The habit of storing leftovers in plastic containers in the freezer and reheating them in a microwave may increase exposure to microplastics, experts have warned.
In an interview with the Daily Mail on Tuesday, British consumer group Which? recommended using glass or stainless steel containers instead of plastic for freezer storage. The reason: plastic hardens at sub-zero temperatures and develops microscopic cracks, releasing invisible particles in the process.
The American Chemical Society (ACS) journal Environmental Science & Technology has also published research showing that repeated freezing and heating can increase the release of microplastics from plastic containers.
The risk is compounded at the microwaving stage. Dr. Brian Helfand, a U.S. urologic oncologist, warned in an interview with the health outlet Parade that heating plastic containers can cause chemicals such as bisphenol A (BPA), phthalates and styrene to migrate into food.
Microwaves generate heat by rapidly vibrating water molecules, and microscopic particles can mix into food during this process. Helfand explained that the phenomenon is particularly pronounced when using old, scratched or damaged containers, or when heating high-fat foods at high temperatures.
Microplastics are plastic particles smaller than 5 millimeters, and they are now being detected throughout the human body, including in blood, lungs, placenta and brain tissue.
Researchers at the University of California, San Francisco School of Medicine have analyzed the possibility that microplastic exposure is linked to certain cancers, including colon and lung cancer. However, the long-term effects on the human body have not yet been clearly identified, and the World Health Organization (WHO) has only gone as far as reporting the existence of hundreds of endocrine-disrupting substances.
Experts say there is no need to discard all plastic containers immediately. The risk is relatively low for general uses such as refrigeration or storage of dry foods.
"There is no need to be overly anxious about intermittent exposure," Helfand said, while stressing that "cancer risk is heavily influenced by long-term repeated exposure, so it is important to consistently make small changes in daily life."
When reheating food in a microwave, the principle is to transfer it from plastic containers into glass or ceramic ones rather than using the plastic as is.
Even if a container is labeled "microwave-safe," the possibility of chemical leaching cannot be completely ruled out, so reheating delivery containers or single-use plastics should be avoided. If a cover is needed, paper towels or microwave-specific covers should be used instead of plastic wrap, and scratched or old containers should be replaced with new ones.
