Many people use something called “treated wood” when constructing things like backyard decks. It’s a preferred choice for many contractors because treated wood -- on which toxic chemicals like arsenic are used -- is long-lasting and resists decay. But it’s also very toxic. Most communities consider treated wood scraps and even saw dust as a household hazardous waste and refuse to accept it in regular trash pickups. If you have scrap treated wood, never burn it; that releases the toxins through emissions and ash. Instead of chemically treated wood, look for natural alternatives like cedar or recycled plastic composite decking.