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Should you heat up plastic in the microwave?

Tasty, tasty Thai takeout often comes in plastic containers, but should you pop the tray in the microwave the next day to reheat your leftovers, or should you transfer it to a glass bowl instead?

A study from NYU Langone Medical Center recently published in the medical journal Hypertension says there’s a correlation between two chemical substitutes and an increased risk for high blood pressure and diabetes in children. The two substitute compounds, known as phthalates, are used in place of known carcinogen DEHP, and are designed to strengthen plastic wrap and processed food containers, as well as some soaps and cosmetics. “Heating enhances contamination,” Dr. Leonardo Transande, who authored the study, told The New York Daily News.

“The FDA does regulate the plastics that come in contact with food, and the most important take-home message is to read the label on the package or the container,” Dr. Natalie Azar, NBC News medical director, told Today. Plastics that are labeled “microwave safe” are fine to heat up, she says, but if the containers have the recycling numbers 3, 6, and 7, then they contain those chemicals mentioned in the study.

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This also means that you don’t want to put those containers in the dishwasher, which also heats up plastic, and you should throw away scratched plastic containers, as they can leech chemicals.

If all this sounds familiar, it’s because something similar happened with another chemical found in plastic, BPA. Some research suggests chemicals used to replace it may cause the same kind of hormone disruption as BPA was found to cause.

And while Azar says the NYU study “was absolutely not a cause-and-effect finding,” meaning the study showed a correlation but not necessarily causation, Dr. Transande says there needs to be a better way to regulate chemicals. “What we need here is a reform that tests chemicals proactively before they’re used on the open market,” he tells Time.