Your concern about lead in old urban soil is very valid and shows good awareness. Historical use of lead-based paint and leaded gasoline has left a legacy in many city soils. When it comes to new urban planter boxes, the risk is significantly lower, but vigilance is still key.
The primary source of lead contamination is the existing native soil. Brand-new, commercially purchased soil mixes or compost used to fill planter boxes are typically screened and safe. The real concern arises if the new boxes are placed directly on, or filled with, contaminated native soil. To ensure safety, follow these steps: First, use a reliable soil test kit or send a sample to a lab to check the native ground where boxes will sit. Second, build your planter boxes with a solid barrier—like landscape fabric—at the bottom to separate the fresh soil from the old ground. Third, always fill them with certified clean soil from a trusted source.
For added safety, opt for raised planter boxes with their own built-in bottoms. Growing fruiting crops (like tomatoes or beans) is generally lower risk than root vegetables (like carrots or potatoes) if any uncertainty remains. Washing all produce thoroughly and practicing good hygiene—like washing hands after gardening—further minimizes any potential exposure.
By taking these proactive measures, you can confidently enjoy the benefits of urban gardening in new planter boxes with greatly reduced concern about lead.