ROBERT SIEGEL, HOST:
What caused Wednesday night's massive explosions in Tianjin, China, explosions that killed more than 50 people and injured hundreds more? What's known is that the explosions originated from a warehouse owned by a Chinese company that stored and handled dangerous chemicals. Chinese authorities have not given a detailed list of what those chemicals were, though. David Leggett is a consultant on hazardous chemical risk assessments, and he joins us now to talk about the chemicals that have been confirmed and chemicals that might have been at the site. Welcome to the program.
DAVID LEGGETT: Thank you.
SIEGEL: From what the company's website has acknowledged and what has been reported elsewhere, can you imagine what chemicals might've been at this warehouse that might've combined in such a way to produce such a massive explosion?
LEGGETT: As far as we can see right now, there are three chemicals that are confirmed - calcium carbide, potassium nitrate and sodium nitrate. And those three together, if left alone and not in the presence of fire, are relatively stable. However, in the presence of a fire - a very big fire, as we believe there was - the first thing that probably happens is that the containers of the calcium carbide start to fail. At the same time, one can expect to see that the water supplies in the warehouse may be beginning to fail. And if we get calcium carbide, especially if it's hot, mixed with water, we form a very, very flammable and highly explosive gas called acetylene.
SIEGEL: This is a transit warehouse, I gather, which means that at any given time, there could be different chemicals present in it depending on what the company is transporting where. Does that mean that local firefighters should be informed daily what's inside the warehouse, or is that practical?
LEGGETT: Yes and no. Let's take the example of America. America, where you have these sorts of transit warehouses, material safety data sheets accompany chemicals, and a good, well-run company will have a list of these material data safety sheets for every single chemical that will be in the facility, even if it's only there for 12 hours, with the result that when the firefighters have to show up to do a firefighting activity, they will have the ability to refer to the material safety data sheets which can help them understand the best way to fight a fire. Translate that into China, and the piece, I think, is missing is, what is the level of documentation that would go with the chemicals that are passing through this transit facility?
SIEGEL: You would question whether the documentation is thorough and accurate.
LEGGETT: Frankly, without knowing, and seeing the past history of China and their chemical explosions, yes, I would question that.
SIEGEL: A local safety administration official in Tianjin said that the chemical sodium cyanide was detected in the sewer system near the warehouse. If that's present, does that say anything to you about what might've caused or exacerbated the explosion?
LEGGETT: In an explosion, there is always the result of lots of debris being thrown around all over place. So finding it in the sewer, in my mind, is not a surprise.
SIEGEL: I mean, China is - has been noted for some terrible industrial accidents. When Americans see these pictures of a massive explosion at a port warehouse facility, should we be seriously concerned that this could happen at our local port and we could witness such a thing, or do we have a significantly better system than they do?
LEGGETT: I really believe we have a significantly better system, which does not mean that it can't happen. Handled properly and handled appropriately, it's a very safe system. If you don't get the handling right, then you are asking for trouble.
SIEGEL: Given the possibilities of what was in the warehouse - what chemicals were in the warehouse - would you assume that there are dangers going forward for the local air and water as a result of this?
LEGGETT: Depending upon the amount of sodium cyanide that is there, I would be concerned about the residues of sodium cyanide that may have been distributed across the area and how that cleanup will be managed. The other chemicals - calcium carbide is probably going to have been consumed either by the fire or by firefighting activities.
SIEGEL: Dr. Leggett, thank you very much for talking with us.
LEGGETT: You're very welcome. Thank you.
SIEGEL: David Leggett is as a consultant on hazardous chemical risk assessments, and he spoke to us from NPR West.
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