If I were choosing urban outdoor furniture for a spot with strong sun and plenty of city pollution, I would not look for one miracle material. I would look for a smart combination of materials that can handle UV, soot, exhaust grime, bird droppings, acid rain, and regular cleaning without rusting, fading, or looking tired after a year. My short list would be powder-coated aluminum, 316 marine-grade stainless steel, teak or another dense hardwood, and UV-stabilized HDPE or recycled plastic. For cushions and slings, I would use solution-dyed acrylic or a good PVC-coated polyester.
Powder-coated aluminum is probably the best all-round choice for frames, chairs, and tables in a city. Aluminum does not rust like steel, and a quality powder coat gives it a tough, UV-resistant skin that stands up to sun and pollution. It is lightweight, which matters if furniture needs to be moved for cleaning or events. The key is to buy a reputable powder-coated finish, not a cheap paint job. Chips should be touched up quickly, because once moisture and pollution get under the coating, the finish can degrade. I would also avoid very thin tubular frames that can dent easily in busy public spaces.
For high-traffic urban settings, 316 marine-grade stainless steel is worth the extra cost. Grade 304 is common, but 316 is better where there is road salt, coastal air, or heavy pollution. Stainless steel is strong, easy to wipe down, and does not need much more than mild soap and water. The catch is that even stainless steel can look dull or develop surface staining if city grime sits on it for months, so it needs regular rinsing. It is also heavier and more expensive, so I would use it for benches, table bases, and handrails rather than every chair.
Teak is still a great choice when you want warmth and a more human feel in a plaza, courtyard, or rooftop garden. Good teak has natural oils and dense grain that help it resist sun and moisture. It can be left to weather to a silver-gray, or oiled to keep its golden color. In polluted cities, teak will collect soot and grime, so a gentle wash with mild soap is important. I would avoid untreated softwood, because it can warp, crack, and grow mildew quickly. If teak is too expensive, other dense, certified hardwoods can work, but they need a proven outdoor finish.
UV-stabilized HDPE and quality recycled plastic are excellent low-maintenance options for urban seating, benches, and picnic tables. They do not rust, they are not attractive to termites, and they can be washed with soap and water. The important word is UV-stabilized. Cheap plastic will chalk, fade, and become brittle in the sun. Good HDPE keeps its color much longer and is often made from recycled material, which is a plus. It may not feel as premium as teak or metal, but for busy public spaces it is practical and forgiving.
Concrete and stone can work well for table tops, benches, and planters, but they are heavy and porous unless sealed. In a polluted city, porous surfaces can hold grime, so I would choose a tight, sealed finish and plan for regular cleaning. For cushions, I would choose quick-dry foam and solution-dyed acrylic fabric, and I would bring cushions inside or cover them when not in use.
The materials I would avoid are mild steel with poor coating, untreated softwood, cheap resin furniture, and low-grade outdoor fabric. They may look good on day one, but sun and city pollution tend to expose them fast. My practical pick? Powder-coated aluminum frames, 316 stainless steel where strength matters, teak for warmth, and UV-stabilized HDPE for easy-care seating. Add a simple maintenance routine, and that mix will handle both sun exposure and city pollution far better than any single material.