Southern Africa, northeast Iran, and northern China have unusually high incidences of esophageal cancer, and several studies have indicated that consumption of flour contaminated with canaryseed "hairs" (spicules) may be a contributor. Another study found that mice fed traditional varieties of canaryseed developed tumors around their mouths and noses, the areas that most frequently came into contact with the silica hairs. Several studies have called out physical similarities between silica spicules and asbestos fibers. It's possible that the sharp, needle-like shape of the silica spicules on traditional canaryseed hulls may contribute to cell damage in the throat that may lead to cancer. But before you start to worry about canaryseeed, please note that the "hairless" (glabrous) varieties do not have these spicules at all.