Uptake, bioaccumulation, biodistribution and depuration of polystyrene nanoplastics in zebrafish (Danio rerio)

Plastic nanoparticles formed from both daily use of plastics and their wastes have emerged as a potential health and environmental hazard. It is necessary to study the biological process of nanoplastics in ecological risk assessment. To address this concern, we quantitatively investigated the accumulation and depuration of polystyrene nanoplastics (PSNs) in the tissues of zebrafish after the aquatic exposure using a quantitative method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Via the PSNs-spiked freshwater, zebrafish were exposed to three different concentrations of PSNs for 30 days, followed by 16 days of depuration. The results showed that the amounts of PSNs accumulated in zebrafish tissues were in the following order: intestine > liver > gill > muscle > brain. The uptake and depuration of PSNs in zebrafish both followed pseudo-firstorder kinetics. It was revealed that the bioaccumulation was concentration, tissue and time dependent. When the PSNs concentration is low, the steady state might take longer time (or not occur) than that of a high concentration. After 16 days of depuration, there were still some PSNs present in the tissues particularly in the brain, where it might take 70 days or more to remove 75 % of PSNs. Overall, this work offers important knowledge on the bioaccumulation of PSNs, which may be useful for future studies into the health hazards of PSNs in aquatic environments.