We are increasingly talking about the possible risks associated with the use of plastic containers to heat food in the microwave. A very widespread habit in daily life, chosen for convenience and speed, but which continues to raise many doubts. The underlying question is essentially: can heat promote the release of chemicals into food?
To clarify this point, the Swiss magazine K-Tipp sent 12 plastic food containers – including products also available in Italy such as those from IKEA – to a specialized laboratory.
Each container was subjected to in-depth analysis, looking for traces of 36 different potentially dangerous substances: from plasticizers such as phthalates to bisphenols A and F, known endocrine disruptors.
The method chosen was deliberately realistic. No standardized laboratory mixtures, the researchers filled each container with a deciliter of Barilla tomato sauce, then heated it for three minutes at 600 watts. The tomato, as we know, is particularly aggressive with materials and therefore represents one of the worst possible conditions for testing chemical migration.
The results
None of the 12 containers released measurable amounts of plasticizers (phthalates) or bisphenols A and F into the food. The latter are among the most monitored substances in the food sector: bisphenol A is known to interfere with the hormonal system, fertility and, according to the EFSA, to increase the risk of lung and autoimmune diseases.
The products tested include IKEA Pruta and IKEA 365+ containers, Emsa Clip & Close Eco and Emsa Clip & Close, Rotho Eco, Rotho Elements and Rotho Ela, as well as a range of Migros, Coop branded containers and the Crofton set from Aldi. All made of polypropylene (the code to look for on the bottom of the container is the number 5 inside the triangle, often accompanied by the acronym PP). And everyone, without exception, passed the test.
However, there is an interesting detail that emerged from the analysis. Before even heating the sauce, the lab had detected the presence of a plasticizer — acetyltributyl citrate (ATBC) — directly in the tomato sauce in the original bottle. The substance did not come from the containers tested, but most likely from the seal on the cap of the glass bottle, which migrated into the tomato during storage.
The good news is that heating in the microwave dramatically reduced this substance. The concentration went from 3 micrograms per kilogram in the cold sauce to an average of 0.4 micrograms in the hot sauce. In short, the plasticizer evaporates with heat. Chinese researchers in 2025 had reported potential negative effects of ATBC on the gut in the long term, but the amounts detected after heating were still minimal.
It must be said, however, that while the Swiss test excludes risks linked to chemical migration in the conditions analyzed, a study published in Ecotoxicology and Environmental Safety instead, it signals possible biological effects of heated plastic on the body, in particular on the intestinal microbiome.
Be careful of microplastics
The issue of microplastics remains open and deserves separate reflection.
A 2023 study conducted at the University of Nebraska analyzed, using highly sensitive methods, the ability of plastic containers to release micro- and nanoplastics into food. The results show that both heat and cold brittle plastic: microwaving is the worst condition, followed by freezing. Even at room temperature, however, a chemical process called hydrolysis slowly degrades the material over time.
Basically, a new polypropylene container doesn’t release harmful chemicals when heated, but over time — and with repeated use — the plastic wears, discolors, and absorbs odors to a much greater extent than glass or steel. A previous test by the magazine “Saldo” had already demonstrated this practical aspect.
The final message of this test is, however, more nuanced than a simple “plastic yes” or “plastic no”. Heating food in an intact, good quality and not old polypropylene container is not a proven source of chemical risk. However, if you want to minimize exposure to microplastics in the long term, or for greater attention to the environment, glass and steel remain the safest choice as well as being more long-lasting and less subject to aesthetic deterioration.
In the meantime, a handy tip: If your favorite plastic container is dull, discolored, or still smells like last week’s gravy, it’s time to think about a replacement.
