Short-term exposure to smog is clearly linked to premature deaths, a National Academy of Sciences report has concluded. Some Bush administration officials have claimed that the link between ground-level ozone and health is, well, hazy: when the U.S. EPA was determining acceptable air standards for ozone last month, officials in the Office of Management and Budget claimed there was “considerable uncertainty” of a link. But the NAS declared that such arguments should be given “little or no weight,” and that agencies should assume that smog can kill when formulating future regulations.