I dunno --- maybe all that retardant makes the wildlife retarded?

Seriously, though, that is a good question.  It would be interesting to know exactly what chemicals are in that fire retardant, and how long they tend to persist in the environment.  Let's just hope that Roundup is not a constituent of the mix!  Knowing the perfidious and outright evil nature of many giant corporations nowadays, I wouldn't be surprised if they somehow managed to sneak some particularly nasty chemicals into such mixtures.