Playsand and wood stove ashes, here. They would rather be out excavating around the supports of the front deck (favorite hideout), but the run bath gets used.
Playsand and Food grade DE in a large rubber feeder. Food grade DE is fine and has been used for many years, and I have noticed that many people on BYC use it without mishap. Just don't mistakenly buy the kind that is used in swimming pools which is not food safe and therefore not safe for chickens as well.
I'm sure thats right, sand is natural, if there is no dust, inhalation should not be an issue. I would use it as well, I like the wood ash play sand idea when properly controlled. De is also natural, it is mined from the earth and dried to zero % moisture.
Remember for every action theres a reaction not always of equal force.
Mine dust bath in their coop in the pine shavings mixed with a little DE. Since they will usually dust bathe to keep bugs off of them the DE will help with that. They LOVE the deep litter in their coops. ALthough it's quite dusty in there when I have five at a time taking a dust bath!