Hi EcoMom,
Fumigation wouldn’t be a concern for me with any reliable manufacturer that knows to ship their cores on pallets that don’t need fumigation.
Yes some manufacturers add graphite both to help with the fire retardancy of latex and to customize the properties of the latex but all the latex you are likely to encounter would be tested for harmful substances and VOC’s by either Oeko-Tex or Eco-Institut (which are both reliable testing protocols) and I would consider any latex whether it was Dunlop or Talalay and made with natural rubber, synthetic rubber, or a blend of both to be safe yes (see post #2 here).
I would use a good mattress protector to prevent this from happening but if it did get soiled then it would need to be spot cleaned (see post #2 here).
Phoenix