The poisonings have occurred over the past six weeks in the city of Tabriz, where just last month, another 72 people reportedly were hospitalized after drinking impure homemade vodka. In October, Iranian media outlet IRNA revealed that over a matter of days, 42 people across the country died from drinking tainted booze and more than 350 were sickened.
Iranian Muslims have been banned from drinking alcohol since 1979, though non-Muslims are legally allowed to produce and consume small amounts. Drinking at home, however, is widespread among Iran's upper and middle classes, with the hooch provided by bootleggers or brewed at home.
It's the home-brewed hard stuff that's the problem. Methanol, a type of alcohol related to the ethanol that people can drink and process as a toxin, is a much more dangerous compound, but as it occurs naturally in the distilling process, it must be removed from alcoholic products before they're consumed. This is done easily by large, well-regulated productions, but less easily at home. And because methanol is cheap and will indeed get people drunk, unscrupulous manufacturers will sometimes add it to their brews, though as little as two ounces can be fatal to adults. Methanol metabolizes in the body into formic acid, which is highly toxic, and human optic nerves are particularly sensitive to the stuff, which is why methanol poisoning can result in blindness.
Methanol poisoning by drinking impure alcohol or alcoholic products not meant for consumption is not uncommon. India has seen more than 250 deaths already this year from two batches of bad booze, and parts of Mexico's most popular tourist zones have come under scrutiny recently for serving visitors dodgy drinks either accidentally or with the intention of rapidly intoxicating and robbing them.