Microplastics can act as vector of the biocide triclosan exerting damage to freshwater microalgae

Despite the large number of recent studies on microplastics (MPs) and their ability to act as carriers of pollutants, the knowledge about the biological effects of MPs loaded with chemicals is scarce. The aim of this study was to evaluate the potential of MPs as vectors for the antimicrobial triclosan (TCS). For it, we tested low-density polyethylene (LDPE), polyamide (PA), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), polystyrene (PS) and the biodegradable polylactic acid (PLA). Thus, chemical analysis of sorption and desorption of TCS by these MPs was evaluated. The effect of TCS-loaded MPs to Anabaena sp. PCC7120, a cyanobacterium model of primary producers in freshwater ecosystems, was investigated. Chemical analyses showed different capacity of sorption depending on the MP type, which was related to some of their physicochemical properties. PA (104.7 μg/g), POM (57.4 μg/g) and LDPE (18.3 μg/g) were the polymers that sorbed the highest amounts of TCS. Glass transition temperature of polymers and their physicochemical interaction with TCS explained the extent of sorption. Significant decreases were found in growth, 22.3%, 94.6% and 81.0%, and chlorophyll a content, 58.4%, 95.0% and 89.6%, of Anabaena when exposed to TCS-loaded LDPE, PA and POM beads, respectively, which were the only MPs displaying significant sorption-desorption of TCS, implying that these MPs could act as vectors of TCS towards freshwater microalgae. This finding is of fundamental relevance as microalgae are at the base of the aquatic trophic chain and support growth of upper organisms.