Bleivergiftung
A modern version of the "purported dangers" claims that players suffered lead poisoning because armonicas were made of lead glass. However, there is no known scientific basis for the theory that merely touching lead glass can cause lead poisoning. Lead poisoning was common in the 18th and early 19th centuries for both armonica players and non-players alike; doctors prescribed lead compounds for a long list of ailments, and lead or lead oxide was used as a food preservative and in cookware and eating utensils. Trace amounts of lead that armonica players in Franklin's day received from their instruments would likely have been dwarfed by lead from other sources, such as the lead-content paint used to mark visual identification of the bowls to the players.