Not that ethanol isn't also neurotoxic (to a much lesser degree), but bootleg moonshines common during prohibition often contained trace amounts of methanol, the number of people irreversibly injured by methanol poisoning greatly exceeded the number who died.
By 1926, according to Prohibition, by Edward Behr, 750 New Yorkers perished from such poisoning and hundreds of thousands more suffered irreversible injuries including blindness and paralysis. [0]
This was likely the cause of the vast majority of methanol poisonings during the prohibition. You have to use exotic, hard to break down carbohydrates in your beer, wine, or mash (the pre-distillation fermented product), like tree bark, to end up with significant quantities of methanol.
Most of the methanol poisonings were from poorly "re"natured fuel alcohol.
Yeah, industrial alcohols were (and still are) "denatured" with additives to make them toxic or unpalatable and industrial alcohol was often used as a precursor for bootleg spirits during prohibition. I think modern denaturants lean more towards unpalatable than toxic.
No, I meant methanol. It's an easy contaminant to produce through improper distillation practice, and the most common of several contaminants which produced unfortunate outcomes among drinkers of illegal liquor during prohibition.
Methanol specifically is produced during the distillation process. The methanol vapors and ethanol vapors reside next to each other in the distillation column, making it a common impurity that is brought over in the distillation process. Great care needs to be taken to avoid collecting the methanol.
This simple fact is the greatest argument for distillation having much higher legal barriers than the simple brewing involved in beer/wine/mead.
Distilling doesn't produce jack-diddly-squat. It just concentrates. Methanol is a side effect of the fermentation process, and only common with exotic carbohydrates. In a normal beer, wine, or wash, you'll find less methanol than in your morning glass of orange juice.
I don't know what "exotic" means in the context of moonshine, but I've known some mountain men who weren't clever or careful about it and would ferment damn near anything - which is why I've drunk moonshine exactly once, and intend that to remain the case for the balance of my life.
Poking around the web, it seems as if making liquor at home has become popular among booze nerds. That's great and all, but I wouldn't call it moonshine, and I'd be very hesitant about how much I reasoned based on what well-informed people do today about the practices of a century ago, or indeed about the practices of today among those for whom making moonshine is more a family tradition than a hobby.
If it vaguely, and I mean vaguely resembles starch or sugar, you're not getting methanol. It's substantially harder to convert long polysacharides into ethanol/methanol than it is to convert starches and simple sugars, to the point that the less informed a person is, in the off chance they succeeded in making alcohol, the less likely there's going to be substantial methanol levels.
The vast majority of moonshine stills were just churning out unaged corn whiskey from animal feed corn. There is no risk of methanol poisoning in that scenario.
Speaking technically, methanol isn't produced during distillation, it's concentrated. Since it boils at a lower point than ethanol, it disproportionately comes out in the "heads" of a distillation run. The source wine/beer/mash already has all the methanol in it, it's just it's not a problem when present in the small quantities in a non-distilled drink, alongside with a much greater amount of ethanol. (Ethanol can actually act as an antidote to methanol since your body processes it first and can then excrete much of the methanol unmetabolized)
The risk of methanol poisoning in moonshine is grossly overrated. Simply put, you have to do some stupid shit to end up with dangerous amounts of methanol. The methanol content in a beer, wine, or mash precursor to liquor production will be absolutely trivial, unless you are are doing something ridiculous like trying to make liquor from tree bark (the Greeks have a drink like this, it's heavily warned against in home distilling circles).
So why was methanol poisoning common during the Prohibition? Renatured fuel alcohol. To stop people from drinking fuel ethanol, the government poisoned the supply with methanol. People tried to come up with jerry-rigged solutions to remove the methanol, and more often than not failed. Some less scrupulous experimenters sold their results anyway, where it worked its way into the black market supply chain.
