Here's a little known fact I uncovered while researching Victorian wallpaper--some of it has arsenic in it. Apparently arsenic was used in some of the inks, most specifically a sort of piercing green, which had copper arsenite in it. According to a book by Catherine Lynn, Wallpaper in America: from the seventeenth century to World War I, there were report of arsenic poisoning by wallpaper in the 1850's. It sounds to me a little like the lead poisoning problems I heard so much about when I was growing up. All right, I'm dating myself there.
Anyway, particles would be brushed off of this wallpaper accidentally and end up being ingested. This brings up an interesting question for those of us who tend to murder people in their books (that would be me). Arsenic seemed to be the poison of choice in the Victorian period. Could you blame the arsenic poisoning on the wallpaper?