Tokamak dust is an important contributor to the source term in ITER safety analyses. In this paper we present results of R&D at the INEEL and North Carolina State University to characterize tokamak dust. These results were used to set safety limits on dust for ITER. We present the results of analysis of particulate collected from three operating tokamaks: DIII-D at General Atomics, TFTR at Princeton Plasma Physics Laboratory, and Alcator C-MOD at Massachusetts Institute of Technology, and analysis of particulate produced in SIRENS, a disruption simulator at North Carolina State University. Analyses done include characterization of particulate to produce particle size distributions, chemical analysis, and measurement of effective surface area. The safety limits on dust in ITER have evolved during the EDA as more data have become available. The safety limits specified in NSSR-2 envelope the majority of the data, and provide conservatism to account for the uncertainty in extrapolation of the data to ITER.