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Subject: Re: 3 re: Hg response
Date: Tue, 11 May 2010 14:23:53 +0200
Author: Allan Astrup Jensen
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Subject: Re: 3 re: Hg response
Date: Tue, 11 May 2010 10:01:45 -0400
Author: Ben Ruekberg
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Date: Tue, 11 May 2010 09:29:52 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
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,
http://www.poughkeepsiejournal.com/apps/pbcs.dll/article?AID=2
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.
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,
Ben
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.
Allan Astrup Jensen
Technical Vice President
Secretariat for
Metrology, Chemical analysis and Management Systems
FORCE Technology, Br=F8ndby
Park All=E9 345
2605 Br=F8ndby
Phone: +45 43 26 70 00
Direct: +45 43 26 70
81
Mobile: +45 40 94 10 22
Fax: +45 43 26 70
11
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