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

The offending substance is methyl alcohol (methanol). Methanol causes optic nerve injury that can lead to blindness, and is specifically implicated in liquor-related poisoning incidents where adulterants are present [1]. Its toxicity stems from metabolic conversion to formaldehyde and formic acid, which produce severe metabolic acidosis and direct optic nerve toxicity, explaining the characteristic blurred vision and potential permanent blindness seen in outbreaks. Ethanol (ethyl alcohol) does not cause the same optic neuropathy, and other listed alcohols (amyl, benzyl) are not the classic cause of mass blindness from contaminated spirits. Clinically, blocking methanol metabolism (ethanol, fomepizole) and supportive care address these mechanisms.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > How do alcohols affect living beings? > p. 72