Microplastics and nanoplastics (MNPs) represent a pervasive environmental pollutant, raising significant concerns about potential health effects on humans. These tiny plastic particles have been detected across various environmental matrices, including air, water, soil, and food sources. While the adverse impacts of MNPs on wildlife and ecosystems are well-documented, understanding their effects on human health is still in its infancy. This study aims to comprehensively review existing case reports documenting adverse health outcomes associated with MNPs exposure. Through an extensive literature search, relevant articles were identified and analyzed. MNPs exposure primarily occurs through ingestion and inhalation routes. Health effects on the digestive system include oxidative stress, inflammation, dysbiosis, and metabolic disorders, with cases linking MNPs exposure to gastrointestinal injury and liver dysfunction. Respiratory system impacts include asthma exacerbation and hypersensitivity pneumonitis, particularly in industries involving plastic production. MNPs exposure has also been associated with nervous system conditions, reproductive toxicity, skeletal system interference, excretory system disruption, and cardiovascular morbidity and mortality. Despite limited case reports, the widespread presence of MNPs warrants further investigation into their potential health risks. This study underscores the urgency of understanding and mitigating the adverse health effects posed by MNPs exposure. Further research is imperative in order to comprehensively assess and address the dangers associated with MNPs contamination in the environment.

To highlight the key role of global warming on the toxicity of contaminants, the cardiovascular toxicity of nanoparticles (NPs) was estimated in developing zebrafish (Danio rerio) at different exposure temperatures, and the toxicity mechanisms were explored via multi-omic analyses. Polystyrene NPs (50 nm) at 0.1 mg·L-1 entered zebrafish embryos at 24 h post-fertilization and caused cardiovascular toxicity in the developing zebrafish at 27 ℃. This was explained by the down-regulation of the branched-chain amino acid and insulin signaling pathways owing to induced oxidative stress. Elevated exposure temperatures promoted the accumulation of NPs in developing zebrafish, increased the levels of oxidative stress and enhanced the oxidative phosphorylation rate in mitochondria, thus resulting in an additive effect on the mortality of zebrafish larvae. Notably, elevated exposure temperatures reduced the cardiovascular toxicity of NPs, as the effective concentration of NPs for inhibiting embryonic heartbeat rate increased from 0.1 mg·L-1 at 27 ℃ to 1.0 mg·L-1 at 30 ℃. Experiments of transgenic zebrafish Tg(myl7:GFP) and multi-omic analyses revealed that elevated temperatures enhanced the myocardial contractility of larvae, thus reducing the cardiovascular toxicity of NPs. However, the health risks of enhanced myocardial contraction caused by NP exposure at elevated temperatures requires further consideration.

Mismanaged plastic litter submitted to environmental conditions may breakdown into smaller fragments, eventually reaching nano-scale particles (nanoplastics, NPLs). In this study, pristine beads of four different types of polymers, three oil-based (polypropylene, PP; polystyrene, PS; and low-density polyethylene, LDPE) and one bio-based (polylactic acid, PLA) were mechanically broken down to obtain more environmentally realistic NPLs and its toxicity to two freshwater secondary consumers was assessed. Thus, effects on the cnidarian Hydra viridissima (mortality, morphology, regeneration ability, and feeding behavior) and the fish Danio rerio (mortality, morphological alterations, and swimming behavior) were tested at NPLs concentrations in the 0.001 to 100 mg/L range. Mortality and several morphological alterations were observed on hydras exposed to 10 and 100 mg/L PP and 100 mg/L LDPE, whilst regeneration capacity was overall accelerated. The locomotory activity of D. rerio larvae was affected by NPLs (decreased swimming time, distance or turning frequency) at environmentally realistic concentrations (as low as 0.001 mg/L). Overall, petroleum- and bio-based NPLs elicited pernicious effects on tested model organisms, especially PP, LDPE and PLA. Data allowed the estimation of NPLs effective concentrations and showed that biopolymers may also induce relevant toxic effects.

Polystyrene nanoparticles are the most investigated type of nanoplastics in environmental hazard studies. It remains unclear whether nanoplastic particles pose a hazard towards aquatic organisms. Thus, it was our aim to investigate whether the existing studies and data provided therein are reliable in terms of data completeness. We used the example of Daphnia spp. studies for the purpose of polystyrene nanoplastic (nanoPS) hazard evaluation. First, a set of quality criteria recently proposed for nanoplastic ecotoxicity studies was applied. These rather general criteria for all types of nanoplastics and different test organisms were then, in the second step, tailored and refined specifically for Daphnia spp. and nanoPS. Finally, a scoring system was established by setting mandatory (high importance) as well as desirable (medium importance) criteria and defining a threshold to pass the evaluation. Among the existing studies on nanoPS ecotoxicity for Daphnia spp. (n = 38), only 18% passed the evaluation for usability in hazard evaluation. The few studies that passed the evaluation did not allow for conclusions on the hazard potential of nanoPS because there was no consensus among the studies. The greatest challenge we identified is in data reporting, as only a few studies presented complete data for hazard evaluation.

Plastic pollution is a serious problem in aquatic systems throughout the world. Despite the increasing number of studies addressing the impact of macro- and microplastics on biota, there is still a significant knowledge gap regarding the effects of nanoplastics alone and in combination with other contaminants. Among the aquatic contaminants that may interact with nanoplastics is arsenic (As), a metalloid found in estuarine and coastal ecosystems, pernicious to benthic organisms. This study aimed to understand how a parental pre-exposure to 100 nm polystyrene nanoplastics (PS NPs) would influence the response of Hediste diversicolor to exposure to arsenic in terms of behaviour, neurotransmission, antioxidant defences and oxidative damage, and energy metabolism. The obtained data revealed an increase in burrowing time and a significant inhibition in cholinesterase activity in all polychaetes exposed to As, regardless of the pre-exposure to PS NPs. Oxidative status was altered particularly in parentally exposed organisms, with damage detected in terms of lipid peroxidation at 50 μg/L and protein carbonylation at 50 and 250 μg As/L exposed organisms when compared to control. Overall, data shows that parental pre-exposure to plastics influences the response of aquatic organisms, increasing their susceptibility to other contaminants. Thus, more studies should be performed with other environmental contaminants, to better understand the potential increased risk associated with the presence of nanoplastics to aquatic ecosystems.

Plastic production has been rising consistently in the last 30 years and with it, the presence of plastic particles in the environment. A decrease in size often increases the bioavailability and reactivity of the particles. In this study the impact of polystyrene (PS; 22 nm) and polymethylmethacrylate (PMMA; 32 nm) nanoparticles on zebrafish embryo-larval stages was assessed by studying mortality, hatching, morphological features, and biochemical endpoints (associated with neurotransmission, antioxidant status and oxidative damage, and energy metabolism) after 96 h exposure, and swimming behavior after 120 h exposure. Organisms exposed to PMMA nanoparticles exhibited higher mortality and pericardial edema than those exposed to PS nanoparticles but displayed less effects on swimming behavior. Biochemical endpoints were altered to a higher degree in organisms exposed to PS nanoparticles (acetylcholinesterase, glutathione S-transferase and catalase activities) but higher peroxidative damage was found after exposure to lower concentrations of PMMA nanoparticles. Both types of nanoparticles affected energy metabolism with higher levels of glycogen found in animals exposed to PS nanoparticles. The use of integrated biomarker response index confirmed that PS nanoparticles had a higher impact on biochemical endpoints of zebrafish.

The concern about microplastic (a group of polymers) in the environment may cause us to overlook a more substantial problem: microplastics will fragment into nanoplastics. This fragmentation will lead to a high number of nanoplastics particles. Such nanoplastic can be taken up by cells, as opposed to microscale particles that are either not or to much less extend taken up. Fragmentation into nano will also release materials previously safely embedded in the polymer. We here present results from 25 OECD/ISO in vivo hazard tests, and beyond, e.g. extended exposure duration, with Enchytraeus crypticus, using pristine nano-scale materials (NMs) [CuO, Fe2O3, Organic Pigment, MWCNT], fragmented products (polymers) with these NMs embedded in the matrices (FP_NM), and fragmented polymers without NMs (FP) [covering the 4 major plastic types: Acrylic, Polyethylene, Polypropylene and Epoxy]. For example, MWCNTs induced a highly significant population decrease after extended period of 60 days, despite having no impact after 28 days\' exposure, the standard OECD duration. We conclude, that the standard tests were not suitable to evaluate hazards of these plastic fragments, weathering/ageing of materials is recommended, and extension of test duration can add value to the testing of NMs. We must refocus the concern to testing with polymers (not only \"plastics\"), from micro-to nano-polymers, and from aquatic to terrestrial environments.