This is a custom process, therefore each piece has its own peculiarities. It depends on the complexity of the sculpture, computer time, and material used. It took about 2 weeks. This applies if there is an overlapping shape or undercut, and can also be true depending on how the object is scanned, and which surfaces are critical to the finished product. The artist is shown a computer printout before cutting, so you can see what areas will need to be reworked.
Toxicity is a complex subject.
Water is toxic if you breath it. Smoke from burning foam is toxic. As supplied, foams we use can be safely carved and sanded without risk. Reasonable safety precautions are recommended for comfort and protection from nuisance dust. These materials do not require respirators for carving.