Estimation of the uptake of polycyclic aromatic hydrocarbons desorbed from polyethylene microplastics in the digestive tract of the red seabream (Pagrus major) and mummichog (Fundulus heteroclitus)

The vector effects of microplastics (MPs) in natural marine environments and their contribution to polycyclic aromatic hydrocarbon (PAH) bioaccumulation in fish are still unknown. This study, therefore, aimed to evaluate the effects of MPs on carrying PAHs under conditions close to the actual marine environments. The PAH content sorbed onto MPs from seawater positively correlated with the octanol/water partition coefficient (log K) in both polyethylene and polystyrene MPs. The desorption rate constant (k) of PAHs sorbed onto MPs from seawater in the digestive tract was calculated using two marine teleost fish in an in vitro desorption experiment. A negative correlation was observed between the log K and k of the PAHs. The PAHs with larger log K and lower water solubility are easier to sorb onto MPs and less likely to desorb in the digestive tract of marine fish species. The estimation of PAH uptake into the fish body using the k of three selected PAHs (phenanthrene, pyrene, and chrysene) indicated that >95 % of the chemicals were uptaken from seawater via gills. It was presumed that there was an additional uptake of PAHs into the fish body (vector effect) due to desorption from MPs in the digestive tract when marine fish ingested MP that was sorbed and concentrated with PAHs. The degree of uptake was, however, much lower than that from seawater via gills. The vector effect of PAHs by MPs in the actual sea may be negligible, and the risk is presently considered to be low.