Accurate knowledge of atomic data is necessary for impurity transport studies that are based on simulations of experimental data. Measurements of spatial brightness profiles of Fe, Ni and Ge spectroscopic lines emitted by FTU ohmic plasmas have been compared with impurity transport simulation using assessed data for the ionisation S and recombination a rate coefficients. The F- to B-like charge states could not been simulated unless the relevant a/S ratios were multiplied by a factor of two. In FTU ohmic plasmas the mentioned charge states are located at intermediate radii, so that the core ionisation state is not much affected by the discussed uncertainty. For Mo, the F- to B-like charge states peak on axis if the central electron temperature Te is larger than about 3-4keV. It is important therefore to verify, after an assessement of the atomic data, if the mentioned a/S correction is necessary in this case too.