Detection and quantification of microplastics in cerumen

Microplastics (MPs) are a growing concern due to their pervasive environmental presence and their potential impact on environmental and human exposure. Given evidence of systemic MP presence in human tissues and fluids, and the ear canal's environmental exposure, this novel study aimed to identify these particles in human cerumen. Cerumen was collected from the proximal ear canal to minimize potential airborne contamination.

Cerumen samples were prospectively collected from 12 adult patients (23 patient-derived samples) and three control water samples, following ethical approval and consent. Samples were extracted using sterile instruments, stored in glass, diluted, and filtered through 0.22 μm cellulosic membranes. Microplastics were identified and measured morphologically using a 10× laboratory microscope with digital image processing; however, chemical confirmation of polymer type was beyond the scope of this initial study. Descriptive statistics were employed for analysis.

Among the 12 adult patients (23 patient-derived samples), microplastic particles were detected in 10 (83.3%, patient level detection rate). A cumulative total of 31 individual MPs were identified across the 23 patient-derived cerumen samples analyzed (comprising 29 detected and two instances of zero particle detection), ranging significantly in size from 16 μm to 930 μm and displaying various colors. Water control samples contained seven particles (3-46 μm), showing a clear size disparity from cerumen-borne particles.

This study provides solid evidence of microplastic presence in human cerumen, suggesting a novel potential route of elimination from the human body. The high detection rate among patients and distinct characteristics of cerumen-borne MPs compared to controls imply genuine human accumulation rather than procedural contamination. Cerumen highlights a promising potential noninvasive bioindicator for assessing microplastic exposure. Further research in larger populations is essential to confirm these findings, elucidate mechanisms, identify polymer types, and explore potential health implications.