Vector effects of microplastics on organic pollutants: sorption-desorption and bioaccumulation kinetics

Microplastics (MPs) has their inherent detrimental effects on organism's physiology, additionally, they can sorb hydrophobic organic pollutants (OPs) from water, transport, and leach in the gut of aquatic biota, resulting enhanced bioaccumulation (vector effects). Thus, MPs mediated enhanced bioaccumulation can cause combined or synergistic toxicity in ingesters. Several laboratory and field studies have confirmed the ability of MPs to adsorb/absorb co-contaminants and suggested numbers of chemical and environmental factors affecting sorption kinetics. Besides, studies have also shown that these sorbed chemical can be leached in intestine primarily due to bile salts and governed by range of physico-chemical and biological factors, and resulted enhanced bioacumulation. However, some studies have declined the vector possibilities of MPs and emphasized multimode assimilation rather than single uptake pathway from MPs. Despite deliberate investigations, compilation and synthesis of existing reports on sorption-desorption process and subsequent vector or no-vector effects in biota are still lacking. Therefore, this review comprehends and synthesize existing data to provide summarized insights on pollutant binding, transport, leaching and consequent increased bioaccumulation. This review also compared the debate of vector vs no-vector reports and outlined a clear consensus.