Association of faecal and urinary micro- and nanoplastics with markers of gut integrity and renal function

Micro and nanoplastics (MNPs) constitute an emerging environmental concern due to their persistence and ubiquity, but evidence on health effects remains limited. We explored the association between MNPs exposure and markers of gut integrity and renal function in a cross-sectional study in Barcelona (Spain). We enrolled 50 healthy adults who self-collected spot urine and stool samples. MNPs (0.7-20 μm) were measured using high-performance liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS). Calprotectin, zonulin, lysozyme, β-defensin-2 and lactoferrin were measured in stool samples via ELISA. Urea, creatinine and albumin were measured in urine through kinetic and immunoturbidimetric methods. Generalized linear models adjusting for potential confounders were performed to evaluate the association between MNP presence in biological samples and the mentioned biomarkers. Six MNP polymers were detected across 52% of stool and 48% of urine samples. Polyamide was the most frequently detected polymer in stool (34%) and urine samples (16%). Polypropylene (PP) detection in stool was negatively associated with calprotectin (Ratio of means-ROM [95%CI] = 0.52 [0.31-0.94]). In urine, the presence of any MNP polymer was positively associated with the albumin-creatinine ratio (uACR) (ROM [95%CI] = 2.18 [1.17-4.01]). Negative associations between PP in stool and lactoferrin, and polybutene-1 (PB1) in urine and uACR were observed, although these must be cautiously interpreted due to substantial lactoferrin measurement variability (lactoferrin undetected in 32% of samples) and a small number of PB1 detected samples (N = 5). Findings of this exploratory study suggest oral exposure to MNPs may be associated with renal function and gut integrity.