The study on the accumulation effect of aging polylactic acid microplastics on chromium in the marine medaka (oryzias melastigma)

The toxic effects of polylactic acid (PLA) microplastics (MPs) on aquatic organisms have garnered widespread attention. However, there is insufficient research on the impact of aged PLA-MPs on the accumulation of heavy metals within organisms. Therefore, this study focused on UV-aged PLA-MPs, utilizing inductively coupled plasma mass spectrometry to determine the accumulation of chromium in marine medaka following joint exposure to original and aged PLA-MPs with chromium. The results indicated that the color of the aged PLA changed from milky white to yellow, the surface of the PLA became rougher with noticeable grooves and protrusions, and there was a significant increase in oxygen-containing functional groups, primarily carbonyl (C=O) and hydroxyl (O-H) groups. Aged PLA significantly increased the Cr content in the marine medaka, with Cr primarily accumulating in the fish's visceral mass. Additionally, after joint exposure to aged PLA and heavy metals, the PLA content within the marine medaka was significantly higher than that of the original PLA. The findings of this study suggest that aged PLA enhances the accumulation effect of chromium in the medaka. Compared to original PLA, the joint exposure to aged PLA and heavy metals may exhibit greater toxicity.