Don't mean to suggest that there is any reason to worry, but I do have some concerns about this. I just discovered that my chickens have been eating the blue foam insulation that's on the outside of my house's foundation for sometime now. The kind of insulation I have is Extruded Polystyrene, made by Dow. I'm not particularly worried about the foam itself, but in doing a bit of internet research I found that all of these exterior rigid foam insulation products are made with a brominated flame retardant called HBCD (hexabromocyclododecane). HBCD is a known health hazard to humans, according the the EPA: http://www.epa.gov/hpvis/rbp/HBCD.3194556.Web.RBP.31308.pdf
Now, I DO NOT KNOW if, when chickens eat this stuff, it winds up in their meat or eggs. But I certainly intend to find out before I slaughter any chickens or start eating any eggs (my hens haven't started laying yet.)
I've got a call into my local ag extension office and will post here if I learn anything new. If anyone else out there has researched this issue and has any solid information, please post here also.