Dow Beer Deaths (1966) [video]

In case you're wondering after the problem was corrected and the plant restarted Dow never recovered it's number one market share. The company did continue for another twenty years before discontinuing the Dow brand in 1997.

https://en.wikipedia.org/wiki/Dow_Breweries#:~:text=Canadian....

They were heavy drinkers - the effects of the heavy drinking may have masked the symptoms of the cobalt poisoning. It almost certainly made people take them less seriously, as evidenced by the laughing in the linked video.

… all patients were heavy drinkers… 30 out of those consuming more than six litres (12 pints) of beer per day. 6 litres!!!