Ten months ago, government safety officials warned that more than half of the nation's 60,000 pressurized rail tank cars did not meet industry standards, and they raised questions about the safety of the rest of the fleet as well.
Their worry, that the steel tanks could rupture too easily in an accident, proved prophetic.
On Thursday, a derailment in South Carolina caused a catastrophic release of chlorine: Nine people died, 58 were hospitalized and hundreds more sought treatment. Thousands of people within a mile of the accident were driven from their homes.
And last summer, a derailment in Texas caused a steel tank car to break open, spewing clouds of poisonous chlorine gas that killed three people.
The exact causes of the accidents are still under investigation. But the devastation they have wrought shows why tank cars have become an increasing concern not just to safety investigators but also to domestic security officials worried that terrorists could turn tank cars into lethal weapons.
The Federal Bureau of Investigation warned in 2002 that al-Qaida might be planning to attack trains in the United States, possibly causing derailments or blowing up tank cars laden with hazardous materials. And after bombings on commuter trains killed 191 people in Spain last March, domestic U.S. security officials secretly persuaded one railroad to reroute toxic shipments that had routinely passed within four blocks of the Capitol in Washington, government officials said.
Federal authorities have been working with railroads and the chemical industry to improve security for trains. But there is still much to be done, particularly given the structural weaknesses of many tank cars, current and former federal officials say.
George Gavalla, a former associate administrator for safety at the Federal Railroad Administration, said railroads had promised to beef up security when there was a credible terrorist threat.
So when such a threat arose a year ago in Las Vegas, Gavalla said, he sent an inspector there on New Year's Eve to assess the security measures in place. Those measures, he said, were virtually nonexistent.
When the inspector visited a rail yard 13 miles from the airport, he found no one watching over six tank cars with markings indicating that they might contain chlorine gas, according to a memorandum that he wrote about his visit. Two hours later, he visited another rail yard with four tank cars possibly carrying poisonous gas and they, too, were unguarded, the memorandum stated.
Finally, Gavalla said, the inspector visited a rail yard near several hotels. "None of the train crew members challenged me or even talked to me," the inspector wrote. A spokesman for the railroad administration declined to comment on the report.
Railroad officials have said that they have taken many steps to improve security. Nancy L. Wilson, a senior vice president of the Association of American Railroads, said in a statement about the same time as the inspection that the railroads had "tightened security and intensified inspections across their systems."
Police forces employed by the major railroads, Wilson said, had "put into place more than 50 countermeasures to ensure the security of the industry."
Just how ruptured tank cars can endanger a community was underscored three years ago when a Canadian Pacific Railway freight train derailed just outside Minot, N.D. Five tank cars carrying a liquefied type of ammonia gas broke open, releasing toxic fumes that killed one resident and injured more than 300.
The National Transportation Safety Board, in a report on the accident released last year, said that the steel shells on the five ruptured tank cars had become brittle, causing a "catastrophic fracture" that released clouds of toxic vapors. Those cars, the safety board found, were built before 1989 using steel that did not _ as it does now _ undergo a special heat treatment to make it stronger and less brittle. Tank cars built after 1989 use this steel.
The safety board warned that of the 60,000 pressurized tank cars in operation, more than half were older cars that were not built according to current industry standards, leaving them susceptible to rupture. And because these cars may remain in service for up to 50 years, some older ones could still be hauling hazardous materials until 2039.
Among the hazardous materials carried by the tank cars are liquefied ammonia, chlorine, propane and vinyl chloride. In most cases, chemical or leasing companies own the cars, not the railroads.
Although the rail industry now requires that tank shells be made with the special, heat-treated steel, the safety board said that treatment alone "does not guarantee" enough protection against impact. Other techniques also should be explored, the board said, but it cautioned that the industry and the railroad administration "have not established adequate testing standards to measure the impact resistance for steels and other materials used in the construction of pressure tank cars."
Steven W. Kulm, a spokesman for the railroad administration, said, "We have a long history of activities and actions that have improved the integrity of tank car construction." Kulm said that since 1994, accidents "have been few in number," though even one death, he added, was too many. "Tank cars are more crashworthy and puncture resistant in train derailments today than ever before."
In the Texas crash last summer, the tank car that ruptured and released poisonous gas was made before 1989, though federal investigators have not yet concluded whether brittle steel played a role in that accident.
The South Carolina crash involved the rupture of a newer tank car manufactured in 1993, said Richard Koch, vice president for public affairs at the Olin Corp., a diversified manufacturing company that owned the car.
Koch said that tanker had been recertified to carry hazardous materials last June.
Railroad and chemical executives formed a task force to study the safety board recommendations, and it has been conducting crash tests on tank cars.
Michael E. Lyden, the vice president for storage and transport at the Chlorine Institute, a trade group in Arlington, Va., said the leading companies were "working in a cooperative manner to improve the pressure vessels."
Industry officials said the group could recommend the retirement of cars made by certain manufacturers or suggest that some types of cars carry less hazardous materials.
Security experts said the recent accidents also illustrated the harm that terrorists could cause if they attacked trains carrying highly toxic substances. Some cars are also used to store chemicals at water-treatment, sewage and industrial plants.
"Whether it's an accident or al-Qaida, these hazardous materials are very vulnerable and pose a great risk to densely populated areas," said Rep. Edward J. Markey, D-Mass., who has pushed for greater rail security.
The danger of such an attack has been a major concern since the Sept. 11 strikes. When the United States invaded Afghanistan in October 2001, freight railroads placed a 72-hour moratorium on carrying some hazardous chemicals as a precaution against retaliatory strikes.
The fears have been most evident among officials in Washington, some of whom have pushed for a year to ban toxic rail shipments through the capital. An expert from the Naval Research Laboratory testified last January that more than 100,000 people could be at risk of death or injury if one of the tank cars exploded there.
Federal and railroad officials have opposed a ban, saying that rerouting the shipments could lengthen transits and upset other communities.
But late last year, officials from the Department of Homeland Security told congressmen that after the Madrid bombings they had quietly asked the CSX Corp., a leading railroad, to shift some of the shipments away from Washington, Markey said.
The officials also said they were working on a $6-million security plan that would increase surveillance of 42 miles of railroad track in the Washington area.
Since last August, the Department of Homeland Security and the Department of Transportation have been looking at whether to require greater security for toxic rail shipments nationwide. The agencies have said they are considering several possible measures, including better identification and tracking of the most toxic substances and "strengthened tank car integrity."