The freight train that derailed Tuesday in Rosedale carried one chemical classified as hazardous by the U.S. Department of Transportation and another that also posed risks for firefighters and others at the scene even though not similarly classified.
There might have been residues aboard of a third chemical that also is highly corrosive and hazardous. State health officials, however, said the incident represented only a low risk to the public.
CSX spokesman Gary Sease said at least one of the dozen rail cars that appeared to be involved in the derailment contained sodium chlorate. The chemical is used in making a variety of products, including herbicides, explosives, dyes, cosmetics, pharmaceuticals and papers, according to a Material Safety Data Sheet prepared by the New Jersey Department of Health and Senior Services.
Sodium chlorate does not burn, but poisonous gases can be produced in a fire, the data sheet says. It is also considered a "strong oxidizer," which could enhance combustion of other materials. Contact can irritate eyes and skin, and it can cause headaches, fatigue, dizziness and death at very high concentrations if inhaled. Ingesting the chemical can damage the liver and kidneys.
Four of the train's cars held terephthalic acid, the CSX spokesman said, and one of them caught fire, according to Baltimore County officials.
Terephthalic acid is used in making plastics and other products. The Department of Transportation does not list it as a hazardous material, Sease said. But it can irritate skin, eyes, nose, throat and lungs and cause coughing, wheezing and shortness of breath if inhaled, according to the data sheet. Though it does not readily ignite, terephthalic acid can burn, producing harmful gas.
A fact sheet prepared by the U.S. Occupational Safety and Health Administration advises emergency responders dealing with spills to isolate them and protect people downwind from potential exposure.
County officials said the second of the two cars that caught fire contained fluorosilicic acid. Sease, the CSX spokesman, said the train included a "residue car" that might have included traces of the chemical.
Though it does not burn, fluorosilicic acid is highly corrosive and contact with it in liquid or vapor form can cause severe irritation and chemical burns of the eyes, skin, mucous membranes and respiratory tract, according to a safety sheet by KC Industries, a Florida-based chemical manufacturer.
Two other cars that derailed were carrying different chemicals, county officials said, but those cars are intact and were not considered a threat.
After consulting with Baltimore County emergency officials and CSX, the Maryland Department of Health and Mental Hygiene said in a statement that the situation posed little threat to people nearby. Neither of the main chemicals involved should produce an "imminent hazard" to the general public, the department said, and preliminary monitoring did not indicate the presence of any highly toxic chemicals.
A spokesman for the Maryland Department of the Environment, which had personnel at the scene, directed questions to the county.