"Considering all I've read about how nasty the dust from used media is, it practically sounds like toxic waste and I wondered if anyone took extra measures in it's disposal. Seemed like a reasonable question at the time."
Considering 'all you're read' your question is quite reasonable. What the guys are telling you is virtually all you've read is over-hyped BS dreamed up by overly sensitive, 'trust your government' type guys who wish to sound like safety experts and then it gets parroted on the web by Chicken Littles; meaning the comments aren't personal at you.
Toss your old media anyway you wish or scatter it on your lawn for mulch. It's such a low level 'poision' that as a land fill hazard it falls somewhere between old auto brake pads and empty cans of dog food, far below last Christmas' uneaten fruit cake.
So far as 'lead' being poison, of itself, I suppose that may be true but the "powdered" stuff is what gets into our blood stream, not solid lead. I have cast bullets, sinkers and fishing lures since '65 without issue but I have sense enough not to cast under a hood and I don't lick the gray smears off my fingers. Then an uncle of mine was wounded in WW2 and lived with the bullet lodged near his spine, we don't know if that's what got him but he died last November but the poor dude made it to age 92 so it must be a slow acting poison.