Microplastic ingestion in aquatic and soil biota: A comprehensive review of laboratory studies on edible size and intake pattern.

Microplastic contamination is ubiquitous and can be transferred through the food chain to humans. However, studies on microplastic size have mainly focused on large animals with a body length >20 mm. To address this gap, we conducted a comprehensive review of 169 laboratory studies to determine the edible size of microplastics for macrofauna and flora in aquatic and soil biota. Our findings indicate that microplastics with a size of <300 µm and 1 µm, respectively, are edible for these organisms, which are positioned at the base of the food chain. We also analyzed intake and depuration patterns and identified factors affecting microplastic ingestion. Our study fills an important knowledge gap by identifying the range of microplastic sizes that can enter the food chain and be transferred to humans. The study findings have strong implications for the ecological risk assessment of microplastics and suggest a starting point for mitigating this threat.

Translocation and chronic effects of microplastics on pea plants (Pisum sativum) in copper-contaminated soil.

Microplastics (MPs) released into soil environments, along with the existing pollutants in soil, may have adverse effects on plants. However, the chronic effects of MPs in soils contaminated with heavy metals on crop plants remain unidentified. This study aimed to investigate the chronic effects of MPs (polystyrene, 20 nm) on the reproductive and nutritional status of pea crop plant (Pisum sativum) grown in Cu- (40 mg/kg) and MP-contaminated soils (40, 20 mg/kg). The crop yield reduced in all groups, with an evident decrease in the complex exposure group (comprising MPs and Cu). Moreover, significant changes in plants were identified regarding the weight, color, amino acids, and protein content of peas. Nutrient content in beans increased by MP exposure in single and complex exposure groups. Cu accumulation did not differ in the presence and absence of MPs. Additionally, MPs that infiltrated into incomplete casparian strips during root formation translocated into aerial parts via the apoplast pathway along the cell walls of the vascular bundle. Therefore, long-term exposure to MPs in soil can significantly affect plants while collective application of Cu and MPs imposed severe damage. The changes in the crop quality and nutrient contents may in turn affect human health through the food chain.

Validation of the paper-disc soil method using soil alga Chlorococcum infusionum to quantitatively determine the toxicity of heavy metals.

The paper-disc soil method is a soil algal bioassay used to assess soil water transfer in polluted soils. Although this ecotoxicological method was first established in 2016 to assess soil pollution, quantitative toxicity assessments of Cu- or Ni-treated soil and in situ or ex situ soils polluted with other heavy metals (HMs) have not been widely conducted. In this study, the paper-disc soil method was validated under different test conditions. The validated paper-disc soil method was used to quantitatively investigate the toxicity of four HMs (As, Cd, Cr, and Zn). Based on the results, the test species, initial inoculation concentration in the algal-dispersed solution, water content, light intensity, and exposure duration were proposed as Chlorococcum infusionum, 3 × 106 cells/mL in Bold's basal medium, 80% water-holding capacity, 4000 ± 500 lx, and 6 days, respectively. The toxicity of HMs was quantified using the validated paper-disc soil method, and the half-maximal effective concentration values for biomass were calculated as 22.49 (21.26-23.78) mg Cr/kg dry weight (dw) soil, 42.72 (38.64-47.24) mg Cd/kg dw soil, 57.79 (55.46-60.21) mg As/kg dw soil, and 183.06 (175.38-191.06) mg Zn/kg dw soil. The paper-disc soil method using the soil alga C. infusionum was validated by quantitatively evaluating the test conditions and toxicity of HMs. Our results provide important quantitative toxicity data for soil algae exposed to HMs and a basis for standardizing the paper-disc soil method using soil algae.

Microplastics from shoe sole fragments cause oxidative stress in a plant (Vigna radiata) and impair soil environment.

Shoe sole fragments are generated by sole abrasion, which is unavoidable. These fragments can enter the soil ecosystem. However, limited studies have evaluated their effects on soils and plants. Here, we aimed to evaluate the toxicity of shoe sole fragments on a crop plant, Vigna radiata (mung bean). Shoe sole fragments (size: 57-229 µm) were obtained from four shoe types (trekking shoes, slippers, sneakers, and running shoes) and plant toxicity assessments were performed. Additionally, the fragments were leached for 30 d, and potentially toxic leachates were identified. Shoe sole fragments exhibited adverse effects depending on the shoe type. The fragments of soles from sneakers increased the bulk density of the soil but reduced its water holding capacity. Moreover, the microplastic fragments and leachates directly affected plant growth and photosynthetic activities. The fragments of slippers and running shoes boosted plant growth but changed the flavonoid content and photosynthetic factors. Trekking shoe sole fragments did not exhibit plant photoinhibition; however, their leachate inhibited photosynthesis. Overall, it was concluded that shoe sole fragments can cause adverse effects in plants and impair soil environment. Our study findings indicate that it is necessary to develop shoe soles that have less harmful environmental effects.

Cardiogenic shock accompanied by dynamic left ventricular outflow tract obstruction and myocardial bridging after transient complete atrioventricular block mimicking ST-elevation myocardial infarction: a case report.

BACKGROUND: Dynamic left ventricular outflow tract obstruction with or without mitral regurgitation is typically observed in hypertrophic cardiomyopathy, but is also occasionally seen without left ventricular hypertrophy. In this report, we present a case of cardiogenic shock that mimics ST-elevation myocardial infarction, due to dynamic left ventricular outflow tract obstruction with transient mitral regurgitation and myocardial bridging after transient complete atrioventricular block. CASE PRESENTATION: A 65-year-old man with hypertension presented himself at the emergency department with syncope after chest pain. His initial electrocardiography showed inferior ST elevation with profound precordial ST depression and transient complete atrioventricular block. Due to sustained hypotension, an intra-aortic balloon pump was applied. His coronary angiography revealed almost normal right coronary artery and left circumflex artery and only a severe myocardial bridge in the mid-segment of his left anterior descending artery. Instead, severe mitral regurgitation was found without regional wall motion abnormality both in the left ventriculography and the portable echocardiography. However the severe mitral regurgitation completely disappeared in follow up echocardiography the day after. The pressure gradient across the left ventricular outflow tract was measured at 8.95 mmHg during the resting state, and was increased to 38.95 mmHg during the Valsalva state. CONCLUSIONS: The patient presented with a case of cardiogenic shock that mimicked ST-elevation myocardial infarction due to dynamic left ventricular outflow tract obstruction combined with myocardial bridging in the mid-left anterior descending artery.