Uptake, Whole-Body Distribution, and Depuration of Nanoplastics by the Scallop <i>Pecten maximus</i> at Environmentally Realistic Concentrations

TLDR

Previous nanoplastic studies used unrealistically high concentrations, highlighting analytical challenges and the need for environmentally realistic approaches, and suggesting that particle composition may affect uptake and distribution. The study exposes scallops to 14C‑labeled nanopolystyrene at environmentally relevant concentrations (<15 µg L⁻¹) to assess uptake and biokinetics. Using pulse exposures of 14C‑labeled 24 nm and 250 nm nanopolystyrene, the authors measured uptake, distribution, and depuration in scallop tissues. Uptake was rapid and size‑dependent, with 24 nm particles dispersing systemically and 250 nm particles accumulating in the intestine; both sizes were depurated quickly (24 nm gone by 14 days, 250 nm by 48 days), indicating that particle size governs biokinetics and that equilibrium would require ~300 days of exposure yet remain below 2.7 mg g⁻¹.

Abstract

Previous studies of uptake and effects of nanoplastics by marine organisms have been conducted at what may be unrealistically high concentrations. This is a consequence of the analytical challenges in tracking plastic particles in organisms at environmentally relevant concentrations and highlights the need for new approaches. Here, we present pulse exposures of 14C-radiolabeled nanopolystyrene to a commercially important mollusk, Pecten maximus, at what have been predicted to be environmentally relevant concentrations (<15 μg L-1). Uptake was rapid and was greater for 24 nm than for 250 nm particles. After 6 h, autoradiography showed accumulation of 250 nm nanoplastics in the intestine, while 24 nm particles were dispersed throughout the whole-body, possibly indicating some translocation across epithelial membranes. However, depuration was also relatively rapid for both sizes; 24 nm particles were no longer detectable after 14 days, although some 250 nm particles were still detectable after 48 days. Particle size thus apparently influenced the biokinetics and suggests a need for chronic exposure studies. Modeling extrapolations indicated that it could take 300 days of continued environmental exposure for uptake to reach equilibrium in scallop body tissues although the concentrations would still below 2.7 mg g-1. Comparison with previous work in which scallops were exposed to nonplastic (silver) nanomaterials of similar size (20 nm), suggests that nanoparticle composition may also influence the uptake tissue distributions somewhat.