Underlying Degradation of Phthalates via Microbials in Dust from Different Microenvironments

Metabolite Monomethyl Phthalate (MMP) Induces Oxidative Damage in Rat Erythrocytes: Role of Vitamins C and E

Dimethyl phthalate (DMP) can enter the human body and be absorbed into the bloodstream to produce monomethyl phthalate (MMP). MMP in the environment can also enter the bloodstream. However, little is known about the toxicity of the phthalate metabolite MMP in most organisms. In this study, the erythrocyte toxicity of MMP and a preventive approach were investigated using Sprague-Dawley (SD) rats as the model animal under MMP concentrations of 5-250 mg/kg (sub-chronic exposure in vivo) and 1.25-100 μg/mL (acute exposure in vitro). The experimental results indicate that the interaction of MMP with erythrocytes caused oxidative damage, which decreased the number of red blood cells and the hemoglobin content and increased the content of methemoglobin and the iron release of hemoglobin in rat blood. However, the above results were not observed when MMP directly interacted with hemoglobin. The antioxidants vitamin C and vitamin E improved the above blood indicators in rats. The results of this study provide certain theoretical guidance for the evaluation of the potential risks of phthalate metabolites.

Occurrence, Characteristics, and Mixed Reproductive Exposure Risk Assessment of Traditional Phthalates and Their Novel Alternatives in Campus Indoor Dust

Phthalates (PAEs) constitute the primary components of indoor dust pollutants and significantly impact human reproductive health. However, research on novel alternatives to PAEs and the risk assessment of mixed exposure has remained relatively sparse. In this study, 193 indoor dust samples were collected in 2022 from various campus locations, including classrooms, canteens, dormitories, offices, and laboratories. Forty-four traditional PAEs and their alternatives were identified, with concentrations ranging from 0.44 to 91.5 μg/g. Di(2-ethylhexyl) phthalate (DEHP) and dioctyl terephthalate (DEHTH) were the predominant compounds, with mean concentrations of 86.3 and 59.2 μg/g, respectively. The ingestion pathway was the principal route of exposure, with dormitories identified as the primary exposure sites. The mixed reproductive toxicity equivalent factor (TEFmix) of PAEs and their alternatives was developed using a quantitative structure-activity relationship (QSAR) model in conjunction with machine learning algorithms. The TEFmix was found to be lower than the sum of individual PAEs, potentially due to the antagonistic effects of PAE monomers on reproductive health. Under high-exposure scenarios, the TEFmix of PAEs in canteen dust was determined to be 0.245, surpassing values observed in other environments. Females exhibited a higher risk, with dormitories presenting a greater exposure risk than those in other indoor locations. This study provided essential data to inform regulatory measures aimed at mitigating the impact of PAEs and their alternatives in indoor dust on human reproductive health.

TNF/TNFR1 Signaling Mediates DEHP-Induced Hepatocyte Pyroptosis via the GSDMD-mtROS Axis

Di(2-ethylhexyl) phthalate (DEHP), which is widely used in agricultural plastics, accumulates in humans and animals through the food chain over time, resulting in liver toxicity. Recent studies have reported that pyroptosis and mitochondrial damage are closely related to a variety of liver diseases, but the specific mechanism is still unclear. To address this issue, in vitro and in vivo hepatotoxicity models were established. The results demonstrated that exposure to DEHP caused a buildup of MEHP in livers, altered liver metabolite composition, and caused pyroptosis-like changes in hepatocytes. After DEHP treatment, REDOX homeostasis was unbalanced, and mitochondrial reactive oxygen species (mtROS) were overproduced. MEHP exposure activates pyroptosis mediated by TNF/TNFR1 signaling and upregulates the perforating protein GSDMD-N to destroy the mitochondrial membrane of hepatocytes. Above all, this study elucidates the potential involvement of TNF/TNFR1 signaling-mediated pyroptosis in mitochondrial damage and confirms that the regulation of pyroptosis is helpful in maintaining normal mitochondrial function.

Colonization of phthalate-degrading endophytic bacterial consortium altered bacterial community and enzyme activity in plants

Phthalates (PAEs) are widely distributed hazardous organic compounds that pose threats to ecosystems and human health. Endophytic bacteria can effectively eliminate PAEs contamination risk. However, limited information is available regarding the impact of endophytic bacterial colonization on bacterial communities within plants. In this study, the endophytic bacterial consortium EN was colonized in lettuce by seed soaking, root irrigation, leaf spraying, and combined spraying-irrigation, resulting in a marked improvement in plant growth. The findings revealed that consortium EN colonization through combined spraying-irrigation exhibited superior degradation capability with 40.54% PAEs removal from soil. Meanwhile, the residual PAEs in lettuce decreased by 94.05% compared with the uninoculated treatment. High-throughput sequencing analysis indicated that colonization of consortium EN altered the bacterial community in lettuce. Specifically, the relative abundance of the dominant genus Pseudomonas was significantly higher than that in the uninoculated control (P < 0.01). Additionally, colonization enhanced the activities of peroxidase and catalase in lettuce, thereby improving plant resistance. This work offers a theoretical foundation for comprehending the mechanism underlying the bioremediation of PAEs contamination by endophytic bacteria in soil-plant system.

Biodegradation of PAEs in contaminated soil by immobilized bacterial agent and the response of indigenous bacterial community

Phthalic acid esters (PAEs) are common hazardous organic contaminants in agricultural soil. Microbial remediation is an effective and eco-friendly method for eliminating PAEs. Nevertheless, the operational mode and potential application of immobilized microorganisms in PAEs-contaminated soil are poorly understood. In this study, we prepared an immobilized bacterial agent (IBA) using a cedar biochar carrier to investigate the removal efficiency of PAEs by IBA in the soil. We found that IBA degraded 88.35% of six optimal-control PAEs, with 99.62% biodegradation of low-molecular-weight PAEs (DMP, DEP, and DBP). The findings demonstrated that the IBA achieved high efficiency and a broad-spectrum in degrading PAEs. High-throughput sequencing revealed that IBA application altered the composition of the soil bacterial community, leading to an increase in the relative abundance of PAEs-degrading bacteria (Rhodococcus). Furthermore, co-occurrence network analysis indicated that IBA promoted microbial interactions within the soil community. This study introduces an efficient method for the sustainable remediation of PAEs-contaminated soil.

Widespread phthalate esters and monoesters in the aquatic environment: Distribution, bioconcentration, and ecological risks

Field research on phthalate monoesters (MPEs) and their relationships with phthalate esters (PAEs) is limited, especially in wild fishes. Here, PAEs and MPEs were measured in surface water, sediment, and wild fish collected from a representative river basin with high economic development. Several metabolites of emerging plasticizers, such as mono(3,5,5-trimethyl-1-hexyl) phthalate and mono(6-oxo-2-propylheptyl) phthalate, have already existed in fish with high detection frequencies (95 % and 100 %). Monobutyl phthalate and mono(2-ethylhexyl) phthalate were the predominant MPEs in fish and natural environment (surface water and sediment), while bis(2-ethylhexyl) phthalate was the most abundant PAEs in all matrices. The total concentrations (median) of 9 PAEs and 16 MPEs were 5980 and 266 ng/L in water, 231 and 10.6 ng/g (dw) in sediment, and 209 and 32.5 ng/g (ww) in fish, respectively. The occurrence of MPEs was highly related to their parent PAEs, with similar spatial distribution characteristics in the aquatic environments. Moreover, municipal wastewater discharge was recognized as the main source of MPEs in the research area. Fish species can accumulate targeted chemicals, and it seems more MPEs were from the PAE degradation in fish other than the direct uptake of MPEs in water. Parent PAEs showed higher ecological risk than their corresponding metabolites.

Phthalate monoesters accumulation in residential indoor dust and influence factors

Phthalate monoesters (mPAEs) possess biological activity that matches or even exceeds that of their parent compounds, phthalate esters (PAEs), negatively impacting humans. Indoor dust is the main carrier of indoor pollutants. In this study, indoor dust samples were collected from 46 households in Changchun City, Jilin Province, in May 2019, and particulate and flocculent fibrous dust was used as the research target to analyze the concentration and compositional characteristics of mPAEs, primary metabolites of five significant PAEs. The influence of factors such as architectural features and living habits in residential areas on exposure to mPAEs was explored. Ten suspected enzyme genes along with two metabolic pathways with the ability to degrade PAEs were screened using PICRUSt2. The results showed that the total concentrations of the five mPAEs in the indoor dust samples were particulate dust (11.49-78.69 μg/g) and flocculent fibrous dust (21.61-72.63 μg/g), respectively. The molar concentration ratio (RC) of mPAEs to corresponding PAEs significantly differed among chemicals, with MMP/DMP and MEP/DEP sporting the highest RC values. Different bacterial types have shown distinct influences against mPAEs and PAEs. Enzyme function and metabolic pathway abundance had a significant effect on the concentration of some mPAEs, mPAEs are most likely derived from microbial degradation of PAEs.

Phthalate Biomarkers Composition in Relation to Fatty Liver: Evidence from Epidemiologic and in vivo studies

Phthalates, classified as environmental endocrine disruptors, pose potential toxicity risks to human health. Metabolic dysfunction-associated fatty liver disease is one of the most widespread liver diseases globally. Compared to studies focusing on metabolic disorders in relation to pollutants exposure, the impact of individual factors such as fatty liver on the in vivo metabolism of pollutants is always overlooked. Therefore, this study measured concentrations and composition of phthalate monoesters (mPAEs) in human urine samples, particularly those from fatty liver patients. Furthermore, we induced fatty liver in male Wistar rats by formulating a high-fat diet for twelve weeks. After administering a single dose of DEHP at 500 mg/kg bw through gavage, we compared the levels of di-2-ethylhexyl phthalate (DEHP), its metabolites (mDEHPs) and three hepatic metabolic enzymes, namely cytochrome P450 enzymes (CYP450), UDP glucuronosyltransferase 1 (UGT1), and carboxylesterase 1 (CarE1), between the normal and fatty liver rat groups. Compared to healthy individuals (n = 75), fatty liver patients (n = 104) exhibited significantly lower urinary concentrations of ∑mPAEs (median: 106 vs. 166 ng/mL), but with a higher proportion of mono-2-ethylhexyl phthalate in ∑mDEHPs (25.7 % vs. 9.9 %) (p < 0.05). In the animal experiment, we found that fatty liver in rats prolonged the elimination half-life of DEHP (24.61 h vs. 18.89 h) and increased the contents of CYP450, CarE1, and UGT1, implying the common but differentiated metabolism of DEHP as excess lipid accumulation in liver cells. This study provides valuable information on how to distinguish populations in biomonitoring studies across a diverse population and in assigning exposure classifications of phthalates or similar chemicals in epidemiologic studies.