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Harvard University poisoning: What is sodium azide, anyway?

October 26, 2009 |  6:15 pm

In August, six Harvard Medical School scientists were sickened after drinking coffee from a communal coffee machine: Turns out it was laced with a chemical called sodium azide. The poisoning was revealed last week in an internal memo to faculty at Harvard.

In this ABC News story, one of the sickened scientists, Matteo Iannacone, talked to the press about the experience. Iannacone said he didn't see how the poisoning -- which is being investigated by police -- could have been unintentional. Upon drinking the coffee, he felt dizzy and his heart started beating rapidly. Some scientists fainted.

If you're curious about what sodium azide is, here are a few facts and links.

From safety guidelines at Northeastern University: "a colorless, odorless, crystalline solid (salt-like) or solution. It is soluble in water or liquid ammonia, slightly soluble in alcohols, and insoluble in ether. It is highly toxic and presents a severe explosion risk when shocked or heated." It shouldn't be poured down drains because it will react with heavy metals to form lead azide and copper azide, which are highly explosive.

And from a material safety data sheet from the chemical company Mallinckrodt Baker, on the dangers of ingestion: "Highly Toxic! May cause breathlessness, pulmonary edema and rapid heart beat within 5 minutes. Nausea, vomiting, headache, restlessness, and diarrhea may occur within 15 minutes. Other symptoms may include low blood pressure, abnormal breathing, reduced body temperature, reduced body pH, convulsions, collapse and death."

Sodium azide inhibits the respiratory enzyme cytochrome oxidase, as does carbon monoxide, and as a consequence cells are asphyxiated.

And it is a potent vasodilator -- meaning that it relaxes blood vessels -- hence the dangerous and potentially fatal drop in blood pressure that people experience upon exposure. According to a review in the International Journal of Toxicology (and other sources), this is the most common effect regardless of whether the chemical was inhaled or ingested. Because of this vessel-relaxing property, in the past, sodium azide has been reviewed as a potential antihypertensive drug.

Sodium azide is also used in airbags and airplane escape chutes as a generator of nitrogen gas that fills the bags/chutes: No toxicity has been reported from spent airbags, according to a review on the chemical in a book "Poisoning and Drug Overdose." The review also notes that healthcare workers need to be very careful when dealing with patients who have suffered severe sodium azide poisoning from ingestion because the chemical will react with stomach acids and produce a chemical called hydrazoic acid, which is toxic and explosive.

More information is at the website for the Centers for Disease Control and Prevention.

Sodium azide is used commonly as a preservative so that bacteria don't grow in chemical reagents that are going to be used in experiments. So research labs that do biochemical experiments of some kind are likely to have some around.

--Rosie Mestel

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