May I take this opportunity to remind that the only drug known to be relatively safe is caffeine.
Fine powders are a fire safety and explosion risk, of course, especially in automated storage and processing environments....flour, non dairy creamer, aluminum powder, etc are great fun.
If there is any info to the contrary I would be very interested.
Fine water-soluble powders are absorbed quickly when inhaled, producing a very high peak concentration in the blood that supplies the heart. If it is enough to stop the heart from beating, you die, even if dose averaged over the whole body is reasonable.
People drown in water. Choke on water. There's water poisoning if you have too much of it.