Is there any good literature on rubber mulch?  I want to use it underneath my kid's play structure.  I believe that the ability to reduce injuries due to falls is better than other materials, so from that standpoint, I like it.  However, I am seeing some stuff about wires inside, rubber leaching into the soil, potential fire hazard, etc.  The rubber mulch companies all say it is great of course, but what does the forum think?

thanks.