The question is: What makes people think that homebrew is a risk?
In prohibition, the idea of making one’s liquor was well-known. Of course, people brewed beer, but items like moonshine or liquor were more well-known than beer. The moonshine, as well as the liquor (also wine), contain methional.
If an individual is exposed to methional in excess, it’s known as formaldehyde poisoning. Formaldehyde poisoning could cause blindness as well as other complications. A high concentration of methional was a typical issue during prohibition since amateur brewery owners didn’t distill moonshine and liquor correctly.
Beer is different, however. It’s nearly impossible for your beverage to have a methional level that could cause problems. You’d have to add a lot of ruby alcohol into your beverage for it to contain the methional level that is dangerous in it.
There are indeed no known toxic substances that could survive within the beer. The production of methyl alcohol that is toxic is almost impossible. But this doesn’t mean that home-brewed beer is not susceptible to contamination by the surrounding environment that surrounds the brewery.

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