Polyisocyanurate anyone?

This rigid foam insulation...I read many posts on "green" forums that say that it is bad but do not expound their reasons. Anyone here have scientific reasons for their opinions? I want to use it to insulate the roof of my van.

From Wikipedia

poly - iso - cyan - urate

cyan is short for cyanide, and not healthy to breath.

The study evaluated the degree to which toxic products were released, looking at toxicity,
time-release profiles, and lethality of doses released, in a range of flaming, non-flaming,
and poorly ventilated fires, and concluded that PIR generally released
a considerably higher level of toxic products
than the other insulating materials studied (PIR > PUR > EPS > PHF; glass and stone wools also studied).[5]

Meaning, you can die from breathing the smoke, and not from smoke inhalation.

If memory serves, and that is an if, people were waking up dead in house fires where iso was burning.