Are Takeout Soup Containers Safe? Plastic, Foam and Paper

What are takeout soup containers made of?

Soup is the hardest test a takeout container faces: it arrives close to boiling, it is mostly water with some fat and acid, and it sits in the container for the whole ride home. Four kinds of packaging do most of the work. Read the resin code on the base or lid; the lid is often a different plastic from the cup.

Do takeout soup containers release microplastics?

In laboratory tests that resemble soup, yes, and the amount depends heavily on the material. The cleanest comparison comes from Hu and colleagues, who treated polypropylene, polyethylene and expanded polystyrene take-out containers with hot water and identified the released particles by Raman spectroscopy. On average they found 19,000 particles per liter from polypropylene, 101,000 from polyethylene and 2.82 million from foam. Particles ranged from 0.8 to 38 µm, and more than 96% were under 10 µm. The paper’s abstract attributes release partly to polymer chains relaxing when warm and partly to defects from manufacturing.

That is why foam sits at the bottom of the table. Our foam takeout container guide covers the polystyrene evidence, including styrene migration, in more depth.

Is it safe to microwave soup in the plastic deli container?

It is the step we would drop first. Hussain and colleagues at the University of Nebraska tested two polypropylene baby-food containers and a polyethylene pouch with water and 3% acetic acid, which stand in for watery and acidic foods. Microwaving caused the highest release of any scenario they tried, including months of refrigeration or room-temperature storage. Some containers released up to 4.22 million microplastics and 2.11 billion nanoplastics from each square centimeter of plastic within three minutes of microwave heating.

Keep the conditions in view. These were baby-food containers, not soup tubs; the count is per square centimeter, not per bowl; and the simulants were water and dilute acid, not broth with fat. The team also exposed human embryonic kidney cells to extracted particles: at 1,000 µg/mL, 76.7% and 77.2% of cells died after 48 and 72 hours. That is a very high laboratory concentration in a dish, not evidence of harm from one reheated lunch. Our microwaving plastic containers guide covers the full study and later evidence, and what “microwave safe” actually means explains why the label is about the container surviving, not about particles.

Are paper soup cups better than plastic?

Not automatically. A paper soup cup holds liquid because of a thin plastic layer on the inside. In Ranjan and colleagues’ study, the lining of the tested paper cups was mostly polyethylene, and 100 mL of water at 85 to 90°C left for 15 minutes held about 25,000 micron-sized particles by fluorescence microscopy. Zangmeister and colleagues at NIST found that LDPE-lined hot beverage cups released more than a trillion nanoparticles per liter, with mean particle diameters of 30 to 80 nm, and that release depended on how hot the water was. The NIST summary says the cups were exposed to 100°C water for 20 minutes. Food-grade nylon released seven times more than the cups.

Compostable cups swap polyethylene for PLA, a plant-derived polyester. In a 2026 comparison, Shi and colleagues found PLA-lined paper cups released about 11.6 µg of particles per liter of hot water against 0.9 µg/L from polyethylene-lined cups, roughly twelve times more by mass. Earlier studies have disagreed on which lining releases more; our compostable cup guide lays out both sides. The drink-cup research is collected in microplastics in coffee cups.

No study we found tested paper soup cups, foam and polypropylene side by side, so the evidence cannot rank a paper cup against a tub. None of these studies used soup; all used hot water. Treat every one of these as a way to carry soup, not as cookware.

How close are these tests to a real bowl of soup?

Closer than many microplastic studies, but not identical. Each test above changed one thing at a time, and the results are reported in different units: particles per liter, particles per square centimeter, particle mass per liter. They cannot be lined up into a single ranking, and you should not multiply any of them by your soup order.

Two features of soup are not covered at all: fat, which can draw some substances out of plastics more than water does, and the long ride home with steam condensing on a lid and dripping back in. We found no study that tested either for takeout soup containers. That is an honest gap, not a reason to assume the worst.

Why heat and time are the variables to watch

Across these studies, temperature is the lever that keeps coming up. Zangmeister’s team found release depended on the starting water temperature for every material they tested. Hu’s group linked release to polymer chains loosening when warm. Ranjan used water at 85 to 90°C, and freshly ladled soup can be at least that hot.

Soup is also meant to stay hot. USDA guidance is to keep cooked food at 140°F (60°C) or warmer until it is eaten or chilled, so a well-run order should still be hot when it reaches your door. You cannot change the temperature at which a kitchen serves soup, but you can control how long it stays in the container once it reaches you, and whether it ever goes back into the heat inside that container. Those two choices line up with the conditions that raised release in the studies: longer hot contact and microwave heating.

Is it the container or the soup?

Both can carry particles, and the container is the part you control. The FDA says microplastics in food come primarily from the environment where foods are grown or raised. Ingredients such as salt and seafood have been reported to contain microplastics, and a restaurant kitchen uses plastic tools, wraps and storage tubs before your soup is ever ladled out. Decanting at home does not touch any of that. It removes the one contact step that is hottest, longest and entirely in your hands.

Use the App

Which takeout containers are piling up in your kitchen?

Scan the tub, cup or lid. The app reads the declared material or resin code, tells you whether it is polypropylene, polystyrene foam or a lined paper cup, and flags the ones not to microwave.

What to do with takeout soup, step by step

1. On arrival, take the lid off. If you are eating now, pour the soup into a ceramic or glass bowl. It also cools faster in a wide bowl.
2. If it came in foam, move it out first. Foam had the highest particle counts and is not a container to keep hot food in.
3. To reheat, use a pot. USDA advises reheating sauces, soups and gravies by bringing them to a rolling boil, and leftovers in general to 165°F.
4. If you use the microwave, use a glass or ceramic bowl, which is also what USDA recommends: cover it with a microwave-safe cover, vent it, stir, and check the temperature in several places.
5. Store leftovers in glass. USDA says to divide a large batch into shallow containers so it cools quickly, refrigerate within two hours, and eat within three to four days.
6. Reuse tubs for cold things only, such as dry goods or craft supplies, and retire any that are scratched, cloudy or warped.

If you order soup often, ask whether the restaurant will fill your own insulated steel container. Policies vary, and some places will say no for hygiene reasons. Ordering from places that use polypropylene or paper rather than foam is the simpler win. For noodle cups and instant soups, see do cup noodles have microplastics.

What about soup containers from the grocery store?

Refrigerated soups in plastic tubs face a milder trip than takeout, because they are filled and sold cold. The risk point is the same: what you do at home. Heat the soup in a pot or a glass bowl rather than in its tub, even if the label shows a microwave symbol. Hussain’s storage results suggest long refrigeration also releases some particles, though microwaving released the most. Our plastic containers guide covers storage choices.

Can you freeze soup in takeout containers?

Cold is the gentle end of the range, so freezing is a lower-concern use of a polypropylene tub than heating. The studies we reviewed did not test freezing, and Hussain’s results show that even long cold storage is not zero release. The bigger issue is what happens next: frozen soup in a tub tempts you to microwave it in that tub. If you freeze soup in deli containers, run warm water over the outside to loosen the block and tip it into a pot, which USDA notes is a safe way to reheat frozen soup without thawing it first. For batch cooking, wide-mouth glass jars or glass containers with room left at the top for expansion avoid the question entirely.

What the evidence does not establish

• A particle count for a real bowl of takeout soup. Every study used water or simple simulants.
• A ranking across studies. Different units, methods and size cut-offs make cross-study comparisons misleading.
• A health effect from takeout containers. The cell result used a very high concentration in a dish. The FDA says current evidence does not show that levels of microplastics or nanoplastics detected in foods pose a risk to human health, and that there is not sufficient scientific evidence to show that particles from plastic food packaging migrate into foods and beverages.
• That “microwave safe” or “compostable” means particle-free. Neither label is a release test.

The FDA’s view and these laboratory studies are not in direct conflict: the studies show release under defined lab conditions, while the agency is judging whether that translates to measured risk in real food. Pouring soup into a bowl is a reasonable step either way.