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Infrared dust mass and associated measurements are used to study the properties of the ISM (structure, radiation field, grain composition, total gas mass) in many astrophysical objects, including galaxies. It is often assumed that the far-IR dust grain properties are well described by a single emissivity law that does not depend on environment. I will discuss an investigation using the HERITAGE Herschel Key Project far-IR/submm observations of the Magellanic Clouds that indicate there are wavelength dependent variations in the dust emissivity law with environment. Then, I will show that an independent tracer of the dust column and grain size is possible using measurements of a large number of stars in M31 from the PHAT Hubble Multi-Cycle Program. Combining the PHAT measurements with Herschel far-IR/submm observations of M31 gives strong evidence that the overall dust emissivity is also dependent on environment. The combination of these two investigations gives strong evidence that far-IR/submm dust emissivity is varying significantly with environment. These results provide constrains on dust grain properties and indicate more realistic dust models should be used in interpreting far-IR/submm observations of galaxies.