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Methanol and Blindness
Name: Roxanna
Status: student
Grade: 9-12
Location:CA
Country: N/A
Date: 5/9/2005
Question:
I am a chemistry student and we are learning of all the
different types of alcohols. I was wondering what is in methanol that
makes people go blind?
Replies:
Roxanna,
A biochemist will probably do a better job at answering your question, but
I'll give it a shot. When methanol (CH3OH) is ingested, it is acted upon
by an enzyme called alcohol dehydrogenase and the result is the production
of formaldehyde (CH2O). [You will note that the net effect is the removal
of two hydrogens and the formation of a double-bond between the carbon and
oxygen.] Formaldehyde can migrate to the brain where it can damage the
optic nerves (I am not sure if it is clearly known how this happens).
Greg (Roberto Gregorious)
Hi Roxanna
If ingested, methanol undergoes dehydrogenation in the
liver by the way of a local enzyme and formaldehyde
is produced as a result. Formaldehyde and related
compounds such as formic acid have a huge ocular
toxicity, the vision becomes blurred, it happens a
central scotoma (central vision is lost) and
eventually blindness happens.
Methanol toxicity in humans (also in monkeys) is
characterized by a latent period of many hours
followed by a metabolic acidosis and ocular toxicity.
The metabolic acidosis and blindness is apparently due
to formic acid accumulation in humans and monkeys.
The accumulation of formate is due to a deficiency in
formate metabolism which is, in turn, related, in
part, to low hepatic tetrahydrofolate (H4 folate).
Thanks for asking NEWTON!
Mabel
(Dr. Mabel M. Rodrigues)
Roxanna,
Methyl alcohol possesses distinct narcotic properties. Its main toxic
effect is exerted upon the nervous system, particularly the optic nerves
and possibly the retinae. The effect upon the eyes has been attributed to
optic neuritis, which subsides but is followed by atrophy of the optic
nerve. Once absorbed into the body, methanol is only very slowly
eliminated. Coma resulting from massive exposures may last up to 2-4
days. In the body, the products formed by methanol oxidation are
formaldehyde and formic acid, both of which are toxic. I trust that this
helps.
Sincerely,
Bob Trach
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Update: June 2012
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