That’s a really thoughtful question, and I’m glad you’re looking out for your skin. The short answer is: it depends on the bench and where it’s located. Many public street benches, especially those made of wood, are treated with preservatives like copper-based compounds (e.g., alkaline copper quat or copper azole) to prevent rot, insect damage, and weather wear. These chemicals are generally considered safe for incidental contact, but they can sometimes cause mild irritation for people with sensitive skin or allergies, especially if the bench is wet or has visible residue.
Metal and plastic benches are typically less likely to cause skin issues because they don’t usually require chemical treatments. However, metal benches might be painted with finishes that could contain volatile organic compounds (VOCs) during the first few days after painting, but once fully cured, they’re usually harmless. Concrete benches are generally inert and safe.
If you’re worried about irritation, here’s a practical tip: avoid sitting on wooden benches that look freshly treated (you might notice a strong chemical smell or visible patches) or have moisture beading on them, as the chemicals can leach out more when wet. Wearing long pants or placing a light blanket down can be an easy barrier. In my experience, most city parks and public spaces use treated lumber that meets safety standards, but if you have very sensitive skin or a known contact allergy (like to metals or certain wood preservatives), it’s best to choose metal or stone seating when possible.
To be extra cautious, you could also check with your local parks department about the specific treatments they use—most are happy to share that information. Remember, casual sitting on a dry bench is unlikely to cause a problem, but for prolonged or direct skin contact, a little awareness goes a long way.