Microplastics in aquaculture fish - investigating microplastic exposure in Nile Tilapia

Microplastics (MPs) in fish for consumption are considered a potential pathway for human exposure. While MPs have been widely detected in the digestive tracts of various fish species, their translocation to other organs and edible tissues remains poorly understood. The present study aimed to investigate the potential translocation of MPs in the liver, gonads, and fillet of adult Nile tilapia ( Oreochromis niloticus ) after 7 days of dietary exposure. Adult fish were fed with feed containing a mixture of four polymer types, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyamide 6 (PA6), in irregular shapes and sizes ranging from 10–350 μm. The polymers were quantified in the tissues using pyrolysis gas chromatography coupled with mass spectrometry (Py-GC-MS). Minimal MP accumulation was detected in liver and gonad samples, with MPs detected in fewer than 50% of samples. No MPs were detected in fillet tissue of either control or exposed fish, suggesting no translocation of MPs to edible muscle within the exposure period. Complementary analysis with micro-Fourier transform infrared spectroscopy (μ-FTIR) and optical microscopy on fecal matter revealed a high abundance of MPs, suggesting efficient excretion of ingested particles. These results demonstrated that short-term dietary exposure to MPs leads to negligible bioaccumulation in tilapia tissues, highlighting excretion as the dominant elimination pathway. This study provides novel evidence on the limited transfer of MPs for the analyzed size range to edible tissues in aquaculture species, with implications for food safety risk assessment. • Nile tilapia from RAS were fed MP-spiked feed for 7 days. • Py-GC-MS revealed low levels of MPs in liver and gonads but none in fillet tissues. • MPs in the 10-350 μm size range were primarily excreted via feces. • Complementary μ-FTIR and microscopy confirmed high MP loads in fecal matter. • Minimal risk of MP transfer to edible fish tissues under short-term exposure.