Influence of microplastics on the toxicity and environmental fate of selected antidepressants

According to the European Chemicals Agency, microplastics are very small particles composed of mixtures of polymers, functional additives and post-process residues. Surface water contamination with microplastics includes: primary microplastics from resins used in industry and secondary microplastics produced during fragmentation of larger pieces of polymers. Despite the increasing amount of scientific research into plastics in the environment, research into the aging of microplastics remains limited. The consumption of micro- and nanoplastics has been observed in many invertebrate species, especially in filtering organisms, e.g. shellfish and clams. Changes caused by the aging process of microplastics may affect their biological activity and sorption processes. There are scientific reports indicating the possibility of transferring into living organisms, hydrophobic, toxic organic compounds adsorbed on the surface of microparticles of plastics. It is also possible to release harmful functional additives. Many articles have been published on sorption on plastics: polycyclic aromatic hydrocarbons, selected pharmaceuticals and personal care products. However, no studies have been conducted to date on the interaction of microplastics with antidepressants. Antidepressants are one of the most important classes of drugs that are released into surface waters. They affect aquatic organisms already at low concentrations, in the range of several μg / l. Moreover, the use of antidepressants has skyrocketed worldwide due to the global "epidemic of depression". Protozoa play an important role in the aquatic environment as first order consumers. Ciliates - filter feeders feed on bacteria, suspended organic matter and phytoplankton. They are an important link in the food chain from bacteria to higher organisms. Therefore, they can be important vectors carrying adsorbed and absorbed toxic substances, including microplastics, in food network.
The first aim of the project is to assess the acute and chronic toxicity of different types of microplastics (polystyrene, PET and polyvinyl chloride; both colorless and colored) for ciliates: Spirostomum ambiguum and Tetrahymena thermophila. Both raw and aged plastics will be assessed. The microplastics will be aged in the Atlas SUNTEST CPS + accelerated aging apparatus, as well as by incubation for 6 and 12 months in a climatic chamber. We believe that inert particles will be eaten by protozoa and can affect their vital functions: eating behavior and growth rate. We expect that aging and weathering of plastics will have an impact on toxicity by changing the composition, shape and physicochemical properties of particles. In the food intake / excretion test, the protozoa will be immobilized and observed under the KEYENCE VHZ 700 microscope. The second aim of the project is to evaluate the effect of microplastics on the toxicity and bioaccumulation of antidepressants (fluoxetine, sertraline, paroxetine and duloxetine) in protozoa. Our previous research indicates that S. ambiguum is highly sensitive to sertraline and other antidepressants. We believe that microplastics can serve as vectors for the transport of toxic substances into cells, and the process depends on the type of plastic and environmental conditions, especially pH and salinity. Parallel to the bioaccumulation assessment, the sorption and desorption of antidepressants on microplastics (at different pH values) will be analyzed. We believe that drugs adsorbed from the aquatic environment can be desorbed in the acidic environment of food protozoa. Trace analysis of antidepressants in water and protozoan cells will be performed by mass spectrometric detection chromatography. An important novelty of the project is the use of two protozoa: a very large S. ambiguum and a small T. thermophila differing in the metabolic rate and growth rate. In addition, the research will use microplastic particles with natural, irregular shapes, obtained from products available on the market, both raw and aged. Finally, interactions between chemically inert particles and antidepressants will be assessed. These studies will expand our understanding of the fate of these pollutant classes in the aquatic environment.