A few lessons were buried in the rubble of the World Trade Center. Humans change the environment -- and build environments -- in ways that make them vulnerable to catastrophe.
Following the Sept. 11, 2001, attacks on the World Trade Center and the Pentagon, many experts have become more concerned that terrorists may maliciously spread biological agents such as anthrax or smallpox.
While petrochemical plants get the most attention, statistics from the Chemical Safety Board suggest that media overlook three quite common and widespread hazards: chlorine, ammonia, and propane