Comment by jpeloquin | Hacker News Reader

Comment by jpeloquin | Hacker News Reader

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From [1]: "In human metabolism of methanol, given its physical and chemical properties, high skin absorption is expected. Methanol penetration is predicted at 2.0 mg/cm2/h (logP = −0.77). Skin absorption of methanol vapor is another primary exposure route in terms of respiratory exposure."

I had a hard time finding dermal exposure thresholds for adverse effects. Oral intakes associated with severe acute effects were easier to find and could be used to estimate the effects of dermal intake. The smallest systemic oral intake threshold I saw was 3–11 g: "An oral intake of 3.16–11.85 g/person of pure methanol could cause blindness."

From those values, I think you're probably right; at least, death or blindness from dermal exposure to methanol seems unlikely. But the thresholds for less severe symptoms and the relevant intake thresholds for symptoms from chronic exposure are unclear to me.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625597/

Hand surface area is often given as 1% of body surface area (1.5-2 m^2), i.e. 150-200 cm^2, unclear if one or both hands but I assume one. I've also found claims of 400 cm^2 for one hand.

Methanol penetration is predicted at 2.0 mg/cm2/h" would imply that assuming two hands of 800 cm^2 total, exposed to methanol "hand sanitizer" for 5 minutes, would absorb 133 mg of methanol.

I think the skin absorption issue is a red herring and the real issue is that people keep drinking it.

As a Boy Scout in the 90s we used methanol stoves (Trangia) and lanterns, in the UK it’s untaxed alcohol.

Spills were common, as was pouring it in your hand or boot, igniting it and running around in the dark. I’m sure we came into contact with way more than you’d use as hand sanitizer—-and I never heard of anyone with ill effects.

Thank you, that's helpful!

Yeah, this confirms my belief that infrequent dermal exposure to methanol is not a particularly pressing health concern. It sounds like very little gets through the skin, and the main concerns are skin irritation, which you can get with ethanol anyhow.

I'd be fine using a 90% ethanol 10% methanol hand sanitizer the way I currently use it -- spraying my hands and rubbing them maybe 4 times per day either outdoors or in a well ventilated house, and not horking the fumes.

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