Date: Tue, 11 May 2010 09:29:52 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
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From: ILPI <info**At_Symbol_Here**ILPI.COM>
Subject: Re: 3 re: Hg response
In-Reply-To: <053E9EF31C54468AB37AE2E986364CFC**At_Symbol_Here**bruekbergterm1>

It's clear from the discussion here that many just don't appreciate the nature of mercury, and that many of those commenting have never actually handled the material.

Permit me to address a few points:

1. Taking students to the hospital for "decontamination" was over-reaction, absolutely yes.  It was also the worst thing that could have been done if there was serious contamination.  That would have spread the mess to the transport vehicles, the hospital, etc. etc. etc..

2. The ability of mercury to "shatter" into tiny, tiny droplets literally increases its surface area by a factor of **one million** compared to a single small pool.   This not only makes cleanup very difficult, it makes the evaporation rate increase by orders of magnitude.  As one doesn't know the size and physical distribution of the droplets, any calculations about how long it would take to all evaporate is nothing more than complete conjecture, whether we're guessing at how long it would take all the mercury to "go away" or whether the concentrations would become dangerous.

3. Thus, discussion of whether mercury vapor would saturate in a room is a pointless paper exercise given the number of variables.   It is a question whether the vapor concentration will begin to approach a dangerous level, a level which is well below saturation.  The only way to do that is to measure the levels.  And a measurement taken at the peak of the workday with high turnover will almost certainly differ from one taken in the morning after a night of low air turnover.

4. The (always reliable; roll eyes) media report that there were 3 contamination sites within the school, and it's obvious that one can't simply assume that those were the only ones, 0105110317  In any high-traffic area, the mercury will be spread far and wide.  So if kids played with it in a cafeteria, then it was no doubt tracked throughout the school, although in a decreasing amount with respect to distance from the original spill area.  The article I just referenced mentions that the building went into lockdown, which is surprisingly smart with respect to determining which areas were contaminated and keeping the spilled material from being spread further.

5. Most attempts to sweep up mercury simply break it up into smaller bits and spread it around.  And vacuuming is obviously out.  We'd expect that the untrained personnel who first noticed the situation would have tried one of those two methods before HazMat was ever called .   BTW, sprinkling sulfur on spills is basically useless as the rate of reaction of solid sulfur with mercury is exceedingly slow.  I have always preferred zinc powder, which amalgamates mercury quite well.

6.  As mercury amalgamates with common metals with the exception of iron/steel, it can evaporate into the room, react with a desk, lighting fixture, soda machine, whatever, and then continue to pose a long-term health hazard.  Again, air monitoring is the only way to determine if the risk is real.

In short, closing the school in order to a) ensure that the extent and amount of the spill was accurate determined, b)  prevent further distribution/spread of the mercury, and c) ensure that monitoring results were negative was a prudent precaution when dealing with an unknown level of hazard.  Better to close it and find out afterward that the risk was minimal than to later find that the risk was real and underestimated.

I have collected some mercury thoughts, tips, and precautions here: y/mercury.html

Rob Toreki

On May 11, 2010, at 7:43 AM, Ben Ruekberg wrote:

Not wishing to be disputatious concerning the hazards of mercury, nonetheless, I think before worrying about the saturation vapor pressure of mercury, I suspect that one should also consider the rate of evaporation of mercury as well.  I don=92t know what it is, but were it all that significant people would probably have to have been refilling McLoed gauges with some frequency.  In fact, I don=92t recall that ever being necessary, nor do I recall finding significant amounts of mercury in the Nitrogen traps of vacuum systems under normal circumstances.  Given that most rooms have reasonable air exchange, I suspect that rooms seldom reach saturation.
To refer to the example of 5 mg of mercury reaching the saturation concentration of 15 mg m^-3, one would be dealing with a room with a volume of 1/3 m^3, an unusually small room.  A 20=92 X 20=92 X 10=92 room would hold (at saturation, with no air exchange) ~ 1.6 g of mercury, a mere drop, but if a drop of mercury evaporated at a significant rate an amount that might be noticeable.
What I am suggesting is that the rate of evaporation might be more important than the saturation vapor pressure and may reduce the hazard (at least for the short term) and that one might not need to be overly alarmed.
Thank you,

From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**LIST.UVM.EDU] On Behalf Of List Moderator
Sent: Tuesday, May 11, 2010 7:16 AM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: Re: [DCHAS-L] 3 re: Hg response
From: "Allan Astrup Jensen" <aaj**At_Symbol_Here**>
Date: May 11, 2010 5:26:29 AM EDT
Subject: RE: [DCHAS-L] 3 re: Hg response
Please, don=92t underestimate the danger of mercury vapour!
Mercury vapour is dangerous, and it is difficult to clean up indoor spills completely. Even the 5 mg Hg from a crushed light bulb indoors can create dangerous air concentrations, as many publications have shown. The saturated air concentration at room temperature is about 15 mg Hg/m3. That concentration is 500 times higher than the TLV, and such exposures have resulted in serious intoxications.
Yours truly,
Allan Astrup Jensen 
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Secretariat for Metrology, Chemical analysis and Management Systems 
FORCE Technology, Br=F8ndby 
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