[Jewelry making - Article 00705] - Re: [Orchid] Methanol & Toxicity

[FrodoGem]

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>     How much methanol would it take to blind a person? 

    Information I found on the internet (take it for what it's worth) is
    that cases of blindness have occurred with ingestion of as little as
    15 mg.  Remember that there is a difference in effects between
    different routes of exposure...ingestion, inhalation, skin
    absorbtion... 

    Blindness is an acute effect that occurs when the levels in the 
    blood reach a certain level.  In a shop exposure, that can happen
    over a period of time when the intake rate from exposure exceeds the
    normal elimination rate of the body. 

    I found no information comparing toxicity from different routes of
    exposure but the toxicity of some contaminants can vary considerably
    with different routes of exposure.  As far as acute effects go, I do
    not believe there is much danger with the type of exposure we would
    encounter at a jeweler's bench unless there were a spill.  Spills,
    of course carry a great fire danger also.  The large surface area of
    a spill can greatly increase skin absorption or evaporation into the
    air leading to inhalation exposure.  One square foot of skin
    exposure will absorb almost 1000 times as much per minute as one
    square centimeter.  The skin in the lap area (male) can absorb as
    much as 50 times as fast as the soles of the feet. 

    You may want to follow this thread (still a relatively small thread)
    back to last weekend where I discussed chronic health effects
    briefly.  

    I want to add one thing here...chronic effects may or may not have a
    threshold exposure level of advere effects.  That is, you may be
    exposed to some things over time and never have any chances of long
    term ill effects so long as you hold your exposure below a certain
    level.  With other contaminants very small damage with each exposure
    accumulates into long term adverse effects.  Methanol may be one of
    the latter. 

    In researching this further on the internet, I found considerable
    controversy regarding methanol metabolites from a popular artificial
    sweetener.  I also found that there is not much research about the
    chronic effects of methanol.  here is a link to one articl I found
    using google terms "Chronic Methanol:" 

    http://tinyurl.com/66suw 

    Note that the "chronic" levels administered were probably nearly
    high enough to cause acute blindness (I didn't research those levels
    in rats and have no idea what the rat's elimination rate was.  The
    levels used in the study are certainly high enough to produce a risk
    of acute blindness in humans) 

    I haven't been too excited about long term effects because I keep
    thinking if they existed and were serious, I would have heard about
    them by now.  (I thought the same thing as I was reading the first
    news articles about asbestos back in the 1960's) 

    I use methanol in my water torch and plan to contiune doing so; it
    is mostly consumed by the flame.  As I research this further, I am
    becoming more convinced that if it is used for a boric acid dip,
    proper ventilation is critical just as it makes good sense for
    everything else we get exposed to around the studio.  It is common
    sense to always limit exposure to all contaminants. 

Howard Woods
Eagle Idaho

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