Small interstellar dust grains radiate from wavelengths of a few
  microns to beyond 25 microns.  We have previously  studied the
  effects of progressively decreasing radiation fields on dust in
  interstellar clouds.  This study extends that work into high
  radiation field environments.  Our IRAS survey and LRS data
  from neutral high radiation environments show broad band
  featureless emission across the IRAS LRS spectrometer
  passband.  12 and 25 micron survey emission simultaneously
  decline as radiation density increases, suggesting destruction
  of carriers in both bands.  Deep inside high radiation
  environments, IRAS survey and spectral data may show
  graybody emission.  Our data and models raise fundamental
  questions about dust in high radiation field regimes.  The data
  suggest that small dust grains may not emit by the same
  process as radiation density increases.  These data suggest
  destruction of the carriers correlated with radiation density, but
  not with radiation hardness.  Ionizing radiation may dissociate
  molecular but not solid state carriers.  Reduction of
  progressively larger carriers with increasing radiation density is
  predicted by solid state runaway sublimation.  Neither fit the
  data well.  In very high radiation density environments IRAS
  LRS spectra show emission beginning at 14 microns peaking
  near 20 microns which may be gray body emission.  Data at
  longer wavelengths resolve the issue.  Solid state or molecular,
  non-thermal continuum emission, grey-body emission, and
  spectral structure, these fundamental issues on the nature of
  small dust grains may be uniquely answered with ISO.  Each
  appears spatially restricted.  Our present data and models
  reveal locations to address points.