I can understand your fears ,although I find them to be somewhat unjustified . Extended research has been done on mice . https://hwbdocuments.env.nm.gov/Los Alamos National Labs/References/9125.PDF Some concerns are aroused regarding Niobium ,but it regards : http://journals.lww.com/spinejourna...um,_Niobium,_and_Aluminum_Levels_After.6.aspx Handling and using Niobium though, in the form of VC stems ,does not pose any real health risks : https://books.google.gr/books?id=nDhpLa1rl44C&pg=PT139&lpg=PT139&dq=niobium+health+effects&source=bl&ots=zNSjWPFChP&sig=FTaj84EfZ-5lU6Hec_bhScehwTg&hl=el&sa=X&ved=0ahUKEwjltLOP4vzXAhWSF-wKHT32CfMQ6AEISzAD#v=onepage&q=niobium health effects&f=false https://books.google.gr/books?id=vgHXTId8rnYC&pg=PA873&lpg=PA873&dq=niobium+health+effects&source=bl&ots=IY9hrphT-4&sig=Z3LTrBs_Qo7UqpNNvB5fPMIM1tM&hl=el&sa=X&ved=0ahUKEwjltLOP4vzXAhWSF-wKHT32CfMQ6AEITzAE#v=onepage&q=niobium health effects&f=false https://research.utdallas.edu/cleanroom/app/uploads/2014/12/niobium.pdf https://www.ganoksin.com/article/working-with-niobium/ ...as metallic niobium has a low order of toxicity due to poor absorption from stomach and intestines. Moreover ,there are plenty of peolple that have Niobium constantly inside their mouth and/or possibly to other " sensitive areas ": https://www.cda-adc.ca/jcda/vol-64/issue-11/803.html Fine Niobium dust particles ( as also dust particles of most materials ) are of some concern ,mainly about lung deposition ,but it applies only for miners of Niobium containing minerals and metal-workers working with Niobium (including myself ) and after a prolonged period of exposure to metallic Niobium dust or Niobium containing mineral dust . Niobium is hypoallergic and belongs to semi-precious metals . Beyond the fact that Niobium is considered as safe as Titanium* is , for those of you that still are not feeling totally safe with Nb , there's always Ti available . * http://www.espimetals.com/index.php/msds/296-Titanium Cheers.