This is actually a pretty interesting thing... basically the government mandated an increase in methanol (poisonous) content in industrial ethanol (not particularly poisonous, at least at reasonable volume) which was often stolen and half assedly filtered and sold as liquor. So people drank too much and ended up blind/dead. This still happens in modern times since methyl and ethyl alcohols are similar.

If you want to read more:
https://slate.com/technology/2010/02...ohibition.html