Effects of fibrous microplastics on the accumulation of tris(2,3-dibromopropyl) isocyanurate and behavior of zebrafish via water- and foodborne exposure routes.

Fibrous microplastics are abundant in water, and the additives on fibers could also be transported jointly, which is a combined pollution scenario prevalent in the environment. Organisms ingest microplastics directly from the environment or indirectly through trophic transfer. However, there is a dearth of available information on the uptake and effects of fibers and their additives. This study investigated the uptake and depuration of polyester microplastic fibers (MFs, 3600 items/L) by adult female zebrafish via waterborne and foodborne exposure routes and the effects on the fish behavior. Moreover, we used brominated flame-retardant tris(2,3-dibromopropyl) isocyanurate (TBC, 5 µg/L) as a representative plastic additive compound and explored MFs' effects on the accumulation of TBC in zebrafish. Results substantiated that the highest MF concentrations in zebrafish from waterborne exposure (12.00 ± 4.59 items/tissue) were approximately three times higher than foodborne exposure, suggesting waterborne exposure as the primary ingestion route. In addition, environmentally relevant MF concentrations did not affect TBC bioaccumulation via aqueous exposure. However, MFs could decrease TBC accumulation via foodborne exposure by ingesting contaminated D. magna, which was probably because MF co-exposure decreased the TBC burden in daphnids. MF exposure also considerably increased behavioral hyperactivity in zebrafish. Moved speed, travelled distance, and active swimming duration all increased when exposed to MFs-containing groups. This phenomenon remained apparent in the foodborne exposure experiment with a low MF concentration (0.67-6.33 items/tissue) in zebrafish. This study offers a deeper understanding of MF uptake and excretion in zebrafish and the accumulation of the co-existing pollutant. We also confirmed that waterborne and foodborne exposure may lead to abnormal fish behavior even at low in vivo MF burdens.