Isegoria

For the love of God, Wired pleads, stop microwaving plastic:

Microwaving delivers a triple whammy: heat, UV irradiation, and hydrolysis, a chemical reaction through which bonds are broken by water molecules. All of these can cause a container to crack and shed tiny bits of itself as microplastics, nanoplastics, and leachates, toxic chemical components of the plastic.

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Our kidneys remove waste, placing them on the front lines of exposure to contaminants. They are OK at filtering out the relatively larger microplastics, so we probably excrete a lot of those. But nanoplastics are small enough to slip across cell membranes and “make their way to places they shouldn’t,” Boland says.

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“Babies are at greater risk from those contaminants than full-grown people,” Hussain says. So to test how much plastic babies are exposed to, Hussain’s team chose three baby-food containers available at a local grocery store: two polypropylene jars labeled “microwave-safe” according to US Food and Drug Administration regulations, and one reusable food pouch made of an unknown plastic.

They replaced the original contents of each container with two different liquids: deionized water and acetic acid. Respectively, these simulate watery foods like yogurt and acidic foods like oranges.

They then followed FDA guidelines to simulate three everyday scenarios using all three containers: storing food at room temperature, storing it in the refrigerator, and leaving it out in a hot room. They also microwaved the two polypropylene jars containers for three minutes on high. Then, for each container, they freeze-dried the remaining liquid and extracted the particles left behind.

For both kinds of fluids and polypropylene containers, the most microplastics and nanoplastics — up to 4.2 million and 1.2 billion particles per square centimeter of plastic, respectively — were shed during microwaving, relative to the other storage conditions they tested.

In general, they found that hotter storage temperatures cause more plastic particles to leak into food. For example, one polypropylene container released over 400,000 more microplastics per square centimeter after being left in a hot room than after being stored in a refrigerator (which still caused nearly 50,000 microplastics and 11.5 million nanoplastics per square centimeter to shed into the stored fluid). “I got terrified seeing the amount of microplastics under the microscope,” Hussain says.

To test what these plastics do to our bodies once they’re consumed, the team bathed human embryonic kidney cells in the plastic roughage shed by the baby-food containers. (The team chose this kind of cell because kidneys have so much contact with ingested plastic.) After two days of exposure to concentrated microplastics and nanoplastics, about 75 percent of the kidney cells died—over three times as many as cells that spent two days in a much more diluted solution.

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