  We place new constraints on sources of ionizing and resonance radiation at
the epoch of the recombination process using the recent CMB temperature and
polarization spectra coming from WMAP. We find that non-standard recombination
scenarios are still consistent with the current data. In light of this we study
the impact that such models can have on the determination of several
cosmological parameters. In particular, the constraints on curvature and baryon
density appear to be weakly affected by a modified recombination scheme.
However, it may affect the current WMAP constraints on inflationary parameters
like the spectral index and its running. Physically motivated models, like
those based on primordial black hole or super heavy dark matter decay, are able
to provide a good fit to the current data. Future observations in both
temperature and polarization will be needed to more stringently test these
models.
