Other Chemical Hazards [1]
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. All of these are only lightly protected and vulnerable to terrorists with basic knowledge and primitive weapons. Chlorine is commonly used in large quantities as a disinfectant in the drinking water and sewage plants of most large and mid-size cities. A tank car of chlorine on a siding or in transit could create a lethal plume miles long that could kill tens of thousands of people.
Ammonia is a highly toxic gas used in large quantities in various forms as an agricultural fertilizer and industrial refrigerant. It is often pressurized, making it more dangerous.
Propane, which can be flammable and explosive, is used widely in residential, industrial, and agricultural settings, and large amounts of pressurized propane are commonly present at wholesale and even retail distribution points, as well as on the transport network.
Chlorine, ammonia, and propane are often present in large amounts near densely populated areas. Roughly half of all hazmat incidents are actually transportation accidents -- a reminder of how the spread-out and undefended rail and road network offers special vulnerability to terrorists.