Ok this is what I dug up. The Magic Eraser is made of something called "melamine foam". Melamine is a resin that is used in the automotive and construction industries as a sound barrier, and also used as a fire retardant. It is further used to add strength to laminate counters and some dinnerware apparently. (reference
) The chemical make up is a formaldehyde-melamine-sodium bisulfite copolymer, meaning to the best of my understanding that these things combine to make up the melamine foam. It's my understanding that once these are combined the melamine foam is a completely new product rather than a fruit salad of the different pieces. (chem make-up reference here
) Finally, it seems that this foam is made up of fine abrasive pieces that, when combined with the porous texture of the foam, works to scrub off the dirt while trapping it in the pores. Because of the way it's formulated, this does cause it to break down easily. (reference
As for toxicity, all I could really find were references to how it reduces toxic emissions during fires and how when melamine (non-foam) was added to dog food ingredients it caused a lot of pet illnesses and deaths. A better site I found is here
Don't know if this helped or made it more confusing! LOL!