Secondary analysis of California regional water boards dataset: Morphological distribution of aquatic microplastics in San Francisco Bay and implications for liver disease pathogenesis

Microplastics (MPs) are widespread environmental pollutants, and there is growing evidence that they have potential impacts on human health. However, the role of particle morphology in mediating biological responses, particularly in liver disease, is still poorly understood. The aim of this study was to quantify the morphological distribution of MPs in aquatic environments and to assess their potential biological relevance based on experimental evidence.

A secondary analysis was conducted using a publicly available dataset of 19,874 MPs collected from surface waters of San Francisco Bay (2015–2020). Morphological, size, color, and spatial data were analyzed using R (v4.3.1). Temporal trends, spatial autocorrelation, and size-geometry relationships were assessed.

Fibers (49.8%) and fragments (40.3%) dominated the dataset. A significant temporal increase in fiber abundance was observed between 2015 and 2018 (p = 0.012). These fibers had extreme aspect ratios (> 50 : 1), and spatial clustering was identified in the Central Bay (p < 0.001).

These results suggest that microplastic morphology, particularly high-aspect-ratio fibers and irregular fragments, is a critical parameter in assessing environmental exposure and provides biological plausibility for oxidative stress and inflammatory pathways relevant to liver disease pathogenesis.