  The ionizing spectral energy distribution of quasars is known to exhibit a
steepening of the distribution short-ward of 1050\AA. It has been assumed that
this change of power-law index from -1 to -2 is intrinsic to the quasars. We
study an alternative interpretation, in which a tenuous absorption screen is
responsible for the change of index. A successful spectral fit is obtained
using a total hydrogen density distribution decreasing with redshift as $\sim
(1+z)^{\xi}$ with $\xi$ of the order -3.5 if we suppose that the ionization
state of the intervening gas is controlled by the line-of-sight quasar. This
interpretation is not compatible, however, with the relative weakness of the
observed quasar intensities with respect to that of the local background
metagalactic radiation. Therefore, our interpretation in its present form
cannot be sustained.
