Effect of aging on the release of di-(2-ethylhexyl) phthalate from biodegradable and petroleum-based microplastics into soil

Due to microplastics (MPs) being widely distributed in soil, the use of advanced oxidation to remediate organic-contaminated soils may accelerate the aging of MPs in soil and impact the release of di-(2-ethylhexyl) phthalate (DEHP), a potential carcinogen used as a plasticizer in plastics, from MPs. In this study, persulfate oxidation (PO) and temperature treatment (TT) were used to treat biodegradable and petroleum-based MPs, including polylactic acid (PLA), polyvinyl chloride (PVC), and polystyrene (PS). The methods used for evaluating the characteristics changes of MP were X-ray diffraction (XRD) analysis and water contact angle measurement. The effects of aging on DEHP release from MPs were investigated via soil incubation. The results showed PO and TT led to increased surface roughness, oxygen-containing functional group content, and hydrophilicity of the MPs with prolonged aging, consequently accelerating the release of DEHP from the MPs. Interestingly, PLA aged faster than PVC and PS under similar conditions. After 30 days of PO treatment, DEHP release from PLA into the soil increased 0.789-fold, exceeding the increase from PVC (0.454-fold) and PS (0.287-fold). This suggests that aged PLA poses a higher ecological risk than aged PVC or PS. Furthermore, PO treatment resulted in the oxidation and degradation of DEHP on the MP surface. After 30 days of PO treatment, the DEHP content in PLA, PVC, and PS decreased by 19.1%, 25.8%, and 23.5%, respectively. Specifying the types of MPs studied and the environmental conditions would provide a more precise context for the results. These findings provide novel insights into the fate of biodegradable and petroleum-based MPs and the potential ecotoxicity arising from advanced oxidation remediation in contaminated soils.

Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks

Microplastics (MPs) are known to act as carriers of heavy metals; however, little is known about the intrinsic chemical additives of MPs, such as hexabromocyclododecane (HBCD), in terms of the adsorption behaviors and migration risks of heavy metals on MPs. Here, we reported the potential mechanisms and risks of HBCD inherent in polystyrene (PS) MPs with Cu(II), Ni(II), and Zn(II) adsorption/desorption. A comparison of the adsorption capacity of the metals onto HBCD/PS composites (HBCD/PS) MPs (10.31-20.76 μmol/g), pure MPs (0-3.60 μmol/g), and natural minerals (0.11-13.88 μmol/g) showed that the addition of HBCD significantly promoted the metals adsorption onto the HBCD/PS MPs, and even exceeded that of natural particles. Isotherms and thermodynamic data suggested that the adsorption process of the metals onto the HBCD/PS MPs was spontaneous and endothermic, and that the adsorption was a mainly multi-ion process with an inclined direction. Furthermore, the results of SEM-EDS, FTIR, and XPS analyses, as well as density functional theory well explained that the metals were mainly adsorbed on the -O and -Br groups of the HBCD/PS MPs via electrostatic interactions and surface complexation. More importantly, by comparing the desorption activity with natural river water and seawater, HBCD inherent in MPs can enhance the long-range transfer of metals carried by the HBCD/PS MPs from contamination sources to potential sink like oceans. Thus, the HBCD/PS MPs with high loading of Cu(II), Ni(II), and Zn(II) could be potential secondary sources of these metals in seawater. Overall, these findings revealed the potential risks of flame retardant in MPs associated with metal migration, and advocated that flame retardant-related waste MPs should be included in coastal sustainable development.

Disentangling the influence of microplastics and their chemical additives on a model detritivore system

Microplastics (MPs) can negatively impact freshwater organisms via physical effects of the polymer itself and/or exposure to chemicals added to plastic during production to achieve desired characteristics. Effects on organisms may result from direct exposure to plastic particles and/or chemical additives or effects may manifest as indirect effects through ecological interactions between organisms (e.g., reduced food availability that impairs a consumer). To disentangle these issues, we used a simplified freshwater food web interaction comprising microbes and macroinvertebrate detritivores to evaluate the toxicity of 1) polyvinyl chloride (PVC) MPs without added chemicals (virgin), 2) the common chemical additive dibutyl phthalate (DBP), and 3) PVC MPs with incorporated DBP. Exposure to virgin PVC MPs (0.33 and 3.3 mg/L) caused negligible ecological effect with the exception of reduced macroinvertebrate feeding rates at 3.3 mg/L. Exposure to DBP (1 mg/L) both individually and when incorporated into the PVC MPs negatively impacted all tested endpoints, including microbial and macroinvertebrate respiration, feeding rate and assimilation efficiency. DBP leached rapidly from the MPs into the water, and also accumulated in macroinvertebrates and their food, providing multiple routes of exposure. Our findings suggest that additives which are intentionally incorporated into MPs could play a key role in MP toxicity and contribute to the disruption of key ecological interactions underpinning ecosystem processes, such as leaf litter decomposition.

Disposable plastic materials release microplastics and harmful substances in hot water

The boom in the takeaway industry has significantly increased the consumption of disposable plastic materials, which are very likely to release microplastic particles and cause secondary risks during daily use. The objective of this study was to probe whether heat treatment of disposable plastic materials in water, mimicking their use for hot food or drink, could result in the release of particles and harmful substances in the leachate. Our results showed that a hot water (100 °C) soaking released 1.07 ± 0.507, 1.44 ± 0.147, 2.24 ± 0.719 and 1.57 ± 0.599 million submicron and microparticles/mL from plastic packaging, cups, transparent boxes and expandable boxes, respectively after 60 min of agitation, and the submicron fraction was dominant. Based on Fourier transform infrared spectroscopy, heat treatment also altered the chemical composition of polyethylene packaging, but it had minor effects on polypropylene cups, transparent boxes and polystyrene expandable boxes. In addition, organic chemicals and heavy metals (mainly As, Cr and Pb), with maximum concentrations of 2.1 ± 0.85 mgC/L and 4.2 ± 0.32 ng/L, were detected in the leachate from plastic packaging, cups and expandable boxes, indicating the potential risk of these materials while holding hot food or drink. The findings suggest the potential ingestion risk of microplastics and harmful substances by human beings during the daily use of disposable plastic materials.

Microplastics altered soil microbiome and nitrogen cycling: The role of phthalate plasticizer

Microplastics are emerging contaminants that are increasingly detected in soil environment, but their impact on soil microbiota and related biogeochemical processes remains poorly understood. In particular, the mechanisms involved (e.g., the role of chemical additives) are still elusive. In this study, we found that plasticizer-containing polyvinyl chloride (PVC) microplastics at 0.5% (w/w) significantly increased soil NH₄⁺-N content and decreased NO₃^--N content by up to 91%, and shaped soil microbiota into a microbial system with more nitrogen-fixing microorganisms (as indicated by nifDHK gene abundance), urea decomposers (ureABC genes and urease activity) and nitrate reducers (nasA, NR, NIT-6 and napAB genes), and less nitrifiers (amoC gene and potential nitrification rate). Exposure to plasticizer alone had a similar effect on soil nitrogen parameters but microplastics of pure PVC polymer (either granule or film) had little effect over 60 days, indicating that phthalate plasticizer released from microplastics was the main driver of effects observed. Furthermore, a direct link between phthalate plasticizer, microbial taxonomic changes and altered nitrogen metabolism was established by the isolation of phthalate-degrading bacteria involved in nitrogen cycling. This study highlights the importance of chemical additives in determining the interplay of microplastics with microbes and nutrient cycling, which needs to be considered in future studies.

Human health impacts of exposure to phthalate plasticizers: An overview of reviews

In this review of reviews, we overview the current global body of available evidence from structured reviews of epidemiological studies that explore human health outcomes associated with exposure to phthalates (chemical plasticisers commonly found in plastics). We found robust evidence for an association with lower semen quality, neurodevelopment and risk of childhood asthma, and moderate to robust evidence for impact on anogenital distance in boys. We identified moderate evidence for an association between phthalates/metabolites and low birthweight, endometriosis, decreased testosterone, ADHD, Type 2 diabetes and breast/uterine cancer. There was some evidence for other outcomes including anofourchette distance, fetal sex hormones, pre-term birth, lower antral follicle count, reduced oestrodiol, autism, obesity, thyroid function and hearing disorders. We found no reviews of epidemiological human studies on the impact of phthalates from recycled plastics on human health. We recommend that future research should use urine samples as exposure measures, consider confounders in analyses and measure impacts on female reproductive systems. Our findings align with emerging research indicating that health risks can occur at exposure levels below the "safe dose" levels set out by regulators, and are of particular concern given potential additive or synergistic "cocktail effects" of chemicals. This raises important policy and regulatory issues for identifying and controlling plastics and health related impacts and highlights a need for more research into substances of concern entering plastics waste streams via recycling.

Dibutyl phthalate release from polyvinyl chloride microplastics: Influence of plastic properties and environmental factors

In recent years, great efforts have been made to understand the capacity of microplastics to adsorb environmental pollutants; however, relatively little is known about the ability of microplastics to release inherent additives into peripheral environments. In this study, we investigated the leaching behavior of phthalate plasticizer from polyvinyl chloride (PVC) microplastics, in aqueous solutions relevant to aquatic and soil environments. It was found that plastic properties, such as particle size, plasticizer content and aging of plastics had a great effect on the leaching of dibutyl phthalate (DnBP). Phthalate release was generally higher in smaller particles and particles with higher phthalate content. Whereas, plastic aging caused by solar irradiation could either enhance phthalate release by increasing plastic hydrophilicity or decrease the leaching by reducing readily available fractions of phthalate. Regarding environmental factors, solution pH (3-9) and ionic strength (0-0.2 M NaCl) were found to have minor effect on phthalate release, while fulvic acid (0-200 mg/L) greatly promoted the release by improving phthalate solubility and solution-plastic affinity. Interestingly, we found that more DnBP was leached out when fulvic acid and NaCl coexisted, and the results from dissolved organic carbon (DOC) and three-dimensional fluorescence spectroscopy analyzes suggested that the leaching of other fulvic acid-like additives might have played a role. These findings would be helpful for predicting the potential of microplastics to release toxic additives under different environmental conditions.

Factors affecting the quality of therapeutic proteins in recombinant Chinese hamster ovary cell culture

Chinese hamster ovary (CHO) cells are the most widely used mammalian host cells for the commercial production of therapeutic proteins. Fed-batch culture is widely used to produce therapeutic proteins, including monoclonal antibodies, because of its operational simplicity and high product titer. Despite technical advances in the development of culture media and cell cultures, it is still challenging to maintain high productivity in fed-batch cultures while also ensuring good product quality. In this review, factors that affect the quality attributes of therapeutic proteins in recombinant CHO (rCHO) cell culture, such as glycosylation, charge variation, aggregation, and degradation, are summarized and categorized into three groups: culture environments, chemical additives, and host cell proteins accumulated in culture supernatants. Understanding the factors that influence the therapeutic protein quality in rCHO cell culture will facilitate the development of large-scale, high-yield fed-batch culture processes for the production of high-quality therapeutic proteins.

Interaction, transformation and toxicity assessment of particles and additives used in the semiconducting industry

Chemical mechanical planarization (CMP) is a widely used technique for the manufacturing of integrated circuit chips in the semiconductor industry. The process generates large amounts of waste containing engineered particles, chemical additives, and chemo-mechanically removed compounds. The environmental and health effects associated with the release of CMP materials are largely unknown and have recently become of significant concern. Using a zebrafish embryo assay, we established toxicity profiles of individual CMP particle abrasives (SiO₂ and CeO₂), chemical additives (hydrogen peroxide, proline, glycine, nicotinic acid, and benzotriazole), as well as three model representative slurries and their resulting waste. These materials were characterized before and after use in a typical CMP process in order to assess changes that may affect their toxicological profile and alter their surface chemistry due to polishing. Toxicity outcome in zebrafish is discussed in relation with the physicochemical characteristics of the abrasive particles and with the type and concentration profile of the slurry components pre and post-polishing, as well as the interactions between particle abrasives and additives. This work provides toxicological information of realistic CMP slurries and their polishing waste, and can be used as a guideline to predict the impact of these materials in the environment.

On-Line two dimensional liquid chromatography based on skeleton type molecularly imprinted column for selective determination of sulfonylurea additive in Chinese patent medicines or functional foods

Substandard and counterfeit anti-diabetic medicines directly influence the health and impose a great danger to individual patients and to public health. Counterfeiting has become a serious and underreported problem in the pharmaceutical industry. There are a large number of counterfeit medicines flooded in anti-diabetic markets which effect human health directly and indirectly. Therefore, some novel analytical techniques are necessary to be established for detecting these counterfeit drugs. In this study, a novel skeleton type molecularly imprinted column was successfully prepared. Based on the column, a simple, fast and reliable two-dimensional chromatography analytical system was established for selective determination of the illegal sulfonylurea additive in traditional Chinese patent medicines and functional foods. The developed method was validated. The linearitiesof the method were tested with calibration curves using ten calibration points in the concentration range of 0.25-12.5μg/g. The LODs were 0.0125μg/g and 0.01μg/g for tolbutamide and glibenclamide respectively. The five batches of Chinese patent medicines and dietary supplements obtained from different markets and online websites were tested by the validated method. With good retention time and spectral confirmation, chemical anti-diabetic substances were identified and quantified in traditional Chinese medicine and in dietary supplements.