An excess consumption of methanol (option 1) can cause blindness and death. Methanol is highly toxic, and when ingested, it is metabolized in the body to formaldehyde and then further to formic acid, both of which are toxic compounds that can lead to severe health issues, including damage to the optic nerve, resulting in blindness, and in extreme cases, it can be fatal. Ethanol (option 2) is the type of alcohol found in alcoholic beverages and, while excessive consumption can have adverse effects, it is not as toxic as methanol. Methanal (option 3) and methanoic acid (option 4) are other names for formaldehyde and formic acid, respectively, and both can be harmful but are not typically ingested as they are.