Do styrofoam takeout containers leach styrene into hot food?

What's actually in it

Styrene is the chemical building block of polystyrene, the material used in foam takeout containers, disposable cups, and deli trays. Small amounts of unreacted styrene stay trapped in the foam after manufacturing. When hot soup, coffee, or greasy food sits in these containers, the heat pulls styrene out and into whatever you're eating or drinking.

The International Agency for Research on Cancer classifies styrene as a "possible human carcinogen." It can also irritate the nervous system and affect your liver.

What the research says

A 2026 review in Food Chem examined how styrene migrates from food-contact materials into food. The researchers looked at different types of polystyrene products and measured how much styrene ends up in what you eat.

Temperature was the biggest factor. Hot foods pulled out far more styrene than cold ones. A hot bowl of soup in a foam container can absorb several times more styrene than a cold salad in the same container.

Fat content mattered too. Oily and fatty foods dissolved more styrene because styrene is fat-soluble. Think fried rice, buttery soups, or anything with cheese. Acidic foods like tomato sauce also increased migration.

Time was the third factor. The longer food sat in the container, the more styrene it absorbed. Leftovers stored overnight in foam containers had the highest levels.