  We investigate the effect of strong, nonmagnetic impurities on
quasi-one-dimensional conventional and unconventional density waves (DW and
UDW). The conventional case remains unaffected similarly to s-wave
superconductors in the presence of weak, nonmagnetic impurities. The
thermodynamic properties of UDW were found to be identical to those of a d-wave
superconductor in the unitary limit. The real and imaginary part of the optical
conductivity is determined for electric fields applied in the perpendicular
directions. A new structure can be present corresponding to excitations from
the bound state at the Fermi energy to the gap maximum in addition to the usual
peak at 2\Delta. In the dc limit, universal electric conductivity is found.
