I've received several helpful answers to my question so far (see below). To clarify, I should point out that I'm interested in proper storage practices of millimolar solutions rather than disposal of these solutions or precaution associated with the solid. The question is whether the solutions need to be labelled with hazard warnings or have secondary containment because of their toxicity. Based on the DeLaHunt calculation below, I believe not... I would note that the ingestion fatality referred to below (I believe) came up in a google search on "sodium azide death" and involved a solution of 1 gram/liter. - Ralph Subject: RE: Sodium azide solutions Date: Fri, 5 Sep 2003 09:03:32 -0600 From: "John DeLaHunt"
Ralph Stuart asks: > Has anyone tried to define the line between a "non-hazardous" > and "hazardous" solution of sodium azide? The Laboratory > Chemical Safety Summary in Prudent Practices seems to address > only the solid form. EPA has. Sole active ingredient blah blah blah. We all agree how effective EPA regulation is at protecting public health and environment in labs. > We have many people using it at millimolar levels to control > biological activity in nutrient solutions. I don't believe that > this use presents a toxicity hazard for chemical hygiene plan > purposes. However, the natural question is "Is it only the solid > form of sodium azide that is potentially toxic, either acutely > or chronically?" "At what concentration would the toxicity concern > become neglible?" We use colorimetric tests (from Armour, Browne & Weir) to test for presence of azide. That's a pretty dern sensitive test (about 1 ppm). If it doesn't hit for azide using that test, we call it non-azide containing and drain it. Esp on the used solutions which don't have the acute haz waste monkey business. Sigma/Aldrich says the LD50 is 27 mg/kg. A 1:111 solution in water (it says here) has an LD50 of 3000 mg/kg, which is about the LD50 of table salt. > Thanks for any insight on this. Hope it helps. John John DeLaHunt Environmental Health & Safety Manager The Colorado College 1125 Glen Avenue Colorado Springs, CO 80905 (719)389-6678 (vox) (719)389-6981 (fax) jdelahunt**At_Symbol_Here**ColoradoCollege.edu www.ColoradoCollege.edu ===== From: "Greene, Ben" To: "'Ralph Stuart, University of Vermont'" Subject: RE: Sodium azide solutions Date: Fri, 5 Sep 2003 09:03:46 -0600 Status: Hi Ralph - I suppose you could do a volume/concentration calculation to back out the mass of sodium azide in the dilute solutions. You could relate that mass to LD50 values. However, with some of the azide work I was involved with, I was also concerned with handling, storage, and disposal of the dilute solutions, as mixing or contact with heavy metals can form substances which can be explosive if dried (such as might occur in between a cap and a bottle or a glass stopper and a volumetric flask, and mixing with acid can evolve hydroazoic acid that is highly toxic. Ben ===== Date: Fri, 05 Sep 2003 08:14:50 -0700 Subject: Re: [DCHAS-L] Sodium azide solutions From: "Teresa Robertson" Hi Ralph, There was a post a year or two ago on one of the listservs about a college student who died. The student drank a saline solution for a lab. The tech who prepared the solution was not told the solution was for consumption and added sodium azide as a preservative. I do not recall who posted or which school, but maybe that will give you a lead.... :) Teresa Teresa R. Robertson, B.S., NRCC-CHO Certified Chemical Hygiene Officer Instructional Support, Chemistry Department Natural Sciences and Mathematics California State University 9001 Stockdale Highway, Bakersfield, CA 93311-1099 Member of: The Laboratory Safety Institute (LSI), The American Chemical Society (ACS), The National Registry of Certified Chemists (NRCC), The National Association of Chemical Hygiene Officers (NACHO) The National Association of Scientific Materials Managers (NAOSMM) ==== From: "Rau, Edward (NIH/OD/ORS)" Subject: RE: [DCHAS-L] Sodium azide solutions Date: Fri, 5 Sep 2003 11:39:10 -0400 Ralph, Sodium azide is quite stable in water and the minimal dose that can cause hypotension in humans lies between 0.2 and 0.4 ug/kg, so your "negligible" aqueous concentration for acute exposures would be below that number. Accidental lab ingestions in the tens of milligrams range have produced serious acute effects. Animal studies (dogs) indicate adverse effects from chronic oral exposures - doses in the range of 1 to 10 mg/kg/day. It is also mutagenic in several assays. At the NIH we manage all solutions containing sodium azide as hazardous waste, regardless of concentration. While these spent, dilute solutions are not federally regulated as hazardous waste, this approach assures that the material is collected and disposed of off-site, rather than being discharged down the drain where it has the potential to form reactive compounds on metal plumbing components. Another thought - while it is difficult to define what concentration is toxic for chemical hygiene plan purposes, the level of concern in waste water discharges may be even lower because of potential adverse impacts on biological wastewater treatment systems at very low levels. Of course the best approach is source reduction - use of alternative preservatives whenever feasible. --Ed Edward H. Rau, R.S., M.S. Captain, U.S. Public Health Service Environmental Health Officer Environmental Protection Division, ORF DHHS-National Institutes of Health 13 South Drive, Room 2W64 Bethesda, MD 20892-5746 (301) 496-7775 (301) 480-8056 (Fax) raue**At_Symbol_Here**mail.nih.gov -----O ==== Date: Fri, 05 Sep 2003 10:45:08 -0500 From: wayne wolsey Subject: Re: [DCHAS-L] Sodium azide solutions Unfortunately I am packing to leave for the ACS meeting in New York and don't have time to check reference works on this, but about 38 years ago while still in industry I worked on a project involving the synthesis of sodium azide. An unspected hazard involving aqueous alkali metal azides is that if acidified, the aqueous solution at high concentration of hydrazoic acid can explode. My recollection is that this occurs at about 37% HN3. Also, HN3 vapor can be emitted by acidified azide solutions at any concentration. Workers should also consult the MSDS info on HN3 as well as NaN3. Another latent azide hazard is disposal of aqueous solutions down the drains. Over a period of time, azide solutions will form a coating of metal azide on the inside of the drain pipes. There were some infamous accidents some years ago involving azide solutins coming out of a Coulter Counter (used to measure blood cell levels) going down a drain. When a plumber took apart the drain pipe (or perhaps cut it with a hacksaw), an explosion occurred. Covalent, heavy metal azides, such as copper and lead are shock sensitive--and are even used as igniters for military explosives. Sorry that I can't provide citations at this time--but your researchers should proceed with caution. Wayne Wolsey Professor of Chemistry Macalester College St. Paul, MN ===== Date: Fri, 05 Sep 2003 11:52:09 -0400 From: Ben Ruekberg Organization: University of Rhode Island Subject: Sodium Azide It is my understanding that dilution does not influence hazardous/non-hazardous until you get into really, really small amounts. So I would not try to reclassify azides even at millimolar levels, but that is my opinion. Anecdote has it that azide was used to preserve blood samples and these samples were discarded in the sink, where the azide reacted with the metal in the plumbing. When someone tried to repair a leak in the drainpipe the metal azide exploded. ======= Subject: Re: [DCHAS-L] Sodium azide solutions From: Jay Rappaport Thimersol is a mercury containing preservative used in multidose vaccines as a preservative. It has been suggested that it is responsible for cases of autism in children. Sodium azide is a mitochondrial toxin, decoupling oxidative phosphorylation from the electron transport chain. What this means is the generation of heat instead of the capture of energy as ATP. I do know of one case of death resulting from ingestion of sodium azide solution by a laboratory worker. Jay Rappaport, Ph.D. Chair, IBC Professor, Temple University Center for NeuroVirology and Cancer Biology 1900 N. 12th Street, Biology/Life Sciences Bld. Rm 224B-N Philadelphia, PA 19122 Tel 215-204-0605 Fax 215-204-0639 ===== From: "Joanne Myers" Subject: Re: [DCHAS-L] Sodium azide solutions Date: Fri, 5 Sep 2003 08:57:59 -0700 Sodium Azide is explosive in solid form. It has been used in airbags for vehicles to create the sudden expansion of gas. But the solution form is toxic, as it must be to control microbial growth. And if released into the sewer system or waterways it would also have the effect of controlling microbial growth, so there is a hazard to microbial sewage treatment systems. As to toxicity in the lab, to lab personnel, normal prudent lab practices would apply. Many clinical laboratory uses involve a pre-mixed solution in a disposable plastic dispenser, which fits directly into automated machinery. But you may be mixing your own solution from dry powder. As any dry powder could be dispersed, and subsequently inhaled or contact mucous membranes of the eye or mouth, such mixing operations should be done with appropriate local ventilation controls. You might even be able to obtain the material in pre-weighed pillow packs which can be dissolved in the solution you wish to preserve. -- Ralph Stuart, CIH Environmental Safety Manager University of Vermont Environmental Safety Facility 667 Spear St. Burlington, VT 05405 rstuart**At_Symbol_Here**uvm.edu fax: (802)656-5407 Owner: SAFETY list (general discussion of environmental health and safety) LAB-XL list (performance oriented environmental regulation of laboratories)
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