some cans are lined with BPA-containing plastic coatings. Choose products labelled BPA-free when possible.
- Eat fewer processed foods. One study found chicken nuggets had 30 times more microplastics per gram than fresh chicken breast.
- Use glass containers for food storage. It’s a simple way to prevent plastics from leaching into your meals.
- Install a water filter. Look for filters designed to reduce microplastic content in drinking water, says Alan.
The bottom line: Should you microwave plastic?
It’s tough to completely eliminate microplastics from your life—but microwaving plastic just adds to your exposure. “I’d avoid heating plastic wherever possible,” says Alan.
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