Pollution characteristics and health risk assessment of arsenic transformed from feed additive organoarsenicals around chicken farms on the North China Plain

Mass spectrometry analysis of PM2.5 in poultry farms and the cytotoxicity and metabolism perturbation of BEAS-2B cells

To evaluate the potential risks posed by farm-derived fine particulate matter (PM2.5), we conducted a comprehensive analysis of PM2.5 samples collected from chicken farms. Specifically, water-soluble ions, metal and metalloids, and volatile organic compounds (VOCs) were quantitatively determined via ion chromatography, inductively coupled plasma mass spectrometry (ICP-MS), and gas chromatography‒mass spectrometry (GC‒MS), respectively. Furthermore, the microbial composition was elucidated through 16S ribosomal RNA (rRNA) high-throughput sequencing and ribosomal DNA (rDNA)-internal transcribed spacer (ITS) analysis. The study revealed that the water-soluble ion profile of PM2.5 was dominated by NO3-, NH4+, and SO42-, among others. Notably, aluminum, zinc, and manganese emerged as metals with relatively high concentrations. The primary VOCs identified were formic acid, acetic acid, and propionic acid. Microbiologically, Aspergillus and Faecalibacterium were the predominant genera detected. Upon exposure to PM2.5, BEAS-2B cells exhibited marked morphological alterations and a decrease in cell viability. Additionally, a dose-dependent increase in intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels was observed, accompanied by a decrease in superoxide dismutase (SOD) activity. This oxidative stress was further corroborated by elevated levels of inflammatory cytokines, including IL-6, IL-8, and TNF-α. Our findings suggest that livestock-generated PM2.5 significantly impacts cellular metabolism, particularly amino acid and nucleotide metabolism. Notably, PM2.5 from these environments can elicit cellular oxidative stress and inflammatory responses, which, with prolonged exposure, may lead to adverse health outcomes in both animals and humans. Therefore, the physical, chemical, and microbial characteristics of PM2.5 in poultry farms cannot be overlooked, emphasizing the critical need to improve the air quality within these facilities.

Residual heavy metals and antibiotic pollution in abandoned breeding areas along the northeast coast of Hainan Island, China

To assess the environmental status of an abandoned aquaculture and breeding area in the northeast coast of the Hainan Island, surface and well water, sediment and surface soils were sampled and analyzed for conventional physicochemical properties, heavy metals and antibiotics. Metagenome tests were also conducted to determine the composition and diversity of the microbial community in typical habitats. Affected by the discharge of wastewater from higher-place pond aquaculture, coastal freshwater rivers have undergone significant salinization, Cl- and Na+ were as high as 4.51 × 103 and 1.42 × 103 mg/L. The 3 hand-pumped wells surveyed were also suffered from varying degrees of salinization and heavy metal pollution, especially the threat of arsenic pollution. Compared with the local background values, significantly higher valves of Cu, Zn, As and Cd were observed in the surface soil and sediment, and the average concentrations for Cu, Zn, As and Cd are 5.71, 17.6, 15.4 and 0.09 mg/kg respectively. For As，the Nemerow index ranges from 7 to 16 and the geoaccumulation index is between 2 and 4, indicating moderate to severe pollution levels in surface soil. 14 antibiotics were detected in the soil and sediment samples, and the highest total amount was 73 μg/kg, with tetracycline being the dominant antibiotic. Sediment and forest soil showed different microbial community and the genetic diversity index of sediment was lower than that of the forest soils. For typical vegetation soil, the genetic diversity followed the order as P. elliottii × P. caribaea > Eucalyptus > C. equisetifolia. Among the soil and sediment samples, the highest abundances of antibiotic resistance genes (ARGs) were associated with elfamycin, peptide, rifamycin, and the most common antibiotic resistance mechanisms were antibiotic target alteration (54.5 %), antibiotic efflux (27.6 %) and antibiotic target replacement (12.1 %). The metal resistance genes (MRGs) for Cu, Fe, and Zn resistance were the main MRGs in the samples. This study identified the potential ecological environment risk factors in the abandoned coastal breeding areas, and suggested continuous monitoring and assessment of the residual pollutant abatement processes in the future.

The Role of the cGAS/STING Pathway in Arsenic-Induced Neurotoxicity: Insights from the Crosstalk Between Astrocytes and Neurons

Arsenic is a detrimental environmental toxicant linked to neurological damage; however, the mechanisms involved remain incompletely understood. Chronic proinflammatory responses are thought to play a central role in arsenic-induced neurotoxicity. Astrocytes, which are the predominant glial cells in the central nervous system (CNS), release significant amounts of proinflammatory cytokines upon overactivation. However, the molecular mechanisms driving this response remain to be elucidated. This study aimed to elucidate the mechanisms underlying arsenic-induced astrocyte activation and the subsequent neuronal damage, both in vivo and in vitro. In a rat model of arsenic exposure, significant neuropathological damage was detected in the CA3 region of the hippocampus. Specifically, markers of astrocyte activation, such as glial fibrillary acidic protein (GFAP) and inducible nitric oxide synthase (iNOS), as well as the inflammatory cytokine interleukin (IL)-1β, were significantly upregulated, and apoptosis was markedly increased, indicating neurotoxic damage. Furthermore, in vitro experiments revealed that arsenic exposure induced substantial upregulation of cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING), GFAP, iNOS, and IL-1β in astrocytes, accompanied by an increase in IL-1β secretion into the culture supernatant. In addition, co-culturing neurons with conditioned medium from arsenic-exposed astrocytes resulted in significant neuronal apoptosis. Importantly, the cGAS-STING pathway inhibitor H-151 effectively suppressed the arsenic-induced astrocyte activation and IL-1β secretion, while also reducing neuronal apoptosis in the conditioned medium. Collectively, these results indicate that arsenic exposure activates the cGAS-STING signaling pathway in astrocytes, enhancing proinflammatory activation and IL-1β expression, which in turn mediates neuronal apoptosis, representing a critical mechanism underlying arsenic-induced neurotoxicity.

A Recombinant Lentiviral Vegfr2-Silencing Vector Attenuates Roxarsone-Promoted Growth of Rat Vascular Endothelial Cells and Angiogenesis in Matrigel Plug and B16F10 Xenograft Models

Roxarsone (ROX) is widely used as a feed addictive for livestock and poultry. ROX promotes angiogenesis, which can lead to health problems, and it is necessary to identify methods to counter this angiogenic effect of ROX. The VEGF/VEGFR2 signaling pathway is involved in the growth and reconstruction of new blood vessels during angiogenesis. In this study, a recombinant lentiviral vector encoding Vegfr2 shRNA was transfected into rat vascular endothelial cells and used in mouse matrigel plug and melanoma xenograft models to investigate its potential to regulate ROX-induced angiogenesis and tumor growth. Treating endothelial cells with ROX increased cell proliferation, migration, and a tube-like structure of growth relative to the control group. The addition of the lentiviral Vegfr2-silencing vector significantly attenuated the effects of ROX on endothelial cells. The hemoglobin content of mouse matrigel plugs treated with ROX was increased significantly. This effect was dramatically attenuated by the co-administration of shRNA targeting Vegfr2. The volume, weight and CD34 staining of the melanoma xenograft tumors increased by ROX were also attenuated by Vegfr2 silence. These results indicate that the down-regulation of VEGFR2 protein plays an inhibitory role in the ROX-promoted angiogenesis in vivo and in vitro. These data support the targeting of Vegfr2 gene as an effective means to treat ROX-induced angiogenesis and tumor growth.

Influence of dissolved organic matter on the anaerobic biotransformation of roxarsone accompanying microbial community response

Roxarsone (ROX), commonly employed as a livestock feed additive, largely remains unmetabolized and is subsequently excreted via feces. ROX could cause serious environmental risks due to its rapid transformation and high mobility in the anaerobic subsurface environment. Dissolved organic matter (DOM) is an important constituent of fecal organics in livestock waste and could affect the ROX biotransformation. Nonetheless, the underlying mechanisms governing the interaction between DOM and ROX biotransformation have not yet been elucidated in the anaerobic environment. In this study, the changes of ROX, metabolites, and microbial biomass in the solutions with varying DOM concentrations (0, 50, 100, 200, and 400 mg/L) under anaerobic environments were investigated during the ROX (200 mg/L) degradation. EEM-PARAFAC and metagenomic sequencing were combined to identify the dynamic shifts of DOM components and the functional microbial populations responsible for ROX degradation. Results indicated that DOM facilitated the anaerobic biotransformation of ROX and 200 mg/L ROX could be degraded completely in 28 h. The tryptophan-like within DOM functioned as a carbon source to promote the growth of microorganisms, thus accelerating the degradation of ROX. The mixed microflora involved in ROX anaerobic degrading contained genes associated with arsenic metabolism (arsR, arsC, acr3, arsA, nfnB, and arsB), and arsR, arsC, acr3 exhibited high microbial diversity. Variations in DOM concentrations significantly impacted the population dynamics of microorganisms involved in arsenic metabolism (Proteiniclasticum, Exiguobacterium, Clostridium, Proteiniphilum, Alkaliphilus, and Corynebacterium spp.), which in turn affected the transformation of ROX and its derivatives. This study reveals the mechanism of ROX degradation influenced by the varying concentrations of DOM under anaerobic environments, which is important for the prevention of arsenic contamination with elevated levels of organic matter.

Facet-dependent adsorption of aromatic organoarsenicals on hematite: The mechanism and environmental impact

Aromatic organoarsenic feed additives have been extensively used in poultry and livestock farming; however, a risk of releasing toxic inorganic arsenic exists when they are exposed to the environment. An in-depth understanding of the adsorption -migration behavior of aromatic organoarsenicals on environmental media is limited. In this study, p-arsanilic acid (p-ASA) and roxarsone (ROX) were considered as examples to systematically study their adsorption behaviors on the surface of hematite, a representative iron oxide in soil. By comparing the adsorption abilities and adsorption kinetics of hematite exposed with different facets (hexagonal nanoplates, HNPs, mainly exposed with {001} facets and hexagonal nanocubes, HNCs, exposed with {012} facets), combined with in situ shell-isolated nanoparticle enhanced Raman spectroscopy characterization and density functional theory simulation, the facet-dependent adsorption performance was observed and the mechanism revealed. The results showed that p-ASA formed a bidentate binuclear complex on HNCs and HNPs, whereas ROX formed monodentate mononuclear and bidentate binuclear configurations on the {001} and {012} facets, respectively. These differences not only lead to facet-dependent adsorption capacities but also affect their stability, as verified by sequential extraction experiments, affecting the environmental behavior and fate of aromatic organoarsenicals. This study not only provides insights into the environmental behavior of aromatic organoarsenicals but also offers theoretical support for the development of functional adsorbents and remediation strategies.

Cysteamine hydrochloride affects ocular development and triggers associated inflammation in zebrafish

The increasing use of cosmetics has raised widespread concerns regarding their ingredients. Cysteamine hydrochloride (CSH) is a newly identified allergenic component in cosmetics, and therefore its potential toxicity needs further elucidation. Here, we investigated the in vivo toxicity of CSH during ocular development utilizing a zebrafish model. CSH exposure was linked to smaller eyes, increased vasculature of the fundus and decreased vessel diameter in zebrafish larvae. Moreover, CSH exposure accelerated the process of vascular sprouting and enhanced the proliferation of ocular vascular endothelial cells. Diminished behavior in response to visual stimuli and ocular structural damage in zebrafish larvae after CSH treatment were confirmed by analysis of the photo-visual motor response and pathological examination, respectively. Through transcriptional assays, transgenic fluorescence photography and molecular docking analysis, we determined that CSH inhibited Notch receptor transcription, leading to an aberrant proliferation of ocular vascular endothelial cells mediated by Vegf signaling activation. This process disrupted ocular homeostasis, and induced an inflammatory response with neutrophil accumulation, in addition to the generation of high levels of reactive oxygen species, which in turn promoted the occurrence of apoptotic cells in the eye and ultimately impaired ocular structure and visual function during zebrafish development.

Toxic effects of long-term dual or single exposure to oxytetracycline and arsenic on Xenopus tropicalis living in duck wastewater

Direct discharge of aquaculture wastewater may have toxic effects, due to the presence of heavy metals, antibiotics, and even resistant pathogens, but little attention has been given. Here, tanks simulating a wild ecosystem were built to study the effects of long-term exposure to duck wastewater containing oxytetracycline (OTC) and/or arsenic (As) on the growth, physiological function, and gut microbiota evolution of Xenopus tropicalis. The results showed that duck wastewater had no apparent impact on X. tropicalis, but the impact increased significantly (P < 0.05) with exposure to OTC and/or As, especially the impact on body weight and growth rate. Biochemical indicators revealed varying degrees of oxidative stress damage, hepatotoxicity (inflammation, necrosis, and sinusoids), and collagen fibrosis of X. tropicalis in all treated groups after 72 days of exposure, which indirectly inhibited X. tropicalis growth. Moreover, 16S rDNA amplicon sequencing results showed that the gut microbiota structure and metabolic function were perturbed after chronic exposure, which might be the leading cause of growth inhibition. Interestingly, the abundance of intestinal resistance genes (RGs) increased with exposure time owing to the combined direct and indirect effects of stress factors in duck wastewater. Moreover, once the RGs were expressed, the resistance persisted for at least 24 days, especially that conferred by tetA. These results provide evidence of the toxic effects of DW containing OTC (0.1-4.0 mg/L) and/or As (0.3-3.5 µg/L) on amphibians and indicate that it is vital to limit the usage of heavy metals and antibiotics on farms to control the biotoxicity of wastewater.

Effects of dissolved organic matter derived from chicken manure on the biotransformation of roxarsone in soil

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX), widely used as a livestock feed additive, is excreted untransformed in large concentrations. Accumulation of this manure in the open environment increases dissolved organic matter (DOM) and ROX in soil within the aeration zone. And microbial action plays a dominant role in the transformation of ROX. However, the specific effect of DOM on the biotransformation of ROX is not known. In this paper, we investigated the transformation rate, metabolite content, and microbial community response of ROX in soils with different DOM concentrations (71.61, 100, 200, 500, and 800 mg L-1). The transformation of ROX was consistent with first-order transformation kinetics. DOM promoted the transformation of ROX, and with high DOM (DOM ≥200 mg L-1), ROX was transformed almost completely within two days. In this case, DOM provided nutrients to microorganisms and promoted their growth, accelerating the transformation of ROX. Also, the solubility of ROX was enhanced by DOM to increase its bioavailability. The microbial diversity was negatively correlated with DOM concentration and ROX transformation time; during the transformation of ROX, Bacillus, Arthrobacter, Enterococcus, Acinetobacter, and Pseudomonas became dominant in the soil with anomalously high levels of DOM. This study demonstrates the transformation process of ROX under actual environmental conditions where organic matter coexists with ROX, and this understanding is important for the prevention and control of arsenic pollution in soil within the aeration zone with anomalously high levels of DOM.

A Review on Electrospinning as Versatile Supports for Diverse Nanofibers and Their Applications in Environmental Sensing

Rapid industrialization is accompanied by the deterioration of the natural environment. The deepening crisis associated with the ecological environment has garnered widespread attention toward strengthening environmental monitoring and protection. Environmental sensors are one of the key technologies for environmental monitoring, ultimately enabling environmental protection. In recent decades, micro/nanomaterials have been widely studied and applied in environmental sensing owing to their unique dimensional properties. Electrospinning has been developed and adopted as a facile, quick, and effective technology to produce continuous micro- and nanofiber materials. The technology has advanced rapidly and become one of the hotspots in the field of nanomaterials research. Environmental sensors made from electrospun nanofibers possess many advantages, such as having a porous structure and high specific surface area, which effectively improve their performance in environmental sensing. Furthermore, by introducing functional nanomaterials (carbon nanotubes, metal oxides, conjugated polymers, etc.) into electrospun fibers, synergistic effects between different materials can be utilized to improve the catalytic activity and sensitivity of the sensors. In this review, we aimed to outline the progress of research over the past decade on electrospinning nanofibers with different morphologies and functional characteristics in environmental sensors.

The VEGFR2/mTOR/S6K1 pathway involved in the angiogenic effects of roxarsone in vitro and in vivo

Roxarsone, an organoarsenic compound used in poultry industry to increase weight gain, is widely used as a feed additive in some developing countries. Roxarsone has a low absorption rate and is mostly excreted with feces, which could pose a risk to human health through environmental and animal food routes. Roxarsone has been demonstrated to have tumor-promoting and proangiogenic effects. Herein, we report the role of VEGFR2/mTOR/S6K1 signaling in roxarsone-promoted vessel endothelial cell growth and angiogenesis in the Matrigel plug model and the mouse B16 cell tumor transplantation model. In angiogenesis-related experiments in vitro, 1.0 μM roxarsone significantly increased the activity, proliferation, migration, and tube formation of rat vascular endothelial cells. In addition, 1.0 μM roxarsone upregulated the protein levels of mTOR, phosphorylated mTOR, S6K1, and phosphorylated S6K1 and significantly increase the expression of Mtor and S6k1 mRNA. Rapamycin and SU5416 significantly inhibited the effects of 1.0 μM roxarsone on cell growth. Furthermore, the weight, volume, and CD31 expression of B16-F10 xenografts and Matrigel plugs in mice were upregulated by 25 mg/kg roxarsone. The protein and mRNA levels of mTOR, S6K1 and its phosphorylated protein were significantly increased in the roxarsone treatment group in xenografts. SU5416 and a short hairpin RNA targeting Vegfr2 significantly reduced roxarsone-promoted xenograft and Matrigel plug growth. In summary, this study indicated that the VEGFR2/mTOR/S6K1 signaling plays a regulatory role in roxarsone-mediated promotion angiogenesis and enhanced tumor growth.

Environmental Behavior and Remediation Methods of Roxarsone

Roxarsone (ROX) is used extensively in the broiler chicken industry, and most is excreted in poultry litter. ROX degradation produces inorganic arsenic, which causes arsenic contamination of soil and aquatic environment. Furthermore, elevated arsenic concentrations are found in livers of chickens fed ROX. Microorganisms, light, and ions are the main factors that promote ROX degradation in the environment. The adsorption of ROX on different substances and its influencing factors have also been studied extensively. Additionally, the remediation method, combining adsorption and degradation, can effectively restore ROX contamination. Based on this, the review reports the ecological hazards, discussed the transformation and adsorption of ROX in environmental systems, documents the biological response to ROX, and summarizes the remediation methods of ROX contamination. Most previous studies of ROX have been focused on identifying the mechanisms involved under theoretical conditions, but more attention should be paid to the behavior of ROX under real environmental conditions, including the fate and transport of ROX in the real environment. ROX remediation methods at real contaminated sites should also be assessed and verified. The summary of previous studies on the environmental behavior and remediation methods of ROX is helpful for further research in the future.

Evaluation of Dittrichia viscosa Aquaporin Nip1.1 Gene as Marker for Arsenic-Tolerant Plant Selection

Dittrichia viscosa (L.) Greuter is gaining attention for its high genetic plasticity and ability to adapt to adverse environmental conditions, including heavy metal and metalloid pollution. Uptake and translocation of cadmium, copper, iron, nickel, lead, and zinc to the shoots have been characterized, but its performance with arsenic is less known and sometimes contradictory. Tolerance to As is not related to a reduced uptake, but the null mutation of the aquaporin Nip1.1 gene in Arabidopsis makes the plant completely resistant to the metalloid. This aquaporin, localized in the endoplasmic reticulum, is responsible for arsenite and antimony (Sb) membrane permeation, but the uptake of arsenite occurs also in the null mutant, suggesting a more sophisticated action mechanism than direct uptake. In this study, the DvNip1 gene homologue is cloned and its expression profile in roots and shoots is characterized in different arsenic stress conditions. The use of clonal lines allowed to evidence that DvNip1.1 expression level is influenced by arsenic stress. The proportion of gene expression in roots and shoots can be used to generate an index that appears to be a promising putative selection marker to predict arsenic-resistant lines of Dittrichia viscosa plants.

Phenylarsonics in concentrated animal feeding operations: Fate, associated risk, and treatment approaches

Phenylarsonics are present as additives in animal feed in some countries. As only a small fraction of these additives is metabolized in animals, they mostly end up in the environment. A comprehensive investigation of the fate of these additives is crucial for evaluating their risks. This review aims to provide a clear understanding of the transformation mechanism of phenylarsonics in vivo and in vitro and to evaluate their fate and associated risks. Degradation of phenylarsonics releases toxic As species (mainly as inorganic arsenic (iAs)). Trivalent phenylarsonics are the metabolites or biotic degradation intermediates of phenylarsonics. The cleavage of As groups from trivalent phenylarsonics catalyzed by C-As lyase or other unknown pathways generates arsenite (As(III)). As(III) can be further oxidized to arsenate (As(V)) and methylated to methyl-arsenic species. The half-lives associated with abiotic degradation of phenylarsonics ranged from a few minutes to tens of hours, while those associated with biotic degradation ranged from several days to hundreds of days. Abiotic degradation resulted in a higher yield of iAs than biotic degradation. The use of phenylarsonics led to elevated total As and iAs levels in animal products and environmental matrices, resulting in As exposure risk to humans. The oxidation of phenylarsonics to As(V) facilitated the sorptive removal of As, which provides a general approach for treating these compounds. This review provides solid evidence that the use of phenylarsonics has adverse effects on both human health and environmental safety, and therefore, supports their withdrawal from the global market.

Arsenic in soils contaminated by arsenic-containing chemical weapons in a site of Jilin, China: fraction and bioaccessibility

At the end of World War II, the Japanese abandoned arsenic (As)-containing chemical weapons (CWs) in China. During the long-term burial process, the As-containing agents leaked into the environment due to the corrosion of weapon shells. This study explored the surface distribution, fraction composition, and bioaccessibility of As in the soil contaminated by chemical weapons in a site of Jilin Province, China. Results showed that As was enriched in the soil of CWs buried and the maximum concentration of As in this area was 110 mg/kg (dry weight). In terms of fraction, As primarily accumulated in amorphous Fe/Al-oxides bound and residual fractions. Moreover, from the perspective of fractions with potential environmental risks, As accounted for 45.6-82.0% and 61.0-80.7% of the fractions extracted by Wenzel and Shiowatana sequential extraction procedure (SEP), respectively. Bioaccessibility can also be used to assess environmental risks. The mean values of As bioaccessibility were as follows: gastric phase (15.0%) > colon phase (14.8%) > small intestinal phase (13.3%), and the As bioaccessibility was closely related to the Fe/Al oxide bound fraction. Compared with the surrounding farmland, the potential environmental risk of soil pollution was more significant in the CW burial areas. This study provided support for remediation of As-containing agent-contaminated soil in China.

Transient behavior of arsenic in vadose zone under alternating wet and dry conditions: A comparative soil column study

The water and oxygen contents of the vadose zone change cyclically depending upon the meteorological condition (e.g., intermittent rainfall), which can affect the biogeochemical reactions that govern the fate of arsenic (As). To simulate and evaluate the transient behavior of As in this zone when subjected to repeated wet and dry conditions, soil column experiments with different soil properties were conducted. Three wetting-drying cycles resulted in the fluctuation of water and dissolved oxygen contents, and consequently, the reduction-oxidation potential in the soil columns. Under these circumstances, the biotic reduction of As(V) to As(III) was observed, especially in the column filled with soils enriched in organic matter. Most of the As was found to be associated with soil particles rather than to be dissolved in the pore water in all of the columns tested. Retention of As was more preferable in the soil column with a higher Fe content and bulk density, which provided more sorption sites and reaction time, respectively. However, a considerable amount of soil-bound As could be remobilized and released back to the pore water with the repetition of wetting and drying due to the transformation of As(V) to As(III).

Energy balance assessment on chicken manure for biogas production in Rabat-Salé-Zemmour-Zaïr of Morocco

Chicken manure management has grabbed significant attention in Morocco due to the increasing demand on chicken and eggs. Bioconversion of chicken manure to biogas could reduce the chicken manure amount as well as generate clean energy. To evaluate the feasibility of converting chicken manure to biogas in terms of energy gain, the energy balance of the chicken manure for biogas production in the region of Rabat-Salé-Zemmour-Zaïr of Morocco has been investigated. The result showed that there was an energy gain of 1350 MJ for per tonne of dry chicken manure was converted to biogas. The energy gain increased to 3996 MJ/tonne of dry chicken manure when the wheat straw was added to co-digest with chicken manure. With consideration of converting the obtained biogas for electricity generation, there was extra electricity for sale after subtracting the electricity consumed inside the poultry industry. Comparing with co-firing, pyrolysis, and gasification, chicken manure anaerobic digestion was superior in terms of energy gain.