Date: Fri, 5 Sep 2003 12:31:39 -0400
Reply-To: "Ralph Stuart, University of Vermont" <rstuart**At_Symbol_Here**>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Ralph Stuart, University of Vermont" <rstuart**At_Symbol_Here**>
Subject: Sodium azide solutions, part 2
Comments: To: SAFETY**At_Symbol_Here**LIST.UVM.EDU

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

>  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

>  Thanks for any insight on this.

Hope it helps.


John DeLaHunt
Environmental Health & Safety Manager
The Colorado College
1125 Glen Avenue
Colorado Springs, CO  80905
(719)389-6678 (vox)
(719)389-6981 (fax)


From: "Greene, Ben" 
To: "'Ralph Stuart, University of Vermont'" 
Subject: RE: Sodium azide solutions
Date: Fri, 5 Sep 2003 09:03:46 -0600

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


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


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

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.


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)


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

Temple University
Center for NeuroVirology and Cancer Biology
1900 N. 12th  Street, Biology/Life Sciences Bld. Rm 224B-N
Philadelphia, PA

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

fax: (802)656-5407

SAFETY list (general discussion of environmental health and safety)
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