Wednesday, May 29, 2013

Derailed Train Explodes in Baltimore Carrying Toxics

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.
But mostly, it's just a very potent oxidizer, which if in contact with some organic materials or some acids if heated.  This is probably what caused the explosion seen and heard on the video linked below
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.
So there's your organic acid, waiting to be mixed with the sodium chlorate and heated...
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.
Hexafluorosilicic acid releases hydrogen fluoride when evaporated, so it has similar risks. It is corrosive and may cause fluoride poisoning; inhalation of the vapors may cause lung edema. Like hydrogen fluoride, it attacks glass and stoneware. LD50 value of hexafluorosilicic acid is 70 mg/kg.
Hydrogen fluoride (HF) is a deadly toxin.  And so there were had the fire to make the HF.  Nice mixture; it's kind of a miracle, and a testament to the care of the first responders, that no one was hurt of killed.

A pretty amusing video of taken by passersby of the the explosion.  The commentary is PG (at best)... 

No comments:

Post a Comment