Yes. There are urban planter boxes made from materials chosen to minimize chemical leaching into soil, especially for edible gardening. The key is to avoid treating “won’t leach” as an absolute guarantee: all materials can release trace substances under some conditions, and soil pH, temperature, UV exposure, age, and fertilizer salts matter. The practical goal is to use inert, stable, food-contact-approved materials and to protect them with a suitable liner where needed.
Among the best low-leaching options are food-grade high-density polyethylene and polypropylene. These plastics are widely used for food storage and are generally stable, but choose products that are UV-stabilized for outdoor use and avoid unknown recycled plastics that may contain contaminants. Stainless steel, especially 304 or 316 grades, is another strong choice; 316 is more corrosion-resistant in coastal or salty environments. Powder-coated metal can work well if the coating is fully intact and free of chips, because exposed or lower-quality coatings may introduce risk. Lead-free glazed ceramic is good for small planters, but verify that the glaze is labeled lead-free and suitable for food gardening.
Materials to treat with caution include galvanized metal, which can release zinc, particularly in acidic soil; pressure-treated wood and old railroad ties, which may contain preservatives; recycled tires; flexible PVC; and paints or stains not intended for food-contact or soil-contact use. Untreated rot-resistant wood such as cedar or redwood is often considered a lower-risk natural option, but it is not completely inert and will eventually degrade.
If you want extra protection, use a food-grade high-density polyethylene liner or a fully cured, inert waterproof liner with drainage holes protected by geotextile, and leave a drain path so water does not stagnate. Avoid abrasive cleaning that scratches plastic or coating. For recycled-content products, ask for certification or test data for soil contact. When in doubt, grow leafy greens in lined beds or use containers made for edible gardening. So yes—urban planter boxes can be made from materials that greatly reduce leaching risk, but the best choice combines safe material, sound construction, drainage, and realistic maintenance.