I was reading section 24 of Peebles "Principles of Physical Cosmology" where he analizes the impact of scattering by dust at redshifts z < 100 on the cosmic background radiation for an Einstein-deSitter universe. I was disappointed to find out that at the end of the subsection he concludes that this scattering may have changed the spectrum of the radiation, but that it obviously did not according to observations. I would have expected to have found a prediction that dust did actually not change the spectrum at high redshifts, or that such an effect did not leave an imprint in the spectrum greater than the scale of the current anisotropies. However, it seems to me that he is claiming that this depends strongly on the considered cosmological model for structure formation (see conclusions on page 597 after equation 24.95). Some discussion or some references on this would be welcome.