# Accumulation of Spherical Microplastics in Earthworms Tissues-Mapping Using Raman Microscopy
## 1 Introduction  
Economic development and the constant demand for new materials have made plastics production one of the main branches of the manufacturing industry [1] Modifications and enrichment with stabilizers and dyes create many new types of plastics every day, more resistant to mechanical and biotic factors. According to various sources, a small part of used or damaged polymers is recycled (6-14%), and the rest goes to landfills or directly to ecosystems in the form of illegal dumps [2]. Despite their strength and resistance, plastics--as they are commonly called--gradually degrade, creating smaller and smaller particles [3]. According to the current nomenclature, these particles are called microplastics. There are many different types of microplastics, according to their chemical composition, origin, size, shape, and even color, but they all have a common denominator, which is the threat to the environment when left uncontrolled [4]. Numerous studies have documented the negative, often toxic, effects of microplastics on organisms. In the case of plants, germination, i.e., metabolic processes related to germination [5], adventitious root development, a decrease in biomass or the efficiency of the photosynthetic process [6], at the biochemical level, exposure to microplastics may be associated with increased levels of oxidative stress markers such as glutathione transferase (GST) and catalase (CAT), disruption of water-electrolyte and endocrine balance, which is associated with generative plant development [7]. There are reports of positive effects of plastic particles on plants, such as the longitudinal growth of roots or the stimulation of carotenoid synthesis [8], but these should be considered undesirable effects due to the presence of contamination. In the case of animals, the scale of research conducted appears extremely extensive, covering marine and terrestrial organisms of mammals, birds, fish,and invertebrates, with the smallest number of publications on reptiles. Relevant data are contained in an article by [PERSON] et al. (2019), in which the authors emphasize the significant differences between studies of organisms in laboratory conditions and animals in the wild, with the implication that studies conducted using a single material under control conditions do not reflect both the variability of contaminants in the environment and the complexity of processes and mechanisms in an aquatic ecosystem, for example. Thus, some results may be overestimated relative to their actual values. Plastic particles can induce several changes once they enter the body, especially when they carry contaminants and toxins on their surface. In most species, the presence of microplastics can cause similar effects, such as decreased individual weight, gastrointestinal damage, accumulation in the liver or intestines, and effects on enzymatic activity and oxidative stress. In addition, many detailed and specific studies have been published on muscle dysplasia in birds, gill inflammation in fishes, impaired homeostasis in cephalopods, or basophilic cell volume in molluss ([PERSON] et al., 2019). The greatest scientific challenge related to plastics is the possibility of their safe biodegradation, quick detection in various environments, and unification of analytical methodology. From the point of view of industrial development and the need for cheap materials, these challenges turn out to be extremely difficult to implement. Currently, equipment is used that, based on the introduced database, can determine the plastic content in the sample with high accuracy, such as Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Attenuated Total Reflection FTIR (ATR FTIR), Pyrolysis-gas Chromatography-Mass Spectrometry (Pyro-GC MS), Thermoextraction and Desorption Coupled With Gas Chromatography-Mass Spectroscopy (TED-GC-MS).