I was searching for ceramic knife and learned they can be made from Zirconia or Alumina. Some cheap ones could be from the latter because material is cheaper.
Isn't Aluminum Oxide poisonous to human body? I don't care much about the knife, but I do have a cheap manual cranking ceramic burr grinder for coffee. Those single use pepper grinder also has ceramic. Can't imagine they are made with quality in mind.
Should I worry?