The dataset contains information on microplastics particle size and size fractions throughout a sediment core from Disko Bay, Greenland, collected in August 2015 and dated back to 1930. Each sediment layer (depth) corresponds to a Lead-210 year categorized as Pre-plastic Boom (before 1950) and Post-Plastic Boom (after 1950). The polymer type, major and minor dimensions and the score were obtained during µ-FTIR data processing through the software sIMple. Particle size were categorized as small (20 - 100 µm) and large (>100µm) and further divided intro size fractions ((1) 20-50µm, (2) 50-100µm, (3) 100-250µm, (4) 250-500µm, (5) ≥500µm). This datasets is complementary to https://doi.pangaea.de/10.1594/PANGAEA.972635, https://doi.pangaea.de/10.1594/PANGAEA.972713, and the limits of detection are in https://doi.pangaea.de/10.1594/PANGAEA.972709.