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Dust and associated depletion of heavy elements from the gas phase in HII regions can modify the emergent optical spectrum from that produced by a grain-free nebula. These changes result from a combination of effects including removal of gas-phase coolants, selective absorption of the ionizing continuum, and heating by grain photoelectrons. The influence of dust on the optical emission spectrum may be especially important in high-metallicity HII regions. Theoretical calculations illustrating the amplitude of these effects and their potential role in explaining some aspects of observed HII region properties will be presented.
