Prenatal exposure to microplastics and biomarkers of renal dysfunction in umbilical cord blood: Evidence from a birth cohort in China

Microplastics (MPs) are ubiquitous environmental contaminants with potential to cross biological barriers, including the placenta. Limited data exist on the human fetal exposure burden and associated health effects. This study investigates the presence and composition of MPs in placental tissue and evaluates their individual and combined (mixture) associations with renal biomarkers in umbilical cord blood, providing novel insights into early-life nephrotoxicity. A total of 1350 pregnant women were recruited from Shengjing Hospital of China Medical University (Shenyang, China) between 2022 and 2023. Placental samples were collected at delivery and analyzed for MPs using a high-resolution laser direct infrared (LD-IR) imaging system. Rigorous plastic-free protocols were employed. MPs were quantified and characterized by polymer type (e.g., polyvinyl chloride [PVC], polypropylene [PP], and polybutylene succinate [PBS]), with results expressed as number of particles per 10 g of placental tissue. Umbilical cord serum was analyzed for renal biomarkers: creatinine, cystatin C, blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL), and estimated glomerular filtration rate (eGFR). Mixture effects were assessed using Weighted Quantile Sum (WQS) regression and Bayesian Kernel Machine Regression (BKMR) models, adjusting for relevant covariates. MPs were detected in all placental samples, with a median total burden of 7 particles per 10 g tissue. WQS regression revealed a significant positive association between the MP mixture and elevated levels of creatinine (β = 0.089, p < 0.01) and cystatin C (β = 0.073, p = 0.015), indicating potential renal impairment. PVC was identified as the dominant contributor (WQS weight = 0.52), followed by PBS (0.31) and PP (0.17). BKMR analyses confirmed a positive nonlinear relationship between the overall MP mixture and creatinine and cystatin C levels, with posterior inclusion probabilities (PIPs) for PVC > 0.90. Marginal effect plots showed increasing biomarker levels with higher estimated MP exposure. For BUN, a moderate positive association with PVC was observed, whereas NGAL and eGFR exhibited weaker or borderline associations in the BKMR models, with confidence intervals overlapping the null, suggesting potential subclinical tubular stress and early reductions in filtration capacity. This study provides the first evidence that placental microplastic mixtures, particularly PVC, may be associated with altered neonatal renal function. These findings underscore the need for further research on prenatal MP exposure and its potential health consequences, especially regarding cumulative mixture effects.