Probably not, at least as a proportion of the population, given that by the 1930s the entire reading public of the USA and UK knew about arsenic eaters. Probably most famously in Strong Poison by Dorothy L. Sayers (1930)[0].
Also taught in schools across the British Empire in the early 1900s would have been the stories of King Mithridates[1], or of the Arsenic eaters of Styria (see this 1869 Scientific American Article [2]).
Isn't it sad that an article written in the 1860d contains more interesting content and actual data than even the average article or op ed price today?
Probably most famously in "The Princess Bride" (not arsenic, though).