Abstract: A method for quantifying microplastic exposure in a subject includes receiving a blood sample and measuring, using liquid chromatography-mass spectrometry, concentrations of a plurality of non-endogenous chemical biomarkers in the blood sample, wherein each biomarker is associated with at least one microplastic polymer type. The method may include comparing the measured concentrations against baseline contamination levels derived from control samples. Biomarker concentrations attributable to in-vivo microplastic exposure may be identified based at least in part on the comparing. An exposure assessment for the subject may be generated based at least in part on the biomarker concentrations, wherein the exposure assessment indicates exposure levels for one or more microplastic polymer types. The exposure levels may be categorized relative to a population reference dataset and may be mapped to likely sources of microplastic exposure.