Dvice - A study from the Illinois Institute of Technology, has shown that some 3D printers can emit serious amounts of toxic nanoparticles. Exactly how many nanoparticles were emitted and how toxic they were varied wildly, depending on printer temperature and filament type, but all the emissions levels were high. The lowest emissions, for instance, were still on the order of 20 billion particles per minute.
Totally worth it.