The offending substance in the liquor tragedies leading to blindness, etc. is

Methyl alcohol, also known as methanol, is the toxic substance responsible for liquor tragedies. While ethyl alcohol is the type of alcohol found in legal beverages, methyl alcohol is often found in illicit or adulterated liquor. When consumed, the human liver metabolizes methyl alcohol into formaldehyde and then into formic acid. Formic acid is highly toxic because it attacks the optic nerve, leading to permanent blindness. In higher doses, it causes metabolic acidosis and multi organ failure, which often results in death. Amyl and benzyl alcohols are used in industrial and pharmaceutical processes and are not typically associated with these specific mass poisoning incidents.