Scientists have found that even "microwave-safe" plastic should not be heated

Scientists from the University of Nebraska at Lincoln (USA) figured outthat micro- and nanoplastics are released when heating plastic food containers in a microwave oven. To do this, they experimented with heating baby food containers made from polypropylene and polyethylene, materials that the US FDA certified as safe to use.

To do this, different liquids were poured into containers and heated for 3 minutes at 1000 W in a household microwave oven. After that, the liquid was analyzed for the presence of microplastics (particles larger than a thousandth of a millimeter in diameter) and nanoplastics (smaller particles).

The number of particles varied between tests, but on average, after 3 minutes of heating, each square centimeter of plastic emitted 4.22 million micro- and 2.11 billion nanoparticles. Most of the particles were released when water and dairy products were heated in the microwave, but additional tests showed that the particles stood out even when food and drinks were stored in such plastic in the refrigerator and at room temperature - albeit in much smaller volumes.

To test the potential danger, the scientists exposed lab-grown fetal kidney cells to plastic particles that had accumulated in containers over several days. At the maximum concentration in 72 hours, microplastics destroyed 77% of kidney cells.

Although the kidneys are unlikely to encounter such concentrations of plastic directly, this makes it possible to understand the toxicity of micro- and nanoplastics - especially for a developing organism.

Scientists are going to continue research to find out what harm plastic particles can do to the body. The authors also emphasize the need to find or develop polymers that will release fewer particles when heated.