The distribution and abundance of microplastics into the world are so extensive that many scientists use them as key indicators of the recent and contemporary period defining a new historical epoch: The Plasticene. However, the implications of microplastics are not yet thoroughly understood. There is considerable complexity involved to understand their impact due to different physical–chemical properties that make microplastics multifaceted stressors. If, on the one hand, microplastics carry toxic chemicals in the ecosystems, thus serving as vectors of transport, they are themselves, on the other hand, a cocktail of hazardous chemicals that are added voluntarily during their production as additives to increase polymer properties and prolong their life. To date, there is a considerable lack of knowledge on the major additives of concern that are used in the plastic industry, on their fate once microplastics dispose into the environment, and on their consequent effects on human health when associated with micro and nanoplastics. The present study emphasizes the most toxic and dangerous chemical substances that are contained in all plastic products to describe the effects and implications of these hazardous chemicals on human health, providing a detailed overview of studies that have investigated their abundance on microplastics. In the present work, we conducted a capillary review of the literature on micro and nanoplastic exposure pathways and their potential risk to human health to summarize current knowledge with the intention of better focus future research in this area and fill knowledge gaps.

Chromium is a potentially toxic metal occurring in water and groundwater as a result of natural and anthropogenic sources. Microbial interaction with mafic and ultramafic rocks together with geogenic processes release Cr (VI) in natural environment by chromite oxidation. Moreover, Cr (VI) pollution is largely related to several Cr (VI) industrial applications in the field of energy production, manufacturing of metals and chemicals, and subsequent waste and wastewater management. Chromium discharge in European Union (EU) waters is subjected to nationwide recommendations, which vary depending on the type of industry and receiving water body. Once in water, chromium mainly occurs in two oxidation states Cr (III) and Cr (VI) and related ion forms depending on pH values, redox potential, and presence of natural reducing agents. Public concerns with chromium are primarily related to hexavalent compounds owing to their toxic effects on humans, animals, plants, and microorganisms. Risks for human health range from skin irritation to DNA damages and cancer development, depending on dose, exposure level, and duration. Remediation strategies commonly used for Cr (VI) removal include physico-chemical and biological methods. This work critically presents their advantages and disadvantages, suggesting a site-specific and accurate evaluation for choosing the best available recovering technology.

Fourier transform infrared (FTIR) is a spectroscopy technique widely used to identify organic materials. It has recently gained popularity in microplastic (MP) pollution research to determine the chemical composition of unknown plastic fragments. However, it could also be used to evaluate the degree of ageing of MPs collected from the environment. In this context, the principal aim of our research has been to qualitatively evaluate the natural weathering of environmental MPs collected in an Italian freshwater body (the Ofanto River) using ATR-FTIR technology. Furthermore, we compared environmental particles to weathered artificial MPs under controlled light and temperature conditions and to unaltered pristine materials to assess the results. FTIR spectra were acquired using a Nicolet Summit FTIR (ThermoFisher Scientific) equipped with an Everest ATR with a diamond Crystal plate and a DTGS KBr detector (wavenumber range 4000–500 cm⁻¹, 32 scans per spectrum, spectral resolution of 4 cm⁻¹). The degree of ageing was assessed using three different indexes known to be related to changes in MPs: Carbonyl Index (CI), Hydroxyl Index (HI), and Carbon-Oxygen Index (COI). The overall results showed that the regions reflecting changes (hydroxyl groups, peaks from 3100 to 3700 cm⁻¹, alkenes or carbon double bonds, 1600 and 1680 cm⁻¹, and carbonyl groups, 1690 and 1810 cm⁻¹) appeared significantly modified in artificial and natural weathered particles compared to the pristine materials. The indexes calculated for polymers degraded under the artificial photo and thermo ageing conditions displayed a general tendency to increase with the time in contact with irradiation time. Particular enhancements of CI of PS fragment and PE pellet, HI of PE and PS fragments and PE pellet, and COI of PS fragment were observed. Otherwise, the following incubation of the same particles at a constant temperature of 45 °C did not further affect the chemical composition of the particles. Moreover, new unique peaks were also observed in the freshwater particles, almost all in the fingerprint region (1500–500 cm⁻¹). Differences in CI, HI, and COI were evidenced among the different morphological MP shapes. On the one hand, the CI calculated for the environmental PE pellets showed values ranging from 0.05 to 0.26 with a mean value of 0.17 ± 0.10. Most samples (57%) presented a CI with values between 0.16 and 0.30. On the other hand, fragments presented slicer modifications in the carbonyl region with CI values lower than pellets (0.05 ± 0.05). This index helps evaluate the degradation of PE MPs by UV light, increasing with enhancing residence time in the environment. Conversely, fragments showed greater values of HI (5.90 ± 2.57) and COI (1.04 ± 0.48) than pellets, as well as lines, which presented the maximum value of HI (11.51). HI is attributed to the bond vibrations of hydroxyl, carboxyl, or phenol groups. In contrast, COI is frequently attributed to the vibrations of C_O bonds found in carbohydrates, alkanes, secondary alcohols, and ketones. In conclusion, our results showed characteristics spectra acquired from environmental particles compared to pristine and artificial aged ones. The interpretation of our main results emphasizes the need to conduct ecotoxicological experimental studies using naturally weathered particles due to the unicity of their properties, which are more helpful for understanding microplastic pollution effects.

Research on microplastics (MPs) in the terrestrial environment is currently at a still embryonal stage. The current knowledge concerning poorly known diffuse sources of MPs pollution in terrestrial ecosystems have been considered in this work. In addition, a particular focus on the presence, mechanism of absorption and effects of MPs in plants has also been provided. Research concerning microplastics in urban areas and their intake by Tyre and Road Wear Particulates (TWRP) demonstrated a high contribution of this plastic debris to microplastic pollution, although quantification of these inputs is challenging to assess because studies are still very few. Around 50% of particles are expected to remain in the roadside soil, while the rest is transported away by the runoff with high concentrations of TRWP with a size ranging between 0.02 and 0.1 mm. Natural and anthropic environments like temporary ponds, stormwater retention ponds and small waterbodies were considered sensitive connecting ecosystems rich in biodiversity between terrestrial and aquatic environments. Even if studies are not yet exhaustive and just eight studies were currently published concerning these ecosystems, considerable values of MPs were already observed both in the sediment and water phase of ponds. Although still poorly explored, agricultural environments were already demonstrated to hide a significant number of microplastics linked mainly to agricultural activities and practices (e.g. mulch, sewage and compost fertilisation). However, the microplastics transportation processes into the soil are still understudied, and a few works are available. Microplastics and primarily nanoplastics presence was also observed in common edible plants (fruit and vegetables) with alarming Estimated Daily Intakes ranging from 2.96 × 10⁰⁴ to 4.62 × 10⁰⁵ (p kg^-1 day^-1) for adults depending on species. In addition, adverse effects on plants growth, photosynthetic activity, antioxidant system and nutritional values of several common fruits and vegetables were also demonstrated by several studies.

Microplastics have recently been stated as being remarkable contaminants of all environmental matrices. The lack of consistent and standardised methods and protocols used to evaluate and quantify microplastics present in riverine systems made a comparison among different studies a critical issue. Based on literature research and the practical expertise of the authors, this work presents a complete collection and analysis of procedures concerning the monitoring of microplastics in riverine environments, focusing on their sampling and analytical protocols to identify, quantify, and characterise them. Further details regarding the advantages and disadvantages of each analytical technique described, such as general recommendations and suggestions, are provided to give practical support for analytical procedures. In particular, microplastics studies consist firstly of their sampling from the aquatic compartment (aqueous and solid phase). Based on the goal of the research, specific devices can be used to collect particles from different matrices. It follows their quantification after extraction from the environmental matrix, adopting different protocols to isolate microplastics from a large amount of organic matter present in a riverine system. In the end, additional qualitative analyses (e.g., RAMAN and FTIR spectroscopy, GC-MS) are required to identify the chemical composition of particles for a better image regarding the abundance of polymer types, their origin, or other information related to manufacturing processes.