Coniferous forests may produce more smog components than traffic does, calculations suggestMaybe Ronald Reagan was right after all about trees being big polluters. A new study suggests the Scotch pine and other northern evergreens may emit more nitrogen oxides -- key components of smog -- than all the cars and industrial plants on the planet.It has been known for years that some plants emit small amounts of nitrogen oxides. Now, a team of Finnish and U.S. researchers has found that Scotch pine needles increase those emissions substantially when they are exposed to ultraviolet radiation from the sun. This led the...