Door Handles, Mine Problems, and Warfarin

Today I Learned:
1) Door handles are not, as a rule, found halfway up the door, which unfortunately makes them asymmetric to rotations around the horizontal axis through the plane of the door (so you can't flip them upside-down to switch from inward-facing to outward-facing or vice versa).

2) Arsenic and selenium are notoriously problematic metals for metal mines. Like many other heavy metals, arsenic and selenium are common toxic contaminants and have to be removed from the main ores. Unlike many other heavy metals, there isn't much of a market for arsenic or selenium, so it's not economical to extract them and sell them, so many mines have to dispose of them somehow.

3) Warfarin, a blood-thinning drug, is used as a mouse poison. It's laced into tasty food traps, and once eaten it causes the mice to hemmorage to death.