Everyday Consumer Chemicals and Immune Aging: PFAS and Phthalates in US Adults

Overview

An overwhelming 98% of US individuals show detectable levels of Per- and Polyfluoroalkyl Substances (PFAS) and phthalates—ubiquitous environmental chemicals found in everyday consumer products, with poorly understood health implications. This project aims to examine the relationship between PFAS/phthalates and aging of the immune system in US adults, utilizing two cycles of nationally representative NHANES data (2015-2018). Immune aging was defined as a novel composite (normal, mild, moderate, and severe) using absolute lymphocyte count, neutrophil-to-lymphocyte ratio, and high sensitivity C-reactive protein levels. Survey-weighted multinomial logistic regression was used to assess 16 urinary phthalates and four serum PFAS exposures—all log-transformed prior to analysis—while adjusting for a minimal set of potential confounders identified through a Directed Acyclic Graph. Bayesian Kernel Machine Regression (BKMR) was explored to identify mixture effects. A total of 2,971 participants were included, of which 34%, 56%, and 2% showed mild, moderate, and severe immune aging, respectively. The correlation coefficients for PFAS and phthalates ranged from -0.1 to 0.1. Four phthalates were significantly associated with relative risk ratios ranging from 1.20-1.25 for mild and 1.37-1.53 for severe aging, compared with the normal group, per doubling in exposure. Six PFAS were negatively associated with mild, moderate, and severe immune aging. The Posterior Inclusion Probabilities of 0.85-1.00 (phthalates), and 0.04-0.97 (PFAS) from BKMR indicate potential mixture effects. These findings suggest that exposure to phthalates, commonly found in personal care products, may accelerate aging of the immune system, contributing to increased susceptibility to infections and impaired detection of malignancies.

Competition history

• CSEF 2026 Environmental Engineering (Track 2) (Junior Division) · Entry J-12-01

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