  Observed ultraviolet (UV) colours of nearby disc galaxies show a reddening
relative to their expected intrinsic colours. Since the 2175 \AA bump found in
the Milky Way's dust extinction law blues the UV colours, it might suggest that
dust in nearby disc galaxies does not have the bump and that the Milky Way is
exceptional. However, this conclusion can be modified by the effect of
scatterings. If the scattering albedo decreases towards shorter wavelengths,
observable UV colours redden. An extensive comparison between observed UV
colours and those expected from radiative transfer simulations shows two types
of dust suitable for nearby disc galaxies: (1) dust with a bump and a smaller
albedo for a shorter wavelength (except for the bump range), and (2) dust
without any bump but with an almost constant albedo. If very small carbonaceous
grains responsible for the common unidentified infrared emission band are also
the bump carrier, the former dust is favorable.
