By some measures, chemical plants like the sites of separate fatal explosions this week in Louisiana are among the safest manufacturing workplaces in America....[But] residents and emergency responders...[keep] wary eyes on the hundreds of facilities stretched along the Mississippi River...Because of the volatile nature of many of the products they make, explosions, chemical releases and other accidents are real threats...State and local officials have welcomed oil refineries, chemical plants and related industries, with their heavy capital investments and good-paying jobs. Louisiana is experiencing a boom in new plants and expansions..."This is an example of what it's like to live along a massive petrochemical corridor," said Marylee Orr, executive director of...Louisiana Environmental Action Network. "It poses a risk to the workers first and then to the community that lives right along the front line." [refers to Williams Companies, CF Industries, Westlake Chemical Corp.]