lordy - or urea formaldehyde, or rock wool with asbestos or vermiculite, or probably other deadly things as well... (Powdery kinda sounds like rock wool, fwiw.) You'll be doing good if they let you put it in the landfill instead of treating it as hazardous. I wouldn't chance it in my yard. Be sure to wear a dust mask when you're handling the bags.
Toxic Flame Retardants (PBDEs)
Why should I be concerned?
* PBDES are in blood, breast milk, and umbilical cord blood.
* Laboratory animals exposed to PBDEs show deficits in learning and memory.
* PBDEs affect thyroid levels in laboratory animals and in wildlife, and may cause birth defects.
A few years ago there were studies implicating fire retardant in furniture and carpeting, as being a cause of hyperthyroidism in cats, since they are small and close to the floor, the toxic levels shows up sooner than it would in an adult human.
Here's where it got very interesting. I am a Graves' disease patient and long time member of several large online forums. So, as you might guess we all started talking...I was shocked at how many of my fellow patients had new wall to wall carpet installed shortly before diagnosis. It takes a combination of such things to cause an autoimmune disease to surface, never just one thing. But there will generally be the 'straw that broke the camel's back'. The time when it just became too much for the body to deal with.
No.. I don't wear a tin foil hat.. but I'm willing to consider the fact that for some, the additional rise in PBDE levels in their homes could well have been a contributing factor. The studies are ongoing.
Not a healthy thing to have in the garden, that's for sure. For yourself and for future generations living there.
It was a great question. Thanks for asking. :) I'm sure others will find this interesting as well.
I was aware on a low level of concern, then a few years ago they did a Jean-Michel Cousteau special on PBS, here they explained they have found ... here...I found a link so I explain it correctly.
-- During a recent expedition, Jean-Michel Cousteau and his Ocean Futures Society team discovered an alarming fact: many populations of killer whales are contaminated with toxic, synthetic chemicals known as PBDEs, or flame retardants. --