[MikeA]

Ahhh the beauty of man made products. I don't think the building of one cnc router with MDF will put you off the deep end. I would recommend using a decent dust mask, especially if you are more inclined to be effected by fine particulates but no need to go into panic mode. You will probably encounter just as many other harmfull products or byproducts in the construction of your router from grinding dust to the very paint you will spray to seal in the urea formaldehyde of the MDF. MDF is the preferred product because it is non directional, dense, consistent thickness and usually flat. Just a note in closing, urea formadehyde is present in most furniture, carpets, drapes, and even the glues used in plywood