[panpanna]

PCB Mills create a lot of fiber glass powder. That thing is not healthy to inhale.

You can buy PCB of other materials such as compressed papper (F2?) but they are not easy to get hold off.

[madengr]

My mill has the cutter fully surrounded by a vacuum manifold, and the vacuum itself is bag and HEPA filtered.

The compressed paper PCBs have horrible properties. The RF laminated all have specific properties for electrical performance; dielectric constant, low loss tangent, low surface roughness, homogeneity, controller thermal expansion, thermal conductivity.