why is the ingestion of methanol more fatal than ethanol?

Answer 1

It's chemistry, sort of. Another question is why is sodium so ready to burn and chlorine so poisonous to breath, but when they get together they form salt which helps preserve life? Maybe a chemist can give a better answer, but it has to do with the way they chemically interact with our bodies, well not mine anyway.

Answer 2

Methanol is intoxicating but not directly poisonous. It is toxic by its breakdown (toxication) by the enzyme alcohol dehydrogenase in the liver by forming formic acid and formaldehyde which cause blindness by destruction of the optic nerve. [2] Methanol ingestion can also be fatal due to its CNS depressant properties in the same manner as ethanol poisoning. It enters the body by ingestion, inhalation, or absorption through the skin. Fetal tissue will not tolerate methanol. Dangerous doses will build up if a person is regularly exposed to vapors or handles liquid without skin protection. If methanol has been ingested, a doctor should be contacted immediately. The usual fatal dose: 100–125 mL (4 fl oz). Toxic effects take hours to start, and effective antidotes can often prevent permanent damage. This is treated using ethanol or fomepizole[3]. Either of these drugs acts to slow down the action of alcohol dehydrogenase on methanol by means of competitive inhibition, so that it is excreted by the kidneys rather than being transformed into toxic metabolites. Though it is miscible with water, methanol is very hard to wash off the skin; it is best to treat methanol like gasoline.

The initial symptoms of methanol intoxication are those of central nervous system depression: headache, dizziness, nausea, lack of coordination, confusion, drowsiness, and with suffiently large doses, unconsciousness and death. The initial symptoms of methanol exposure are usually less severe than the symptoms resulting from the ingestion of a similar quantity of ethyl alcohol.

Once the initial symptoms have passed, a second set of symptoms arises 10–30 hours after the initial exposure to methanol: blurring or complete loss of vision, together with acidosis. These symptoms result from the accumulation of toxic levels of formate in the bloodstream, and may progress to death by respiratory failure. The ester derivatives of methanol do not share this toxicity.

Ethanol is sometimes denatured (adulterated), and thus made undrinkable, by the addition of methanol. The result is known as methylated spirit or "meths" (UK use). (The latter should not be confused with meth, a common abbreviation for methamphetamine.)

Pure methanol has been used in open wheel racing since the mid-1960s. Unlike petroleum fires, methanol fires can be extinguished with plain water (while methanol is lighter than water, they are miscible, and the addition of water will cause the fire to use its heat to boil the water). The decision was made shortly after the death of two drivers.

One concern with the addition of methanol to automotive fuels is highlighted by recent groundwater impacts from the fuel additive methyl tert-butyl ether (MTBE). Leaking underground gasoline storage tanks created MTBE plumes in groundwater that eventually adulterated well water. Methanol's high solubility in water raises concerns that similar well water contamination could arise from the widespread use of methanol as an automotive fuel.

Answer 3

It's what your body does with the methanol. It gets broken down to toxic substances, including formaldehyde, that attack the optic nerve and cause blindness.

See this for a bunch of info:
http://www.emedicine.com/NEURO/topic217.htm