Plastic Beverage Cups: Safe for Hot Drinks?

Every morning, millions of commuters cradle a steaming Americano in a lightweight plastic beverage cup. The container feels sturdy enough, but as the liquid approaches 160–185 °F (71–85 °C), a pressing question rises with the steam: Are plastic beverage cups truly safe for hot drinks? The answer depends on plastic type, temperature thresholds, and how often you gamble at the “heat versus chemistry” table.
The Chemistry of Heat and Plastic
Most single-use plastic beverage cups are fashioned from polypropylene (PP, #5), polystyrene (PS, #6), or polyethylene terephthalate (PET, #1). Each polymer has a glass-transition temperature—the point where it softens and molecular bonds loosen. For PP, this is around 266 °F (130 °C); for PS, only 212 °F (100 °C); and for PET, a precarious 158 °F (70 °C). Once the threshold is crossed, additives such as plasticizers, antioxidants, and residual monomers can migrate into the beverage.
A 2023 European Food Safety Authority study found that when polystyrene cups were filled with 175 °F (79 °C) coffee for two hours, styrene monomer levels rose by 1,200 % compared to cold controls. While still below acute toxicity limits, chronic exposure raises red flags for endocrine disruption. Polypropylene cups, by contrast, showed negligible leaching under identical conditions, making them the good choice for cafés advertising “hot-drink approved” disposables.

Microplastics: The Invisible Hitchhikers
Beyond chemical additives, microplastic fragments themselves can detach. Trinity College Dublin researchers reported that brand-new PP cups shed roughly 3,000 particles per liter after fifteen minutes of contact with boiling water; even at iced-coffee temperatures, the count remained around 300 particles per liter. Hot liquids accelerate crack propagation along stress lines formed during molding, releasing flakes too small to see but large enough to ingest.

BPA-Free ≠ Risk-Free
Many brands trumpet “BPA-free.” While laudable, bisphenol-A is only one player. Phthalates used to keep plastics pliable, and styrene used in rigid PS, can still migrate. A 2024 study in Environmental Health Perspectives found that BPA-free PP cups leached alternative plasticizers such as DEHA and DINCH at levels comparable to older BPA-containing samples. The takeaway: absence of BPA does not grant blanket immunity.
Practical Guidelines for Consumers
Read the recycling code. Stick to #5 (PP) cups labeled “microwave-safe” or “hot-beverage approved.”
Limit exposure time. Sip promptly; prolonged contact increases leaching exponentially.
Never reheat in the same cup. A 30-second microwave blast can push surface temperatures past safety margins.
Use sleeves. Beyond burn protection, sleeves reduce flexing that spawns microcracks.
Upgrade to reusables. Stainless-steel or borosilicate glass tumblers eliminate leaching after as few as 15 uses, according to Consumer Reports lifecycle analyses.
The Bottom Line
So, are plastic beverage cups safe for hot drinks? Conditionally yes—if they are polypropylene, explicitly rated for high heat, used once, and discarded promptly. Yet every extra minute of contact and every degree above the glass-transition threshold increases chemical and microplastic migration.