Comparison of primary microplastics from Cartagena Bay and their toxicological evaluation using "Caenorhabditis elegans" as a biological model

Abstract

BACKGROUND AND AIM: Microplastic pollution in world oceans is an issue of great concern, since they cause damage to marine ecosystems. When ingested, they can exert toxicity, causing oxidative stress, cell damage and inflammation, compromising somatic processes such as fertility and reproduction among others, and affecting humans through the ingestion of marine contaminated food. METHODS: This research includes a statistical comparison and toxicity evaluation of black/tarred and degraded microplastic pellets present on Cartagena Bay beaches – Colombia, against industrial microplastics pellets. Samples of pellets were collected from Castillogrande and Bocagrande beaches, two urban beaches with a high presence of microplastic pollution coming from the nearby plastic industry. Sod-4, gpx-4, mtl- 2 fluorescent Caenorhabditis elegans strains were expose to microplastics pellets soxhlet extraction previously characterized by Gas Chromatography/Mass Spectrometry. Mortality and gene expression test were performed. Relationships were made considering the location and chemical composition of the collected pellets. The nematode was exposed during 24 h to whole black pellet extract solution and a 50% dilution extract. RESULTS:In terms of the lethality tests, a higher mortality of the nematode was obtained using the 50% dilution extract (45%) compared to the concentrated solution (20%). For the gene expression assay the genes with the highest exposure in all the dilutions were sod-4 and mtl-2 showing superoxide dismutase activity and metallothionein-2, respectively. The chemical characterization, showed a 30% of long-chain hydrocarbons, 14.8% of pesticides and 3.1% of hormones as the more relevant chemicals present in black pellets but not in industrial pellets. For degraded pellets, 45.5% of long-chain hydrocarbons, 10.9% of pesticides and 7.3% of acid anhydrides as relevant results. Significant differences were found, considering Dunnet analysis. CONCLUSIONS:The above results showed that microplastic pellets can adsorb contaminants present in water that can interfere with biological processes, contributing to the poor health of this touristic sector and nearby ecosystems. KEYWORDS: Microplastics, Toxicology, Chemical exposures