Are "liquid plastics" a new environmental threat? The case of polyvinyl alcohol

Transgenerational effects of water-soluble polymers on Daphnia magna at environmentally relevant concentrations: The role of multigenerational plasticity

The widespread use of water-soluble polymers (WSPs) like polyethylene glycol (PEG) and polyvinyl alcohol (PVA) across multiple industrial and household uses has recently raised concerns about their environmental persistence and potential toxicity to aquatic organisms. Despite being excluded from regulatory oversight, recent studies suggest possible ecological risks associated with sub-lethal exposures to these polymers. In this context, this study investigates the transgenerational effects of PEG and PVA on Daphnia magna, focusing on both life-history parameters and epigenetic modifications at the environmentally relevant concentration of 1 μg/L. Through continuous exposure experiments, spanning three generations (from F0 to F3), and "recovery" groups, where only the parental generation (F0) was exposed, our results reveal significant reductions in the number of newborns and reproductive parameters in the F0 generation exposed to PEG but not in subsequent generations. This suggests a multigenerational plasticity in Daphnia through a compensatory or acclimation reproductive response over time. Global cytosine methylation patterns also showed a significant initial increase in the F0 generation exposed to PEG, which decreased in later generations, indicating a possible epigenetic mechanism underlying observed reproductive effects. In contrast, PVA exhibited no significant changes in both life history parameters and methylation but showed a global methylation trend suggesting its likely epigenetic influence. These findings underscore the need for comprehensive risk assessments of WSPs, particularly their potential for inducing long-term (epigenetic) effects, influencing reproductive functions across generations and how increased plasticity may affect responses against novel other stressors.

Emissions of water-soluble polymers from household products to the environment: a prioritization study

Water-soluble polymers (WSPs) are widely used in household products, including cleaning and personal care products. However, unlike insoluble plastic polymers, the environmental risks of WSPs are poorly understood. This study was performed to identify polymers in household use and characterize their emissions to the environment and key data gaps for prioritization. An inventory of polymers was developed and these were broadly grouped based on structure. Information from patents was combined with literature data to estimate down-the-drain emissions for each polymer. For the polymers with the highest emissions, predicted environmental concentrations for surface water and soil were estimated. A total of 339 individual polymers were identified and categorized into 26 groups. The polymers with the highest down-the-drain emissions were sodium laureth sulfate (1.6-3.4 g capita-1 day-1), styrene/acrylates copolymer (0.1-0.8 g capita-1 day-1), and monoethanolamine-laureth sulfate (0.4-0.8 g capita-1 day-1). An analysis of available fate and ecotoxicity data for 30 key high-emission polymers indicated that several are lacking in data. In particular, no data were found for styrene/acrylates copolymer and copolymer of polyethylene glycol/vinyl acetate, and the environmental fate of polyquaterniums and polyol ethoxylate esters has been understudied, particularly in light of their hazard potential. However, a lack of reporting of key polymer properties hinders analysis. We recommend increased transparency in reporting of polymer identities moving forward as well as experimental work determining fate, removal, and hazard of the prioritized high-emission polymers that are lacking in data.

Environmental concerns on water-soluble and biodegradable plastics and their applications - A review

Water-soluble polymers are materials rapidly growing in volume and in number of materials and applications. Examples include synthetic plastics such as polyacrylamide, polyacrylic acid, polyethylene glycol, polyethylene oxide and polyvinyl alcohol, with applications ranging from cosmetics and paints to water purification, pharmaceutics and food packaging. Despite their abundance, their environmental concerns (e.g., bioaccumulation, toxicity, and persistence) are still not sufficiently assessed, especially since water soluble plastics are often not biodegradable, due to their chemical structure. This review aims to overview the most important water-soluble and biodegradable polymers, their applications, and their environmental impact. Degradation products from water-insoluble polymers designed for biodegradation can also be water soluble. Most water-soluble plastics are not immediately harmful for humans and the environment, but the degradation products are sometimes more hazardous, e.g. for polyacrylamide. An increased use of water-soluble plastics could also introduce unanticipated environmental hazards. Therefore, excessive use of water-soluble plastics in applications where they can enter the environment should be discouraged. Often the plastics can be omitted or replaced by natural polymers with lower risks. It is recommended to include non-biodegradable water-soluble plastics in regulations for microplastics, to make risk assessments for different water-soluble plastics and to develop labels for flushable materials.

The effects of disturbance on hypothalamus-pituitary-thyroid axis in zebrafish larvae after exposure to polyvinyl alcohol

In recent years, considerable concerns have been raised regarding environmental pollution caused by water-soluble polymers (WSPs). Polyvinyl alcohol (PVA), used in the textile industry and in the manufacture of medical consumables, is one type of WSPs. After use, PVA is discharged and enters aquatic ecosystems, but most of it cannot be completely biodegraded in the environment. In this study, we investigated the effects of PVA on developmental toxicity and thyroid endocrine disruption using a zebrafish (Danio rerio) model. We treated zebrafish embryos with 10 g/L and 5 mg/L PVA for 96 h and found that the proportion of coagulated embryos significantly increased, resulting in a remarkable decrease in hatching rate and larval survival. The body length of zebrafish larvae in the exposed group was remarkably shorter than that of the control group (Control: 3.64 ± 0.03 mm vs. 10 g/L PVA: 3.46 ± 0.03 mm; p=0.001). Compared to the control group, the levels of T3 and T4 in embryos of the exposed group were significantly lower, while thyroid stimulating hormone (TSH) levels were significantly increased. Notable up-regulation of trh, tshβ, and tshr genes, as well as down-regulation of trα , tg, ttr, dio1, and dio2 genes, were observed in embryos of the exposed group. Collectively, these findings suggest that PVA negatively influences the development and function of the thyroid gland during zebrafish embryogenesis. These effects may be partly attributed to the disruption of hypothalamic-pituitary-thyroid (HPT) axis regulation. Therefore, raising awareness about the possible thyroid toxicity associated with PVA is crucial.

Behind conventional (micro)plastics: An ecotoxicological characterization of aqueous suspensions from End-of-Life Tire particles

Million tons of tires become waste every year, and the so-called End-of-Life Tires (ELTs) are ground into powder (ELT-dp; size < 0.8 mm) and granules (ELT-dg; 0.8 < size < 2.5 mm) for recycling. The aim of this study was to evaluate the sub-lethal effects of three different concentrations (0.1, 1, and 10 mg/L) of aqueous suspensions from ELT-dp and ELT-dg on Danio rerio (zebrafish) larvae exposed from 0 to 120 h post-fertilization (hpf). Chronic effects were assessed through biomarkers, real-time PCR, and proteomics. We observed a significant increase in swimming behavior and heart rate only in specimens exposed to ELT-dp suspensions at 1 and 10 mg/L, respectively. Conversely, the activities of detoxifying enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) showed significant modulation only in specimens exposed to ELT-dg groups. Although no effects were observed through real-time PCR, proteomics highlighted alterations induced by the three ELT-dp concentrations in over 100 proteins involved in metabolic pathways of aromatic and nitrogen compounds. The results obtained suggest that the toxic mechanism of action (MoA) of ELT suspensions is mainly associated with the induction of effects by released chemicals in water, with a higher toxicity of ELT-dp compared to ELT-dg.

Toxicity of water-soluble polymers polyethylene glycol and polyvinyl alcohol for fish and frog embryos

Personal Care Products (PCPs) have been one of the most studied chemicals in the last twenty years since they were identified as pseudo-persistent pollutants by the European Union in the early 2000s. The accumulation of PCPs in the aquatic environment and their effects on non-target species make it necessary to find new, less harmful, substances. Polyethylene glycol (PEGs) and polyvinyl alcohol (PVAs) are two polymers that have increased their presence in the composition of PCPs in recent years, but little is known about the effect of their accumulation in the environment on non-target species. Through embryotoxicity tests on two common models of aquatic organisms (Danio rerio and Xenopus laevis), this work aims to increase the knowledge of PEGs and PVAs' effects on non-target species. Animals were exposed to the pollutant for 96 h. The main embryotoxicity endpoint (mortality, hatching, malformations, heartbeat rate) was recorded every 24 h. The most significant results were hatching delay in Danio rerio exposed to both chemicals, in malformations (oedema, body malformations, changes in pigmentation and deformations of spine and tail) in D. rerio and X. laevis and significant change in the heartbeat rate (decrease or increase in the rate) in both animals for all chemicals tested.

Ecotoxicity evaluation using the avoidance response of the oribatid mite Oppia nitens (Acari: Oribatida) in bioplastics, microplastics, and contaminated Superfund field sites

Bioplastics are considered sustainable alternatives to conventional microplastics which are recognized as a threat to terrestrial ecosystems. However, little is known about the potential ecotoxicological effects of bioplastics on soil fauna and ecosystems. The present study assessed the toxicity of microplastics [Polystyrene (PS), Polyethylene (PE)] and bioplastics [Polyvinyl alcohol (PVA), Sodium polyacrylate (NaPa) on a key soil fauna Oppia nitens, a soil oribatid mite, and investigated the ecological relevance of O. nitens avoidance response as a valuable tool for the risk assessment of contaminated soils such as the Superfund sites. Findings showed that the mites' net response indicated avoidance behavior such that in most cases as concentrations of micro- and bioplastics increased, so did the avoidance responses. The avoidance EC50 endpoints showed PS < PE < PVA < NaPa, indicating higher deleterious effects of microplastics. High toxicity of PS in soils to O. nitens at EC50 of 165 (±25) mg/kg compared to bioplastics and other known contaminants poses an enormous threat to soil. For bioplastics in this study, there were no significant avoidances at concentrations up to 16,200 mg/kg compared to PS and PE which showed avoidance responses at 300 and 9000 mg/kg respectively, implying that bioplastics might be relatively safer to soil mites compared to conventional microplastics. Also, results indicated that long-term heavy metal pollution such as in contaminated Superfund sites decreased microbial biomass; a useful bioindicator of soil pollution. Furthermore, O. nitens avoidance of heavy metals contaminated sites demonstrated the ecological relevance of avoidance response test when assessing the habitat integrity of contaminated soil. The present study further supports the inclusion of the oribatid mite, O. nitens in the ecological risk assessment of contaminants in soil.

Unveiling the multilevel impact of four water-soluble polymers on Daphnia magna: From proteome to behaviour (a case study)

The ubiquitous presence of water-soluble polymers (WSPs) in freshwater environments raises concerns regarding potential threats to aquatic organisms. This study investigated, for the first time, the effects of widely used WSPs -polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), and polyethylene glycol (PEG)- using a multi-level approach in the freshwater biological model Daphnia magna. This integrated assessment employed a suite of biomarkers, evaluation of swimming behaviour, and proteomic analysis to investigate the effects of three environmentally relevant concentrations (0.001, 0.5, and 1 mg/L) of the tested WSPs from molecular to organismal levels, assessing both acute and chronic effects. Our findings reveal that exposure to different WSPs induces specific responses at each biological level, with PEG being the only WSP inducing lethal effects at 0.5 mg/L. At the physiological level, although all WSPs impacted both swimming performance and heart rate of D. magna specimens, PAA exhibited the greatest effects on the measured behavioural parameters. Furthermore, proteomic analyses demonstrated altered protein profiles following exposure to all WSPs, with PVA emerging as the most effective.

Assessment of the impact of microplastic ingestion in striped red mullets from an Eastern Mediterranean coastal area (Zakynthos Island, Ionian Sea)

Monitoring microplastics (MPs) in the marine environment is an ongoing process, and our understanding of their impact on marine organisms is limited. The present study evaluates the effects of ingested MPs on the marine MP pollution bioindicator fish species Mullus surmuletus. The study follows a three-fold approach to assess the impact of MPs on marine organisms by investigating: 1) the ingestion of MPs, 2) the bioaccumulation of phthalate compounds as plastic additives, and 3) the evaluation of toxicological biochemical and cellular biomarkers. Striped red mullets were sampled in the marine protected area (MPA) of the National Marine Park of Zakynthos and coastal sites with high touristic pressure in Zakynthos Island in the Ionian Sea, Greece. Fewer ingested MPs and lower phthalate concentrations were found in fish inside the MPA compared to those sampled outside the marine park. However, no relationship was found between either phthalate concentrations or biomarker levels with the ingested MPs in the red striped mullets. Biomarker levels were influenced by season and site, but no effect could be attributed to the ingested MPs. The lack of association of biomarker responses and plasticizer bioaccumulation to MP ingestion can be explained by the low number of ingested MPs in the fish from Zakynthos coastal area as MP abundance ranged from 0.15 to 0.55 items per individual fish.

Simultaneous identification and quantification of three water-soluble polymers (PVP, PNVCL and PEI) in wastewater samples by continuous-flow off-line pyrolysis GC/MS

In environmental analysis, the detection of water-soluble synthetic polymers (WSSP) presents considerable challenges. Thus, a precise and reproducible analytical method was developed using continuous-flow off-line pyrolysis with gas chromatography/mass spectrometry (GC/MS) to simultaneously identify multiple water-soluble polymers from a single environmental sample. WSSP are widely used in multiple industries as hydrogels due to their hydrophilic character and potential biocompatibility. This adaptability of hydrogels is reflected in their ability to provide customized formulations for specific needs, such as in the development of personal care products, medicine, and pharmaceuticals. Specifically, polyvinylpyrrolidone (PVP), poly(N-vinylcaprolactam) (PNVCL), and polyethyleneimine (PEI) were targeted for analysis in wastewater, employing unique pyrolysis products for identification. These polymers require careful assessment in wastewater to evaluate potential environmental risks associated with their release. PVP and PNVCL were identified through two pyrolysis products, while six pyrolysis products were utilized for the identification of PEI. The validated method demonstrated very good linearity and reproducibility, with correlation coefficients ranging from 0.94 to 0.99 and relative standard deviation (RSD) values between 3 % and 36 % for the targeted compounds. The limit of quantification (LOQ) for the three polymers ranged from 1 to 10 μg L-1. Moreover, the average recovery rates for these polymers, determined from artificial water samples, were approx. 85 %. Utilizing the validated method, water samples from seven wastewater treatment plants in Germany were successfully analyzed, confirming the presence of these polymers at elevated concentrations in the μg L-1 range. Notably, untreated influent waters exhibited higher polymer levels compared to treated influents and effluents, underscoring their significant contribution to overall polymer content. The developed analytical method provides an efficient tool for the simultaneous identification and quantification of PVP, PNVCL, and PEI in wastewater samples. The results highlighted the prevalent presence of PVP, PNVCL, and PEI in the tested wastewater samples, indicating their significant abundance.

A class of their own? Water-soluble polymer pollution impacting a freshwater host-pathogen system

While the inclusion of synthetic polymers such as primary microplastics within personal care products have been widely restricted under EU/UK Law, water-soluble polymers (WSPs) have so far slipped the net of global chemical regulation despite evidence that these could be polluting wastewater effluents at concentrations greatly exceeding those of microplastics. Polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) represent WSPs with common industry and household uses, down-the-drain disposal and a direct route to wastewater treatment plants, conveying high risk of environmental leaching into freshwater ecosystems. The current study is the first investigating the impacts of predicted environmental concentrations of these WSPs on life-history traits of two freshwater species also constituting a disease model (fish - Poecilia reticulata and parasite - Gyrodactylus turnbulli). Single effects of WSPs on fish as well as their interactive effects with infection of the ectoparasite were determined over a 45-day exposure. Generally, WSPs reduced fish growth and increased routine metabolic rate of fish implying a depleted energetic budget, however these effects were dose, exposure time and polymer dependent. Parasitic infection alone caused a significant reduction in fish growth and enhanced fish routine metabolic rate. In contrast, a non-additive effect on metabolic rate was evident in fish experiencing simultaneous infection and WSP exposure, suggesting a protective effect of the two WSPs for fish also exposed to a metazoan ectoparasite. Off-host parasite survival was significantly lowered by both WSPs; however, parasite counts of infected fish also exposed to WSP were not significantly different from the control, implying more complex mechanisms may underpin this stressor interaction. Distinct detrimental impacts were inflicted on both organisms implying environmental leaching of WSPs may be causing significant disruption to interspecies interactions within freshwater ecosystems. Additionally, these results could contribute to sustainable development in industry, as we conclude PVA represents a less harmful alternative to PVP.

To be or not to be plastics? Protein modulation and biochemical effects in zebrafish embryos exposed to three water-soluble polymers

Water-soluble polymers (WSPs) are a particular category of polymers that, due to their capability to be soluble in water, come out of the classic definition of plastic and therefore also from its regulation and control, representing a possible new environmental problem considering the number of consumer products in which they are contained. For this reason, the aim of this study was to evaluate the possible adverse effects of three of the most used WSPs (polyacrylic acid - PAA, polyethylene glycol - PEG, polyvinylpyrrolidone - PVP), administered at relevant environmental concentrations (0.001, 0.5 and 1 mg/L) to Danio rerio (zebrafish) embryos up to 120 h post fertilization. To assess the WSP toxicity at the molecular, cellular and organism level we used an integrated ecotoxicological approach of both biomarkers and high-throughput technology based on gel-free proteomics. The main results showed how all the three WSPs up-regulated many proteins (up to 74 in specimens exposed to 1 mg/L PVP) with a wide range of molecular functions and involved in numerous cellular pathways of exposed specimens. On the other hand, the measurement of biomarkers showed how PAA and PVP were able to activate the antioxidant machinery following an over-production of reactive oxygen species, while PEG produced no significant changes in the biomarkers measured. Based on the obtained results, the use and application of WSPs should be revised and regulated.

Evaluation of nuclear magnetic resonance spectroscopy for characterisation and quantitation of water-soluble polymers in river water

Water-soluble polymers (WSPs) are commonly used in industrial, commercial, agricultural and pharmaceutical products and their molecular weights and concentrations vary considerably. Methods commonly used in the analysis of WSPs are often for pure products or formulations with only a few other high MW constituents. These methods, like size exclusion chromatography (SEC) or Gel Permeation Chromatography coupled with Mass Spectrometry (MS) can be frustrated by the impact of the necessary separation steps prior to identification and the limitations of MS when identifying and quantifying polymers. To that end, the employment of a Nuclear Magnetic Resonance (NMR) method to identify, characterize and quantify WSPs in the real-world is reported for the first time. Samples were taken from fourteen UK inland river sites, concentrated via air-drying, freeze-drying or vacuum-drying and analyzed using 1D 1H NMR and 2D 1H Diffusion Ordered Spectroscopy (DOSY) NMR analysis. Seven of the river sites showed the presence of polyethylene glycol (PEG) with a range of molecular weights, evidencing the application of these techniques in analysis of WSPs. Soil percolation models evidenced the proof of principle that these techniques can also be used for the detection of polyacrylamide (PAM) and polyacrylic acid (PAA). This work should better enable the evaluation of the biological impact of WSPs on aquatic organisms in future studies.

Recent innovations and challenges in the eradication of emerging contaminants from aquatic systems

Presence of emerging pollutants (EPs), aka Micropollutants (MPs) in the freshwater environments is a severe threat to the environment and human beings. They include pharmaceuticals, insecticides, industrial chemicals, natural hormones, and personal care items and the pollutants are mostly present in wastewater generated from urbanization and increased industrial growth. Even concentrations as low as ngL^-1 or mgL^-1 have proven ecologically lethal to aquatic biota. For several years, the biodegradation of various Micropollutants (MPs) in aquatic ecosystems has been a significant area of research worldwide, with many chemical compounds being discovered in various water bodies. As aquatic biota spends most of their formative phases in polluted water, the impacts on aquatic biota are obvious, indicating that the environmental danger is substantial. In contrast, the impact of these contaminants on aquatic creatures and freshwater consumption is more subtle and manifests directly when disrupting the endocrine system. Research and development activities are expected to enable the development of ecologically sustainable, cost-effective, and efficient treatments for practical systems in the near future. Therefore, this review aims to understand recent emerging pollutants discovered and the available treatment technologies and suggest an innovative and cost-effective method to treat these EPs, which is sustainable and follows the circular bioeconomy.

Water-Soluble Synthetic Polymers: Their Environmental Emission Relevant Usage, Transport and Transformation, Persistence, and Toxicity

Water-soluble synthetic polymers (WSPs) are distinct from insoluble plastic particles, which are both critical components of synthetic polymers. In the history of human-made macromolecules, WSPs have consistently portrayed a crucial role and served as the ingredients of a variety of products (e.g., flocculants, thickeners, solubilizers, surfactants, etc.) commonly used in human society. However, the environmental exposures and risks of WSPs with different functions remain poorly understood. This paper provides a critical review of the usage, environmental fate, environmental persistence, and biological consequences of multiple types of WSPs in commercial and industrial production. Investigations have identified a wide market of applications and potential environmental threats of various types of WSPs, but we still lack the suitable assessment tools. The effects of physicochemical properties and environmental factors on the environmental distribution as well as the transport and transformation of WSPs are further summarized. Evidence regarding the degradation of WSPs, including mechanical, thermal, hydrolytic, photoinduced, and biological degradation is summarized, and their environmental persistence is discussed. The toxicity data show that some WSPs can cause adverse effects on aquatic species and microbial communities through intrinsic toxicity and physical hazards. This review may serve as a guide for environmental risk assessment to help develop a sustainable path for WSP management.

Plastic ingestion by carnivore fish in a neotropical floodplain: seasonal and interspecific variations

Some studies have shown that freshwater ecosystems are polluted in a similar proportion to marine ecosystems; however, there are many gaps to be filled in this topic. Here, we investigated whether plastics were consumed by carnivore fishes in a Neotropical floodplain and whether it was connected to seasonality (dry and wet seasons). We also evaluated the association between each type of plastic and the fish species. We analyzed the gastrointestinal contents of 23 species and assessed the occurrence and number of plastic particles. Plastics were obtained through chemical digestion and the spectrum of each sample, using a FT-IR imaging microscope. We performed a correspondence analysis (CA) with plastic data to assess the relationship between each type of plastic and the fish species. We also performed linear regression models to assess the relationships of occurrence and number of plastics ingested with seasonality. Nine species had plastics in their gastrointestinal contents, and they were identified as polyvinyl alcohol (PVA), polyamide (PA), polyethylene (PE), polystyrene (PS), and polypropylene (PP). The number of plastics had a positive relationship with the wet season, while the occurrence did not show a significant relationship with any season. These results are particularly important when considering the socioeconomic relevance and the ecological importance of this trophic guild.