Novel Applications of Item Response Theory in Environmental Health: Quantifying Cumulative Exposome Burden Scores for Harmonization and Report-Back

Abstract: Summary scores of cumulative chemical exposure burden are increasingly used in environmental health research. These summary scores can be useful for risk assessment, harmonization across studies and report-back to study participants. I will discuss how psychometric approaches, in particular item response theory (IRT), can be used to create exposome burden scores and to set a common exposure burden scale across studies, even if they do not measure the exact same set of chemicals. I will also discuss how we can borrow approaches in the IRT literature for differential item functioning (DIF) detection to increase the precision of summary scores. These approaches, including mixture IRT and regularized DIF, can be used to account for exposure source heterogeneity and regrettable substitution over time, in which industry may phase-out the use of some chemicals and introduce similar replacements. Applications will focus on PFAS forever chemicals and plasticizers. I will also discuss the creation of exposure burden calculators, such as the U.S. PFAS Exposure Burden Calculator, to enable a common exposure scale for cross-study harmonization.