Tantalum is a biopersistent granular dust of a high density. Tantalum is not systemically distributed and accumulates only locally in the lungs. On the basis of current knowledge it cannot be estimated to what extent the high density of the tantalum particles has an influence on the burden of macrophages and the transport of the particles by the macrophages. Therefore, a MAK value in analogy to the biopersistent granular dusts cannot be established. Consequently, the respirable fraction of tantalum dust is classified in Carcinogen Category 3R and remains a candidate for Carcinogen Category 4.
Since no MAK value can be established, neither a peak limitation category nor a pregnancy risk group can be determined for tantalum. Tantalum is not designated with either “Sa” or “Sh” or “H”.