Atomic-resolution diffraction imaging of biological particles using x-ray free-electron lasers (XFELs) at 1 A wavelength requires a detailed understanding of the photon-induced damage processes. We discuss how several aspects of existing continuum damage models can be tested during early operation of XFELs at lower x-ray energies in the range of 0.8-5 keV and low fluences, focusing particularly on macroscopic collective effects such as particle charging, expansion, and average ionization of nanospheres.