Uptake, transport and accumulation of micro- and nano-plastics in terrestrial plants and health risk associated with their transfer to food chain - A mini review

Mechanism of S-Palmitoylation in Polystyrene Nanoplastics-Induced Macrophage Cuproptosis Contributing to Emphysema through Alveolar Epithelial Cell Pyroptosis

More than microplastics, nanoplastics may pose a greater toxic effect on humans due to their unique physicochemical properties. Currently, research on lung diseases caused by respiratory exposure to nanoplastics is scarce, with epigenetic mechanisms warranting further investigation. In the present study, we exposed rats to polystyrene nanoplastics (PS-NPs) via an oral-nasal exposure system and found that PS-NPs exposure resulted in emphysema. Mechanistically, PS-NPs entered macrophages and competitively bound to sigma nonopioid intracellular receptor 1 (SIGMAR1), leading to an increase in free zDHHC palmitoyltransferase 14 (zDHHC14). This, in turn, caused elevated palmitoylation of solute carrier family 31 member 1 (SLC31A1) in macrophages, inhibiting its ubiquitination and degradation, thereby enhancing SLC31A1 expression. The increased expression of SLC31A1 promoted cuproptosis of macrophages and elevated tumor necrosis factor-α (TNF-α) secretion, which activated the NLR family pyrin domain containing 3/matrix metallopeptidase 9 (NLRP3/MMP-9) pathway in alveolar epithelial cells (AECs). This process mediated pyroptosis and degradation of extracellular matrix (ECM), resulting in the destruction of alveolar structure and development of emphysema. The findings demonstrate a previously unknown molecular mechanism by which PS-NPs induce emphysema. The findings have implications for the prevention and treatment of respiratory system damage caused by nanoparticles.

Evidence of microplastic accumulation on the surface of lettuce and analysis of contamination sources

Microplastic (MP) pollution has emerged as a significant environmental concern. Microplastics land on vegetable surfaces with airborne deposition and agronomic activities. However, research on the sources of microplastics on vegetable surfaces is limited by the lack of monitoring of microplastics in the growing environment. Therefore, we detected microplastics on lettuce surfaces, in air, and in pesticides to determine the correlation between them. In addition, this study compared microplastics on the surface of different types of lettuce to explore their differences. The results showed that the content, in descending order, was old leaves of leaf lettuce > new leaves of leaf lettuce > nodular lettuce. A total of 19 polymers, mainly polyamide polyethylene and polypropylene, were detected on the surface of the lettuce. The contribution of microplastics on the surface of lettuce was air and pesticides in descending order of origin. Microplastic risk assessment index was determined that the risk level of microplastics on lettuce surfaces could be classed as level IV, indicating a high dietary health risk. The results presented here will enable scientific assessments of the exposure pathways of MPs in fresh vegetables and their potential harm to human health.

First evidence of microplastics in human ovarian follicular fluid: An emerging threat to female fertility

Several studies have assessed the presence of microplastics (MPs) in human biological fluids and tissues highlighting potential health risks associated to oxidative stress, inflammation, immune dysfunction, neurotoxicity and reprotoxicity. However, only few studies have evaluated MP presence and effects in ovarian tissues of mammalians and, to date, no studies have detected MPs in human ovarian follicular fluids. Based on these premises, in this study, 18 women (undergoing assisted reproductive treatment at In Vitro Fertilisation center in Salerno, Southern Italy) were selected to assess the presence of MPs in follicular fluid. Plastic particles < 10 µm were measured using Scanning Electron Microscopy (SEM) coupled with an EDX (X Energy Dispersion) detector. MPs (size <10 µm) were detected in 14 out of 18 samples of follicular fluid, with an average concentration of 2191 particles/mL (0-7181particles/mL) and with a mean diameter of 4.48 µm (3.18-5.54 µm). Moreover, a significant correlation between MP concentration in follicular fluid samples and Follicle-Stimulating Hormone (FSH) (p-value <0.05), as well as a weak (non-significant) correlation with Body Mass Index (BMI), age and 17β-estradiol (E2), was found. On the contrary, no correlation with anti-Müllerian Hormone (AMH), fertilization outcomes, miscarriages, or live birth was observed. Since several studies on animal models have demonstrated the negative effects of MPs on ovarian function, the present study, that verified for the first time the presence of MPs in human follicular fluid, is of great significance for the scientific community in terms of raising awareness of the impact that these increasingly pervasive emerging contaminants have on reproductive function and human health.

Cu-tolerant Klebsiella variicola SRB-4 increased the nanoparticle (NP) stress resilience in garden peas (Pisum sativum L.) raised in soil polluted with varying doses of copper oxide (CuO)-NP

Utilizing metal/nanoparticle (NP)- tolerant plant growth-promoting rhizobacteria (PGPR) is a sustainable and eco-friendly approach for remediation of NP-induced phytotoxicity. Here, Pisum sativum (L.) plants co-cultivated with different CuO-NP concentrations exhibited reduced growth, leaf pigments, yield attributes, and increased oxidative stress levels. Cu-tolerant (800 µM) Klebsiella variicola strain SRB-4 (Accession no. OR715781.1) recovered from metal-contaminated soils produced various PGP traits, including IAA, EPS, siderophore, HCN, ammonia, and solubilized insoluble P. The PGP substances were marginally increased with increasing CuO-NP concentrations. When applied, Cu-tolerant SRB-4 strain increased root length (18%), root biomass (15.3%), total chlorophyll (29%), carotenoids (30%), root N (21%), root P (23%), total soluble protein (20%) nodule number (32%), nodule biomass (39%) and leghaemoglobin content (18%) in 50 µM CuO-NP-exposed peas. Furthermore, proline, malondialdehyde (MDA), superoxide radical, hydrogen peroxide (H2O2) content, and membrane injury in K. variicola-inoculated and 50 µM CuO-NP-treated plants were maximally and significantly (p ≤ 0.05) reduced by 70.6, 26.8, 60.8, and 71.6%, respectively, over uninoculated but treated with similar NP doses. Moreover, K. variicola inoculation caused a significant (p ≤ 0.05) decline in Cu uptake in roots (71%), shoots (65.5%), and grains (76.4%) of peas grown in soil contaminated with 50 µM CuO-NP. The multivariate i.e. heat map and pearson correlation analyses between the NP-treated and PGPR inoculated parameters revealed a significant and strong positive corelation. The NP-tolerant indigenous beneficial K. variicola could be applied as an alternative to enhance the production of P. sativum cultivated in nano-polluted soil systems. Additionally, more investigation is required to ascertain the seed/soil inoculation effect of K. variicola SRB-4 on soil biological activities and different crops under various experimental setups.

Medical exposure to micro(nano)plastics: An exposure pathway with potentially significant harm to human health that should not be overlooked

Micro(nano)plastics (MNPs) are an emerging type of contaminants that are widely present in the environments that people live in. MNPs can enter the human body in a variety of pathways, but the three main ones are through dietary intake, air inhalation, and skin contact. However, it has been discovered that medical plastics used in medical activities also pose potential risks to MNPs exposure as exposure pathways are continuously refined and clarified. Unfortunately, there is currently insufficient study on the exposure of medical plastics and MNPs, and exposure risks and potential health problems are frequently overlooked. This study aimed to close this research gap by searching the databases of China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science for relevant literature. It then filtered out publications that contained information relevant to keywords such as micro(nano)plastics, medical plastics, exposure pathways, and human health in order to do analysis and summary. We discovered that medical plastics are a high-risk source of direct MNPs exposure to the human body, and this exposure could pose a potential harm to human health. Because of the potential harm to human health, this work presents the medical exposure of MNPs for the first time and calls for more research and attention on this vital area.

Foliar implications of polystyrene nanoplastics on leafy vegetables and its ecological consequences

The rise of airborne micro-nanoplastics (MNPs) pollution poses a significant threat to agroecological systems. Despite this issue, there is a critical gap in our understanding of their specific effects on various leafy vegetable species. To address this, we conducted a controlled experiment applying Polystyrene Nanoplastics (PS-NPs) on four leafy vegetables: Brassica rapa var. chinensis, B. rapa var. parachinensis, Amaranthus viridis, and Allium tuberosum. Our results showed that PS-NPs tend to accumulate within the epidermal layers and cuticles of these vegetables, particularly around stomatal apertures. More PS-NPs were found on the adaxial and abaxial side of leaves, compared to the cross-section. The abundance of PS-NPs accumulations varied significantly among the studied species due to differences in leaf structure. Notably, leaves with trichomes trapped more PS-NPs particles. These accumulation significantly reduced chlorophyll content and photosynthetic rates, altering the growth and nutritional quality of the vegetables. Our findings reveal the ecological effects of PS-NPs on the nutrient content, phenotype, physiology, growth and biomass metrics of common leafy vegetables. This highlights the potential for PS-NPs accumulation in edible plant tissues, raising concerns about food security and human health.

Accumulation of Microplastics and Potentially Toxic Elements in Plant Leaves Along an Urbanization Gradient in Bangladesh

Potentially toxic elements (PTEs) and microplastics (MPs) in the atmosphere raise widespread apprehension due to their association with the ecosystem and public health. The accumulation of airborne MPs and PTEs was analyzed in Polyalthia longifolia leaves, and the Pollution Index (PI) was calculated along an industrial, residential, and rural gradient in Bangladesh. Only polyethylene terephthalate (PET) was found in the highest concentration in industrial areas compared to other areas. In leaves, a significantly higher Cd, Pb, and Zn concentration was found in industrial regions compared to residential and rural areas. For Cd, the PI was observed to be higher than 1 in rural areas, indicating a moderate level of pollution; it was higher than 3 in residential areas, showing considerable pollution; and it was found to be more than 6 in industrial areas. The higher concentration of both MPs and PTEs with increasing urbanization reflects the influence of anthropogenic activities. The findings of the study demonstrate the fascinating potential of P. longifolia tree leaves as a promising bioindicator for air quality biomonitoring.

Reductive soil disinfestation influences microbial aging of low-density polyethylene and polyhydroxyalkanoate microplastics and microbial communities in plastispheres

The extensive use of plastic products has led to the accumulation of microplastics (MPs) in agricultural soils, raising concerns about their fate in various environments. Reductive soil disinfestation (RSD) treatment is increasingly being adopted in various countries to address agricultural soil health issues. However, the treatment can alter the soil microbial environment, potentially affecting the fate of contaminants, including MPs. The effect of RSD on the aging of low-density polyethylene (LDPE) and polyhydroxyalkanoates (PHA) MPs was studied through an incubation experiment. The mechanism involved was further investigated by microbial community analysis. The characterization results shown that RSD treatment inhibited the aging of LDPE but promoted the aging of PHA. The results indicated that RSD reshaped the microbial community and reduced the relative abundance of lipid metabolism in the LDPE plastisphere, thereby hindering LDPE aging. Predicted functional genes in the plastispheres were primarily involved in metabolism (77.15-87.48%) and genetic information processing (8.774-12.62%). The enrichment of bacteria related to poly(3-hydroxybutyrate) depolymerase (phaZ) in the PHA plastisphere explained the higher aging degree of PHA during RSD. Some fungus also involved in the MPs aging, while some fungus pathogens can proliferate in the MPs plastispheres. The 3DEEM analysis indicated that PHA MPs aging increased tyrosine-like substances in soil extracts. These findings provide new insights into the ecological implications of RSD and enhance our understanding of microbial communities within plastispheres.

Unveiling the impacts of microplastic pollution on soil health: A comprehensive review

Soil contamination by microplastics (MPs) has emerged as a significant global concern. Although traditionally associated with crop production, contemporary understanding of soil health has expanded to include a broader range of factors, including animal safety, microbial diversity, ecological functions, and human health protection. This paradigm shifts underscores the imperative need for a comprehensive assessment of the effects of MPs on soil health. Through an investigation of various soil health indicators, this review endeavors to fill existing knowledge gaps, drawing insights from recent studies conducted between 2021 and 2024, to elucidate how MPs may disrupt soil ecosystems and compromise their crucial functions. This review provides a thorough analysis of the processes leading to MP contamination in soil environments and highlights film residues as major contributors to agricultural soils. MPs entering the soil detrimentally affect crop productivity by hindering growth and other physiological processes. Moreover, MPs hinder the survival, growth, and reproductive rates of the soil fauna, posing potential health risks. Additionally, a systematic evaluation of the impact of MPs on soil microbes and nutrient cycling highlights the diverse repercussions of MP contamination. Moreover, within soil-plant systems, MPs interact with other pollutants, resulting in combined pollution. For example, MPs contain oxygen-containing functional groups on their surfaces that form high-affinity hydrogen bonds with other pollutants, leading to prolonged persistence in the soil environment thereby increasing the risk to soil health. In conclusion, we succinctly summarize the current research challenges related to the mediating effects of MPs on soil health and suggest promising directions for future studies. Addressing these challenges and adopting interdisciplinary approaches will advance our understanding of the intricate interplay between MPs and soil ecosystems, thereby providing evidence-based strategies for mitigating their adverse effects.

Plastic pollution in terrestrial ecosystems: Current knowledge on impacts of micro and nano fragments on invertebrates

The increasing accumulation of small plastic particles, in particular microplastics (>1 µm to 5 mm) and nanoplastics (< 1 µm), in the environment is a hot topic in our rapidly changing world. Recently, studies were initiated to better understand the behavior of micro- and nanoplastics (MNP) within complex matrices like soil, as well as their characterization, incorporation and potential toxicity to terrestrial biota. However, there remains significant knowledge gaps in our understanding of the wide-extent impacts of MNP on terrestrial invertebrates. We first summarized facts on global plastic pollution and the generation of MNP. Then, we focused on compiling the existing literature examining the consequences of MNP exposure in terrestrial invertebrates. The diversity of investigated biological endpoints (from molecular to individual levels) were compiled to get a better comprehension of the effects of MNP according to different factors such as the shape, the polymer type, the organism, the concentration and the exposure duration. The sublethal effects of MNP are acknowledged in the literature, yet no general conclusion was drawn as their impacts are highly dependent on their characteristic and experimental design. Finally, the synthesis highlighted some research gaps and remediation strategies, as well as a protocol to standardize ecotoxicological studies.

In planta synthesis of silver nanoparticles and its effect on adventitious shoot growth and withanolide production in Withania somnifera (L.) Dunal

Silver (Ag) is a non-essential heavy metal with substantial environmental toxicity but an excellent promotor for plant organogenesis. It is used as an elicitor for secondary metabolite production and for in planta synthesis of metal nanoparticles (MNPs). In the present study, the Ag accumulation and reduction capability of in vitro shoots of Withania somnifera and the toxicity and elicitation effect of Ag on in vitro shoots were explored. In vitro shoot cultures of W. somnifera were treated with different concentrations of silver nitrate for a specific treatment period. Growth index, withaferin A, elemental and electron microscopy analyses were done on silver-treated in vitro shoots of W. somnifera. 1 mM silver nitrate treatment for 12 days period was found to give increased growth index (1.425 ± 0.05c) and withaferin A (2.568 ± 0.08e mg g-1) content. The concentration of bioaccumulated Ag in 1 mM silver nitrate treated in vitro shoot was found to be 50.8 ppm. The presence of nano-Ag was also found in the leaves of 1 mM silver nitrate-treated in vitro shoots. In summary, this is the first report portraying the bioaccumulation and in planta reduction capability of the in vitro shoot system of W. somnifera, which makes it a potential medicinal plant of commercial value for silver contaminated soils.

The effects of polypropylene microplastics on the removal of nitrogen and phosphorus from water by Acorus calamus, Iris tectorum and functional microorganisms

Polypropylene microplastics (PP-MPs), an emerging pollutant, adversely affect the ability of aquatic plants to restore water bodies, thereby compromising the functionality and integrity of wetland ecosystems. This study examines the effects of microplastic stress on the nitrogen and phosphorus removal capacities of Acorus calamus and Iris tectorum, as well as on functional microorganisms within the aquatic system. The findings indicate that under PP-MP stress, the nitrogen and phosphorus absorption capabilities of both plants were diminished. Additionally, there was a significant reduction in the metabolic enzyme activities related to nitrogen and phosphorus in the plants, alongside a notable decrease in leaf nitrogen content. PP-MPs hinder the nutrient uptake of plants, affecting their growth and indirectly reducing their ability to utilize nitrogen and phosphorus. Specifically, in the 10 mg L-1 treatment group, A. calamus and I. tectorum showed reductions in leaf nitrogen content by 23.1% and 31.0%, respectively, and by 14.8% and 27.7% in the 200 mg L-1 treatment group. Furthermore, I. tectorum had higher leaf nitrogen levels than A. calamus. Using fluorescent tagging, the distribution of PP-MPs was traced in the roots, stems, and leaves of the plants, revealing significant growth impairment in both species. This included a considerable decline in photosynthetic pigment synthesis, enhanced oxidative stress responses, and increased lipid peroxidation in cell membranes. PP-MP exposure also significantly reduced the abundance of functional microorganisms involved in denitrification and phosphorus removal at the genus level in aquatic systems. Ecological function predictions revealed a notable decrease in nitrogen cycling functions such as nitrogen respiration and nitrite denitrification among water microorganisms in both treatment groups, with a higher ecological risk potential in the A. calamus treatment group. This study provides new insights into the potential stress mechanisms of PP-MPs on aquatic plants involved in water body remediation and their impacts on wetland ecosystems.

Polystyrene nanoplastics exposure causes erectile dysfunction in rats

Polystyrene nanoplastics (PS-NPs), emerging and increasingly pervasive environmental contaminants, have the potential to cause persistent harm to organisms. Although previous reports have documented local accumulation and adverse effects in a variety of major organs after PS-NPs exposure, the impact of PS-NPs exposure on erectile function remains unexplored. Herein, we established a rat model of oral exposure to 100 nm PS-NPs for 28 days. To determine the best dose range of PS-NPs, we designed both low-dose and high-dose PS-NPs groups, which correspond to the minimum and maximum human intake doses, respectively. The findings indicated that PS-NPs could accumulate within the corpus cavernosum and high dose but not low dose of PS-NPs triggered erectile dysfunction. Moreover, the toxicological effects of PS-NPs on erectile function include fibrosis in the corpus cavernous, endothelial dysfunction, reduction in testosterone levels, elevated oxidative stress and apoptosis. Overall, this study revealed that PS-NPs exposure can cause erectile dysfunction via multiple ways, which provided new insights into the toxicity of PS-NPs.

Microplastics in soils: Production, behavior process, impact on soil organisms, and related toxicity mechanisms

In recent years, microplastics (MPs) pollution has become a hot ecological issue of global concern and MP pollution in soil is becoming increasingly serious. Studies have shown that MPs have adverse effects on soil biology and ecological functions. Although MPs are evident in soils, identifying their source, abundance, and types is difficult because of the complexity and variability of soil components. In addition, the effects of MPs on soil physicochemical properties (PCP), including direct effects such as direct interaction with soil particles and indirect effects such as the impact on soil organisms, have not been reported in a differentiated manner. Furthermore, at present, the soil ecological effects of MPs are mostly based on biological toxicity reports of their exudate or size effects, whereas the impact of their surface-specific properties (such as environmentally persistent free radicals, surface functional groups, charge, and curvature) on soil ecological functions is not fully understood. Considering this, this paper reviews the latest research findings on the production and behavioral processes of MPs in soil, the effects on soil PCP, the impacts on different soil organisms, and the related toxic mechanisms. The above discussion will enhance further understanding of the behavioral characteristics and risks of MPs in soil ecosystems and provide some theoretical basis for further clarification of the molecular mechanisms of the effects of MPs on soil organisms.

Uptake and transport of micro/nanoplastics in terrestrial plants: Detection, mechanisms, and influencing factors

The pervasive dispersion of micro/nanoplastics in various environmental matrices has raised concerns regarding their potential intrusion into terrestrial ecosystems and, notably, plants. In this comprehensive review, we focus on the interaction between these minute plastic particles and plants. We delve into the current methodologies available for detecting micro/nanoplastics in plant tissues, assess the accumulation and distribution of these particles within roots, stems, and leaves, and elucidate the specific uptake and transport mechanisms, including endocytosis, apoplastic transport, crack-entry mode, and stomatal entry. Moreover, uptake and transport of micro/nanoplastics are complex processes influenced by multiple factors, including particle size, surface charge, mechanical properties, and physiological characteristics of plants, as well as external environmental conditions. In conclusion, this review paper provided valuable insights into the current understanding of these mechanisms, highlighting the complexity of the processes and the multitude of factors that can influence them. Further research in this area is warranted to fully comprehend the fate of micro/nanoplastics in plants and their implications for environmental sustainability.