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Re: [TCML] DC Coil progress.



On 11/22/13 5:32 AM, Futuret wrote:
> I've heard that vaporized zinc (from the galvanizing) is
> extremely toxic.  Whenever I've tried using brass
> electrodes they eroded away very quickly.  I've had
> much better results with copper electrodes.  Others
> may have had different results, but I thought I'd
> mention it.
>

I don't know about "extremely".  It's zinc oxide, which is non-toxic, 
but it does cause "tinner's tummy" or "zinc fume fever" and welders who 
have to work with galvanized iron often call in sick the next day, 
although the mechanism is unclear.  There are some theories that there 
is zinc chloride involved, or that it is a general reaction to a foreign 
material/heavy metal.

It's not in the Hydrogen Cyanide, Hydrogen Sulfide sort of class. The 
IDLH (Immediately dangerous to life and health) for H2S is 100 ppm (150 
mg/m3).  The ACGIH recommendation for H2S is 1 ppm (1.4 mg/m3) TWA.  HCN 
is similar (IDLH of 50ppm, typically tolerated by humans for 30min, 
100-130 ppm is fatal after 0.5-1 hr)

As it happens, the OSHA Permissible Exposure limit for Zinc Oxide Fumes 
is quite low: 5mg/m3 total weighted average (TWA) over 8 hour day. but 
there's no IDLH level, and it's not clear that you can die (immediately) 
from it.  CDC says:"Studies in the workplace have shown that welders 
exposed to zinc oxide fume at concentrations of 320 to 580 mg/m3 
reported nausea, with the development of chills, shortness of breath, 
and severe chest pains 2 to 12 hours later."  And some guinea pigs gave 
up the ghost: "The animals in the high-exposure group (2500 mg/m3 for 
three to four hours) died after exposure."

But the 2.5 GRAMS/cubic meter that caused the rodent demise is a LOT of 
fumes.  It would be an exceedingly dense cloud at that level.  You could 
probably see the particulate fumes at 10mg/m3.



pubmed has
http://www.ncbi.nlm.nih.gov/pubmed/11094787

The OSHA(etc) limit is 5mg/m3 total weighted average (TWA) over 8 hour day.

Zinc oxide fume is a respiratory irritant that causes metal fume fever 
and can temporarily decrease lung function for up to 48 hours after 
exposure (ACGIH 2003).

The effects of metal fume fever may be delayed a few hours after initial 
exposure (NIOSH/IPCS 2004).

The inhalation of zinc oxide at the PEL concentration for two hours by 
naïve subjects was reported to trigger an inflammatory response 
involving the release of cytokines, thought to mediate the symptoms of 
metal fume fever (chills, elevated body temperature, myalgia, cough, 
fatigue, chest pain, nausea, and vomiting) that peaked about nine hours 
after exposure. Prior zinc oxide exposure resulted in the development of 
some tolerance (desensitization) to these inflammatory effects (Fine et 
al. 2000; Kuschner et al. 1997).


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