Alcoa, a company that makes aluminum panels for the construction industry, recently announced a new coating with the overwrought brand name Reyobond with EcoClean. When applied to aluminum panels, the titanium dioxide coating interacts with sunlight to break down the smog-causing compound nitrogen oxide into an innocuous substance that washes off the building in a rain. Alcoa claims that 10,000 square feet of coated aluminum would have the air-cleaning effects of 80 trees.