Presidential hopeful George W. Bush today will unveil a plan for cleaning and redeveloping brownfields, or polluted industrial sites, as part of an effort to give himself a greener tint as he goes head to head with Al Gore. In a speech in suburban Pittsburgh, Bush plans to announce that he would direct the U.S. EPA to set more flexible standards for some brownfield cleanups, in order to encourage development on urban sites rather than sprawl onto farmland and other green areas. Gore and enviros have sharply criticized Bush’s environmental record as governor of Texas, which has a number of serious environmental problems, including the dirtiest air in the nation in the city of Houston.