  There is growing interest in quantum-spacetime models in which small
departures from Lorentz symmetry are governed by the Planck scale. In
particular, several studies have considered the possibility that these small
violations of Lorentz symmetry may affect various astrophysical observations,
such as the evaluation of the GZK limit for cosmic rays, the interaction of TeV
photons with the Far Infrared Background and the arrival time of photons with
different energies from cosmological sources. We show that the same
Planck-scale departures from Lorentz symmetry that lead to a modification of
the GZK limit which would be consistent with the observations reported by
AGASA, also have significant implications for the evaluation of the
Bahcall-Waxman bound on the flux of high-energy neutrinos produced by
photo-meson interactions in sources of size not much larger than the proton
photo-meson mean free path.
