  We analyse the photodisintegration of nuclei near the center of blazars, in
particular PKS 0528+134. We show that this process could explain the recent
observation of a high Al/Si ratio in a cloud on the line of sight of a distant
quasar and we calculate the effect of this gamma irradiation on the abundance
of deuterium, an isotope of the highest cosmological interest since it is
sensitive to the baryon density of the universe. The process has interesting
consequences and deserves to be inserted in a consistent scenario of the early
evolution of the universe.
