That's an excellent and practical question! As a city dweller myself, I've often wondered the same thing when looking for a safe place to dispose of a cigarette. The short answer is: it depends entirely on the specific trash can's materials and design.
Most modern, purpose-built urban trash cans—especially those with designated cigarette disposal sections—are designed to withstand cigarette heat. They're typically made from metals like galvanized steel or aluminum, which have very high melting points (steel melts at around 1370°C/2500°F, while a cigarette burns at about 700-900°C/1292-1652°F at its hottest point). The real risk isn't melting the entire can, but rather damaging plastic components, liners, or causing a fire if proper precautions aren't taken.
Many cities now install specialized "cigarette butt receptacles" with self-extinguishing designs, sand or mineral wool fillers, and small, protected openings. These are engineered for this exact purpose. However, a standard plastic public bin is a different story. While it likely won't melt into a puddle from a single cigarette, it can certainly scorch, warp, or develop a hole, creating a fire hazard if other flammable materials are inside.
The key takeaway? Always look for a designated cigarette disposal unit. They're built for the job. If you don't see one, it's safest to carry a portable pocket ashtray. This protects the city's infrastructure and significantly reduces the risk of accidental fires. Responsible disposal keeps our cities cleaner and safer for everyone.