Insoluble microparticle concentrations and grain-size distributions are measured with an Elzone 280PC particle counter in a Class 100 clean room at the University of New Hampshire. The Elzone uses a 30 um orifice to measure microparticle concentrations in 64 logarithmically- divided channels from 0.65 um to 11 um and calculates a grain-size distribution as an equivalent spherical diameter. Mass values were calculated assuming an average density of 2.65 g/cm3. Mean grain size is based on the number of particles. We have also used mean grain size based on mass as discussed in Zielinski and Mershon [in press]. Beta values are the slope of the best-fit line of the grain-size distribution on a logarithmic scale by channel measured with lower beta values reflecting an overall coarser grain-size distribution and a higher beta value reflecting an overall finer grain-size distribution. Because some channels can have zero counts in them, the beta value may not be a reliable proxy of the overall coarseness/fineness of a sample. We do not use it in our interpretation of the insoluble microparticle record, but it is provided here because it has been used in the past by other ice core investigators.