While the advice about dust protection is very valid and should be followed thoroughly, it should be said that there are no spores in spalted wood (at least, no spores from the fungus that caused the spalting) Spores are entirely a product of the fungus fruit body, the actual mushroom, toadstool (or mainly, though by no means always, in the case of wood) bracket fungus. The spores are produced in the gills, or in some fungi, small holes in a sponge like mass where gills would otherwise be found, any fungus produces millions of these from the fruit body, usually within a few days or a week or so after growing to maturity, the spores are incredibly tiny, requiring a microscope to see them. Hence they are very light in weight and are wind and air distributed, at any time then, the air you are actually breathing now is quite likely to have spores from fungus anywhere in the world, the spores are carried enormous distances and remain viable for long periods, however, they require very specific conditions before they can begin to grow into a fungi again, hence, despite the large distribution of the spores, the fungi remain roughly confined to those areas and climates that suit each particular type.
The black lines and white areas as well as any colours in spalted wood are caused by different fungi establishing a boundary from a neighboring fungal growth, these growths are in fact the true fungus, called the mycelium, a sort of root or mesh like structure that is actively breaking down the wood and using it as an energy source, the fruit bodys, like any fruit, are the means of reproducing, and are the external and visible part of the organism. Thus, no spores are in the wood itself.
However, the caveat about dust is still totally relevant.
this video by Seri Robinson has much interesting info on spalting too.
