A Noninvasive Quantitative Method for Evaluating Intestinal Exposure to Microplastics Based on the Excretion and Metabolism Patterns of Microplastics and Their Additives.

Microplastics (MPs) pose potential health risks to the intestinal tract and gut microbiota, a topic that has garnered significant attention. However, the absence of quantitative assessment methods for human gut MP exposure impedes related health risk assessments. Here, we performed long-term continuous exposure experiments on mice using MPs that mimic actual human exposure characteristics. The daily excretion of fecal MPs and the concentrations of phthalates (PAEs) and their metabolites (mPAEs) in serum and urine were detected. The cumulative excretion rate of fecal MPs remains stable at about 93%. A significant linear correlation was observed between MP exposure and concentration of mPAEs in urine for both low MP (LMP; 150 µg of MPs/d) (R2 = 0.90) and high MP (HMP; 360 µg of MPs/d) groups (R2 = 0.97). Moreover, a strong correlation was found between daily PAEs exposure and total MP-associated PAEs exposure in both LMP (R2 = 0.77) and HMP (R2 = 0.88) groups. Based on these findings, we established a noninvasive model and evaluated multiple MP exposure parameters in the human gut across 6 continents, 30 countries, and 133 individuals. This study offers novel insights for the quantitative assessment of in vivo MP exposure and provides technical support for assessing the health risks of MPs.

Analysis of Microplastics in Human Feces Reveals a Correlation between Fecal Microplastics and Inflammatory Bowel Disease Status.

Human ingestion of microplastics (MPs) is inevitable due to the ubiquity of MPs in various foods and drinking water. Whether the ingestion of MPs poses a substantial risk to human health is far from understood. Here, by analyzing the characteristics of MPs in the feces of patients with inflammatory bowel disease (IBD) and healthy people, for the first time, we found that the fecal MP concentration in IBD patients (41.8 items/g dm) was significantly higher than that in healthy people (28.0 items/g dm). In total, 15 types of MPs were detected in feces, with poly(ethylene terephthalate) (22.3-34.0%) and polyamide (8.9-12.4%) being dominant, and their primary shapes were sheets and fibers, respectively. We present evidence indicating that a positive correlation exists between the concentration of fecal MPs and the severity of IBD. Combining a questionnaire survey and the characteristics of fecal MPs, we conclude that the plastic packaging of drinking water and food and dust exposure are important sources of human exposure to MPs. Furthermore, the positive correlation between fecal MPs and IBD status suggests that MP exposure may be related to the disease process or that IBD exacerbates the retention of MPs. The relative mechanisms deserve further studies. Our results also highlight that fecal MPs are useful for assessing human MP exposure and potential health risks.

Phthalates released from microplastics inhibit microbial metabolic activity and induce different effects on intestinal luminal and mucosal microbiota.

The intestine is not only the main accumulation organ of microplastics (MPs), but also the intestinal environment is very conductive to the release of additives in MPs. However, the kinetics of release process, influence factors, and the related effects on gut microbiota remain largely unknown. In this study, a mucosal-simulator of the human intestinal microbial ecosystem (M-SHIME) was used to investigate the influence of gut microbiota on the release of phthalates (PAEs) from MPs and the effects of MPs on the intestinal luminal microbiota and mucosal microbiota. We found that di-(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DBP), and dimethyl phthalate (DMP) were the dominant PAEs released in the gut. Gut microbiota accelerated the release of PAEs, with the time to reach the maximum release was shortened from 7 days to 2 days. Moreover, MPs induced differential effects on luminal microbiota and mucosal microbiota. Compared with mucosal microbiota, the luminal microbiota was more susceptible to the leaching of PAEs from MPs, as evidenced by more microbiota alterations. MPs also inhibited the metabolic activity of intestinal flora based on the reduced production of short chain fatty acids (SCFA). These effects were mainly contributed by the release of PAEs. Acidaminococcus and Morganella were simultaneously correlated to the release of PAEs and the inhibition of metabolic activity of intestinal microbiota and can be used as indicators for the intestinal exposure of MPs and additives.

Effects of chronic exposure to different sizes and polymers of microplastics on the characteristics of activated sludge.

Wastewater treatment plants (WWTPs) have become an important source of microplastics (MPs) contamination and most MPs remain in the sludge inducing potential impacts on sludge disposal. However, little is known about the influence of MPs on the characteristics of sludge, which is essential for sludge disposal. In this study, the dewaterability of activated sludge in response to chronic exposure (60 days) to MPs of different sizes (213.7 nm ~ 4.2 mm) and polymers (polystyrene, polyethylene, and polyvinyl chloride) were investigated. Overall, different particle sizes caused more evident effects on sludge dewatering than different polymer types did. Millimeter MPs (~4 mm) dramatically reduced the dewaterability of sludge by 29.6% ~ 47.7%. These effects were mainly caused by the physical crushing of MPs on sludge flocs, except polyvinyl chloride (PVC)-MPs, possibly containing additives, induced toxicity on sludge. Moreover, 100 mg/L nano-size MPs (213 nm) also reduced the dewatering performance of sludge. The potential mechanism is that nano-size MPs inhibited sludge activity and decreased the abundance of key microorganisms, which subsequently altered the composition and spatial distribution of extracellular polymeric substances (EPS), and finally impeded sludge dewatering. Our results highlight the impacts of different sizes of MPs on the characteristics of sludge, affecting the final disposal of sludge.

Enhanced reproductive toxicities induced by phthalates contaminated microplastics in male mice (Mus musculus).

It has been demonstrated that microplastics (MPs) can transport phthalate esters (PAEs) into the tissues of mice. However, the influence of MPs on accumulation of PAEs and the combined toxicity need profound investigation. In this study, the bioaccumulation of PAEs and reproductive toxicity due to contaminated MPs exposure were investigated. After exposure to PAE-contaminated MPs for 30 days, significantly increased accumulation of PAE was observed in the liver and gut but not in the testis, which are ascribed to the distribution of MPs in tissues. Herein, most micro-size MPs accumulated in the gut and liver, while only a few nano-size MPs entered the Sertoli cells. Compared with virgin MPs and PAEs alone, PAE-contaminated MPs induced enhanced reproductive toxicities manifested by greater alterations in sperm physiology and spermatogenesis. The enhanced toxicities were also confirmed by the testicular transcriptomic alterations and aggravated oxidative stress induced by PAE-contaminated MPs. These aggravated reproductive toxicities were not caused solely by PAE, but may also be caused by the sensitization effect of oxidative stress induced by MPs. Our results highlight the potential reproductive toxicity on male terrestrial mammals due to co-exposure of MPs and plastic additives and provide valuable insights into the mechanism of combined toxicity of MPs and other pollutants.

Microplastics enhance the developmental toxicity of synthetic phenolic antioxidants by disturbing the thyroid function and metabolism in developing zebrafish.

Coexposure of MPs and other contaminants adsorbed from the environment has raised many attentions, but the understanding of the combined effects of MPs and plastic additives are limited. Butylated hydroxyanisole (BHA), a widely used synthetic phenolic antioxidant in plastics, has gained high concerns due to their unintended environmental release and potential threat to aquatic organisms. This study was conducted to reveal the influences of MPs on the bioaccumulation and developmental toxicity of BHA in zebrafish larvae. As a result, MPs promoted the accumulation of BHA in zebrafish larvae and enhanced the toxicity of BHA in larvae development manifested by reduced hatching rates, increased malformation rates and decreased calcified vertebrae. Although the concentration of MPs was not sufficient to cause obvious developmental toxicity, the impacts of MPs on thyroid hormones status might contribute to the aggravated join toxicity. The metabolomic mechanism was revealed to be that the coexposure of BHA and MPs affected the development of zebrafish larvae via disturbing the metabolism of arachidonic acid, glycerophospholipid, and lipids. Our results emphasized that MPs, even at the nontoxic concentrations, in combination with additives caused health risk that should not be ignored.

An efficient method for extracting microplastics from feces of different species.

Concerns have been raised regarding the ingestion of microplastics (MPs) by numerous organisms including humans. However, no efficient and standardized methods are available for extracting MPs from feces. In this study, we introduce a novel approach with high digestion efficiency that involves using Fenton's reagent and nitric acid to remove feces solids. Firstly, Fenton's reagent was used to degrade small solids and decompose large solids into small pieces. Secondly, nitric acid was used to digest the remaining solids and filters. Furthermore, absolute ethyl alcohol was used to remove the mineral residues wrapped on the plastic surfaces and disperse MPs. By using this method, 97.78 % MPs can be recovered from human and chicken feces, and no significant changes were observed in the physical and Raman spectral properties of different polymer types of MPs. This method has also been verified by extracting MPs from field feces. Overall, the proposed method can efficiently digest feces solids and extract MPs with higher recovery rate, less intermediate steps and less damage, which can serve as an economical and feasible method for the detection of MPs in the feces of different species.

Microplastics release phthalate esters and cause aggravated adverse effects in the mouse gut.

Increasing evidence shows that microplastics (MPs) have the potential to act as carriers and transport contaminants into organisms, as well as induce serious health risks. Here we endeavored to address for the first time whether MPs could transport and release phthalate esters (PAEs) into mouse gut and the consequential toxic effects. As a result, MPs could adsorb PAEs, transport PAEs into the gut and cause intestinal accumulation. The accumulation of PAE in the gut followed the order of DEHP > DBP > DEP > DMP, which was the same order for the adsorption of PAEs on MPs. After exposed to DEHP-contaminated MPs for 30 days, significantly increased intestinal permeability and enhanced intestinal inflammation were induced compared with individual MPs and DEHP according to biochemical and histological analysis. Transcriptomic analysis found that 703 genes were differentially regulated and these genes are involved in oxidative stress, immune response, lipid metabolism, and hormone metabolism. Moreover, gut microbiota analysis found that the combined exposure of MPs and DEHP also caused alterations in gut microbiota composition, especially some energy metabolism and immune function related bacteria were significantly changed in the relative abundance. The aggravated effects on intestinal inflammation and metabolic disorders caused by DEHP-contaminated MPs may attribute to increased DEHP accumulation, changed exposure pathway, and shared toxic mechanisms. Our results provide valuable information for the health risk of MPs and plastic additives.