What's best to give chickens to dust bath in?

[SilkieNation]

I think the jury is out on DE - some people swear by it others, like myself won't use it. The packaging has all sorts of warnings about not breathing it and wearing a mask when using it because it contains crystalline silica, which is harmful to human respiratory systems. I've read in many places that it can be very harmful if breathed (not chemically, but because of the silica and the micro damage it causes to respiratory tissue). But, I just did a quick query and found this from the state of Oregon claiming it's not that harmful. So, who knows. Do make sure it food grade DE though.

http://www.deq.state.or.us/er/docs/LowerBridge/DiatomaceousEarthFactSheet.pdf (sorry couldn't get the link to go live)