Public Health Risk of Arsenic Species in Chicken Tissues from Live Poultry Markets of Guangdong Province, China

Navigating Antimicrobials and Combating Antimicrobial Resistance: Challenges, Impacts, and Strategies for Global Action

Antimicrobial resistance (AMR) is one of the biggest problems facing the scientific and medical communities. According to WHO, this growing issue might make once-effective antibiotics obsolete and pose a substantial risk to public health. Estimates indicate that multimillion deaths were either directly or indirectly caused by AMR, making it one of the most substantial risks to public health and development in the world. The issue of AMR is primarily caused by healthcare workers' excessive and inappropriate use of antimicrobial agents. Dentists are believed to prescribe a considerable portion of all antibiotics globally. The emergence of AMR, its causes, and its effects on human health are examined in this article, with special attention to dental offices and medical facilities. It draws attention to the rising issue of antibiotic overprescription and abuse, particularly in low- and middle-income countries, where improper antibiotic use is an everyday practice around the globe. The article discusses the role of antimicrobial stewardship programs and the importance of implementing precise, evidence-based practices in preventing AMR. Since antibiotic abuse in livestock greatly accelerates the spread of resistance, the role of antibiotics in animal agriculture is also investigated. To address AMR, the paper highlights the necessity of a global, coordinated response that bolsters surveillance systems, cuts back on needless antibiotic use, and expands access to alternative treatments. Recent research has called into question the efficacy of preventive antibiotic medication in these situations. According to other researchers, it might not help avoid surgical site infections. However, other experts say disrupting deeper tissues and local mucosal defenses during an intraoral surgical operation may raise the risk of infection even when antibiotics are used.

Improper toy waste handling can harm human health via seafood consumption: A comprehensive health risk assessment of heavy metals

Toy production has been increasing over the last few decades to meet the growing demands for toys across the globe, which has inevitably worsened the problem of toy waste. Given the lack of modern waste disposal facilities, rural villagers in many developing countries often discard and incinerate toy waste in backyards or riverbanks, which may release the pollutants from toys (e.g., heavy metals), contaminate the surrounding areas, and eventually threaten the health of residents. As such, this study examined the impact of improper toy waste handling on the nearby aquaculture site by measuring the contamination level of heavy metals (As, Cd, Cu, Pb, and Zn) in the sediment and seafood (crabs, shrimps, and fish). The health risk of heavy metals via seafood consumption was assessed in different groups of people (males, females, teenagers, and seniors). Results showed that the sediment and seafood at the aquaculture site were generally not contaminated with heavy metals (contamination factor and bioaccumulation factor <1). However, consuming the seafood cultured at this site, especially for crabs, could pose a health risk to humans due to As and Cd (hazard quotient > 1), irrespective of their age and gender. This risk could not be lowered by cooking, except As by boiling. Overall, we revealed that improper toy waste handling did not cause severe heavy metal pollution in the surrounding environment, but the consumption of contaminated seafood could still threaten human health. To safeguard public health, we propose that toy waste should be appropriately treated by the authorities concerned. In addition, consuming seafood with long culture periods (e.g., crabs) should be reduced to minimize the dietary intake of heavy metals and their associated health risk.

Toxic Metals and Metalloids in Food: Current Status, Health Risks, and Mitigation Strategies

PURPOSE OF REVIEW

Exposure to toxic metals/metalloids, such as arsenic (As), cadmium (Cd), and lead (Pb), through food consumption is a global public health concern. This review examines the contamination status of these metals/metalloids in food, assesses dietary intake across different populations, and proposes strategies to reduce metal/metalloid exposures throughout the food chain.

RECENT FINDINGS

For the general population, dietary intake of metals/metalloids is generally lower than health-based guidance values. However, for vulnerable populations, such as infants, children, and pregnant women, their dietary intake levels are close to or even higher than the guidance values. Among different food categories, seafood shows higher total As, but largely present as organic species. Rice accumulates higher As concentration than other cereals, with inorganic As (iAs) and dimethylarsinic acid (DMA) being the main As species. Methylated thioarsenate species, such as dimethylmonothioarsenate, have also been detected in rice. The distribution of iAs and DMA in rice shows geographical variation. Additionally, seafood and cocoa products generally contain more Cd than other food, but seafood consumption does not significantly increase in adverse health effects due to its high zinc and iron content. Compared to As and Cd, Pb concentrations in food are generally lower. To minimize the health risks of metal/metalloid exposure, several strategies are proposed. Food contamination with toxic metals/metalloids poses significant concerns for human health, particularly for vulnerable populations. This review provides scientific evidence and suggestions for policy makers to reduce human exposure of metals/metalloids via dietary intake.

Transformation of p-arsanilic acid by dissolved Mn(III) and enhanced arsenic removal: Mechanism, toxicity and performance in complicated water matrices

Dissolved Mn(III), as a potent one-electron transfer oxidant, is ubiquitous in natural waters and sediments and actively involved in the transformation of organics in biogeochemical processes and water treatment. However, the important role of Mn(III) has long been overlooked because of its short life. This study was the first to investigate the performance of Mn(III) in organoarsenic transformation and to highlight the environmental implications. Both homogeneous and heterogeneous Mn(III)-based systems were effective to remove p-arsanilic acid (p-ASA, 15 μM) with degradation efficiency approaching 40.4 %-98.3 %. Two degradation pathways of p-ASA were proposed, in which As-C bond and amino group were vulnerable sites to Mn(III) attack, leading to the formation of more toxic arsenate (As(V)) and nitarsone. Through transforming organoarsenic to inorganic arsenic species, the removal efficiency of total arsenic and dissolved organics were enhanced to 65.1 %-95.5 % and 16.6 %-36.6 %, respectively, by post-treatment of coagulation or adsorption, accompanied with significant reduction of cytotoxicity and environmental risks. Particularly, polymeric ferric sulfate and granular activated alumina showed superior performance in the total As removal. Moreover, oxidation efficiency of Mn(III) was hardly affected by common cations and anions (e.g., Ca2+, Mg2+, NH4+, NO3-, SO4-), halide ions (e.g., Cl-, Br-) and natural organic matter, showing high robustness for organoarsenic removal under complicated water matrices. Overall, this study shed light on the significance of Mn(III) to the fate of organoarsenics in manganese-rich environments, and demonstrated the promising potential of Mn(III)-based strategies to achieve targeted decontamination in water/wastewater purification.

Microplastics and arsenic speciation in edible bivalves from the coast of China: Distribution, bioavailability, and human health risk

Bivalves, such as oysters and mussels, are exposed to environmental pollutants, like microplastics (MPs) and arsenic (As). This study investigated co-existence and interaction of MPs and As (total As and As species) in two bivalve species from the Chinese coastline. Smaller MPs (20-100 μm) averaged 30.98 items/g, while larger MPs (100-500 μm) averaged 2.98 items/g. Oysters contained more MPs (57.97 items/g) in comparison to mussels (11.10 items/g). In Contrast, mussels had a higher As concentrations (8.36-23.65 mg/kg) than oysters (4.97-11.02 mg/kg). The size and composition of MPs influenced As uptake and speciation in bivalves, with inorganic arsenic (iAs) and methylated arsenic (MMA and DMA) correlating with larger-sized MPs. Polyethylene (PE) may interact with the formation of arsenobetaine (AsB) in oyster. This study provides valuable insights into the interaction of MPs and As in marine ecosystems and highlights their implications for food safety.

Prevalence and genomic-based antimicrobial resistance analysis of Avibacterium paragallinarum isolates in Guangdong Province, China

Infectious coryza (IC) is an acute infectious respiratory disease in chickens that is caused by Avibacterium paragallinarum (A. paragallinarum). A. paragallinarum poses a significant threat to poultry health due to its virulence and multidrug resistance. This study isolated and identified 21 A. paragallinarum isolates from Guangdong between 2022 and 2023. Biochemical tests showed that 100% of A. paragallinarum isolates fermented glucose but did not ferment alginate and galactose, and only YZ18 was nicotinamide adenine dinucleotide independent. To determine the genetic relatedness between these isolates and NCBI reference strains, whole-genome-based phylogenetic analysis was employed. In addition, analysis of the 2,000 bp-length hmtp210 gene showed that the hmtp210 gene was strongly associated with A. paragallinarum serotypes. Meanwhile, a PCR assay for serotyping A. paragallinarum was developed based on the hmtp210 gene, this assay has high sensitivity and specificity. The antimicrobial susceptibility of isolates was assessed using the disk diffusion method. The antibiotic resistance genes of isolates were analyzed using the genomic method. Phenotypic resistance to ampicillin (95.2%), streptomycin (95.2%), methotrexate-sulfamethoxazole (90.5%), and tetracycline (85.7%) was most frequent among the isolates. All of the isolates exhibited resistance to multiple drugs, and furthermore, the isolates possessed a collective total of 14 genes associated with antibiotic resistance. This study will contribute to advancing our knowledge of A. paragallinarum antibiotic resistance and provide a scientific basis for the prophylaxis and treatment of IC, and the subsequent rational design of potential clinical therapeutics.

Comparative study of Fe(II)/sulfite, Fe(II)/PDS and Fe(II)/PMS for p-arsanilic acid treatment: Efficient organic arsenic degradation and contrasting total arsenic removal

As a widely used feed additives, p-arsanilic acid (p-AsA) frequently detected in the environment poses serious threats to aquatic ecology and water security due to its potential in releasing more toxic inorganic arsenic. In this work, the efficiency of Fe(II)/sulfite, Fe(II)/PDS and Fe(II)/PMS systems in p-AsA degradation and simultaneous arsenic removal was comparatively investigated for the first time. Efficient p-AsA abatement was achieved in theses Fe-based systems, while notable discrepancy in total arsenic removal was observed under identical acidic condition. By using chemical probing method, quenching experiments, isotopically labeled water experiments, p-AsA degradation was ascribed to the combined contribution of high-valent Fe(IV) and SO4•-in these Fe(II)-based system. In particular, the relative contribution of Fe(IV) and SO4•- in the Fe(II)/sulfite system was highly dependent on the molar ratio of [Fe(II)] and [sulfite]. Negligible arsenic removal was observed in the Fe(II)/sulfite and Fe(II)/PDS systems, while ∼80% arsenic was removed in the Fe(II)/PMS system under identical acidic condition. This interesting phenomenon was due to that ferric precipitation only occurred in the Fe(II)/PMS system. As(V) was further removed via adsorption onto the iron precipitate or the formation of ferric arsenate-sulfate compounds, which was confirmed by particle diameter measurements, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Through tuning solution pH, complete removal of total arsenic could achieve in all three systems. Among these three Fe-based technologies, the hybrid oxidation-coagulation Fe(II)/PMS system demonstrated potential superiority for arsenic immobilization by not requiring pH adjustment for coagulation and facilitating the in-situ generation of ferric arsenate-sulfate compounds with comparably low solubility levels like scorodite. These findings would deepen the understanding of these three Fe-based Fenton-like technologies for decontamination in water treatment.

Assessing the health risks of coal-burning arsenic-induced skin damage: A 22-year follow-up study in Guizhou, China

Risk assessment of arsenic-induced skin damage has always received significant global attention. Theories derived from arsenic exposure in drinking water may not be applicable to the coal-burning type to arsenic-exposed area. Furthermore, very few studies have successfully determined the reference value of cumulative arsenic (CA) exposure that leads to specific skin lesions. In this study, we conducted a 22-year follow-up investigation to assess the risk of skin lesions and cancer resulting from long-term, multi-channel arsenic exposure from hazard identification, dose-response assessment, exposure assessment, and risk characterization. The results show that the arsenic exposure can significantly increase the prevalence of skin lesions. For each interquartile range increase of hair arsenic (HA) and CA, the risk of skin damage increased by 1.91 and 3.90 times, respectively. The lower confidence limit of the benchmark dose of HA of arsenic-induced various skin lesions ranged from 0.07 to 0.12 μg·g-1, and 932.57 to 1368.92 mg for CA. The chronic daily intake, lifetime average daily dose in the arsenic-exposed area after the comprehensive prevention and control measures have decreased significantly, but remained higher than the daily baseline level of 3.0 μg·kg-1·d-1. Even as recently as 2020, the hazard quotients and hazard index still exceeded 1, measuring 155.33 and 55.20, and the lifetime excess risk of skin cancer (2.80 × 10-3) remains significantly higher than the acceptable level of 10-6. Our study underscores the effectiveness of comprehensive prevention and control measures in managing high arsenic exposure in coal-burning arsenic poisoning areas. However, it is crucial to acknowledge that the risk of both non-carcinogenic and carcinogenic effects on the skin remains substantially higher than the acceptable level. We recommend setting reference limits for monitoring skin damage among individuals exposed to arsenic, with a recommended upper limit of 0.07 μg·g-1 for HA and a maximum acceptable level of 935.57 mg for CA.

Characterization of atmospheric mercury from mercury-added product manufacturing using passive air samplers

Although alternatives to mercury (Hg) are available in most products and industrial activities, Hg continues to be an ingredient in some products, including fluorescent lamps and electrical and electronic equipment (EEE). In this work, low-cost passive air samplers (PASs) were used to investigate the atmospheric Hg pollution in Zhongshan, a large industrial city and major hub of mercury-added product manufacturing in South China. The GEM concentrations in the atmosphere were measured for two weeks during the summer of 2019 at a total of 144 sites across Zhongshan. Comparison with the results of active sampling confirmed that the PASs yielded accurate and reliable gaseous elemental mercury (GEM) concentrations and were thus well-suited for multi-site field monitoring. The mean GEM concentrations in the areas with mercury-added product manufacturing activities (5.1 ± 0.4 ng m-3) were significantly higher than those in other parts of Zhongshan (1.5 ± 0.4 ng m-3), indicating that local releases, rather than regional transport, were responsible for the atmospheric Hg pollution. Elevated GEM concentrations (up to 11.4 ng m-3) were found in the vicinity of fluorescent lamp and EEE factories and workshops, indicating significant Hg vapor emissions, presumably from the outdated production technologies and non-standard operation by under-trained workers. The Hg emissions from mercury-added product manufacturing were estimated to be 0.06 and 7.8 t yr-1 for Zhongshan and China, respectively, based on the scales of fluorescent lamp and EEE production. The non-carcinogenic health risk of Zhongshan residents from inhalation and ingestion was judged acceptable, whereby the inhalation exposure in Hg-polluted areas exceeded that of dietary ingestion. These findings demonstrate that mercury-added product manufacturing still contributes notably to anthropogenic gaseous Hg releases in the industrial areas with intense mercury-added product manufacturing activities.

3D-Printed MOFs/Polymer Composite as a Separatable Adsorbent for the Removal of Phenylarsenic Acid in the Aqueous Solution

Metal-organic frameworks (MOFs) are emerging as advanced nanoporous materials to remove phenylarsenic acid, p-arsanilic acid (p-ASA), and roxarsone (ROX) in the aqueous solution, while MOFs are often present as powder state and encounter difficulties in recovery after adsorption, which greatly limit their practical application in the aqueous environments. Herein, MIL-101 (Fe), a typical MOF, was mixed with sodium alginate and gelatin to prepare MIL-101@CAGE by three-dimensional (3D) printing technology, which was then used as a separatable adsorbent to remove phenylarsenic acid in the aqueous solution. The structure of 3D-printed MIL-101@CAGE was first characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and thermogravimetry and differential thermogravimetry (TG-DTG). The octahedral morphology of MIL-101 (Fe) was found unchanged during the 3D printing process. Then, the adsorption process of MIL-101@CAGE on phenylarsenic acids was systematically investigated by adsorption kinetics, adsorption isotherms, adsorption thermodynamics, condition experiments, and cyclic regeneration experiments. Finally, the adsorption mechanism between MIL-101@CAGE and phenylarsenic acid was further investigated. The results showed that the Langmuir, Freundlich, and Temkin isotherms were well fit, and according to the Langmuir fitting results, the maximum adsorption amounts of MIL-101@CAGE on p-ASA and ROX at 25 °C were 106.98 and 120.28 mg/g, respectively. The removal of p-ASA and ROX by MIL-101@CAGE remained stable over a wide pH range and in the presence of various coexisting ions. The regeneration experiments showed that the 3D-printed MIL-101@CAGE could still maintain a more than 90% removal rate after five cycles. The adsorption mechanism of this system might include π-π stacking interactions between the benzene ring on the phenylarsenic acids and the organic ligands in MIL-101@CAGE, hydrogen-bonding, and ligand-bonding interactions (Fe-O-As). This study provides a new idea for the scale preparation of a separatable and recyclable adsorbent based on MOF material for the efficient removal of phenylarsenic acid in the aqueous solution.

Current advances in the detection and removal of organic arsenic by metal-organic frameworks

Arsenic (As) is a highly toxic heavy metal and has been widely concerned for its hazardous environmental impact. Aromatic organic arsenic (AOCs) has been frequently used as an animal supplement to enhance feed utilization and prevent dysentery. The majority of organic arsenic could be discharged from the body and evolve as highly toxic inorganic arsenic that is hazardous to the environment and human health via biological conversion, photodegradation, and photo-oxidation. Current environmental issues necessitate the development and application of multifunctional porous materials in environmental remediation. Compared to the conventional adsorbent, such as activated carbon and zeolite, metal-organic frameworks (MOFs) exhibit a number of advantages, including simple synthesis, wide variety, simple modulation of pore size, large specific surface area, excellent chemical stability, and easy modification. In recent years, numerous scientists have investigated MOFs related materials involved with organic arsenic. These studies can be divided into three categories: detection of organic arsenic by MOFs, adsorption to remove organic arsenic by MOFs, and catalytic removal of organic arsenic by MOFs. Here, we conduct a critical analysis of current research findings and knowledge pertaining to the structural characteristics, application methods, removal properties, interaction mechanisms, and spectral analysis of MOFs. We summarized the application of MOFs in organic arsenic detection, adsorption, and catalytic degradation. Other arsenic removal technologies and conventional substances are also being investigated. This review will provide relevant scientific researchers with references.

Interaction between roxarsone, an organic arsenic compound, with humic substances in the soil simulating environmental conditions

In environmental systems, the soil is a principal route of contamination by various potentially toxic species. Roxarsone (RX) is an arsenic (V) organic compound used to treat parasitic diseases and as an additive for animal fattening. When the animal excretes RX, the residues may lead to environmental contamination. Due to their physicochemical properties, the soil's humic substances (HS) are important in species distribution in the environment and are involved in various specific interaction/adsorption processes. Since RX, an arsenic (V) compound, is considered an emerging contaminant, its interaction with HS was evaluated in simulated environmental conditions. The HS-RX interaction was analyzed by monitoring intrinsic HS fluorescence intensity variations caused by complexation with RX, forming non-fluorescent supramolecular complexes that yielded a binding constant Kb (on the order of 103). The HS-RX interaction occurred through static quenching due to complex formation in the ground state, which was confirmed by spectrophotometry. The process was spontaneous (ΔG < 0), and the predominant interaction forces were van der Waals and hydrogen bonding (ΔH < 0 and ΔS < 0), with an electrostatic component evidenced by the influence of ionic strength in the interaction process. Structural changes in the HS were verified by synchronized and 3D fluorescence, with higher variation in the region referring to the protein-like fraction. In addition, metal ions (except ions Cu(II)) favored HS-RX interaction. When interacting with HS, the RX epitope was suggested by 1H NMR, which indicated that the entire molecule interacts with the superstructure. An enzyme inhibition assay verified the ability to reduce the alkaline phosphatase activity of free and complexed RX (RX-HS). Finally, this work revealed the main parameters associated with HS and RX interaction in simulated environmental conditions, thus, providing data that may help our understanding of the dynamics of organic arsenic-influenced soils.

Influence of Humic Acids on the Removal of Arsenic and Antimony by Potassium Ferrate

Although the removal ability of potassium ferrate (K₂FeO₄) on aqueous heavy metals has been confirmed by many researchers, little information focuses on the difference between the individual and simultaneous treatment of elements from the same family of the periodic table. In this project, two heavy metals, arsenic (As) and antimony (Sb) were chosen as the target pollutants to investigate the removal ability of K₂FeO₄ and the influence of humic acid (HA) in simulated water and spiked lake water samples. The results showed that the removal efficiencies of both pollutants gradually increased along the Fe/As or Sb mass ratios. The maximum removal rate of As(III) reached 99.5% at a pH of 5.6 and a Fe/As mass ratio of 4.6 when the initial As(III) concentration was 0.5 mg/L; while the maximum was 99.61% for Sb(III) at a pH of 4.5 and Fe/Sb of 22.6 when the initial Sb(III) concentration was 0.5 mg/L. It was found that HA inhibited the removal of individual As or Sb slightly and the removal efficiency of Sb was significantly higher than that of As with or without the addition of K₂FeO₄. For the co-existence system of As and Sb, the removal of As was improved sharply after the addition of K₂FeO₄, higher than Sb; while the latter was slightly better than that of As without K₂FeO₄, probably due to the stronger complexing ability of HA and Sb. X-ray energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the precipitated products to reveal the potential removal mechanisms based on the experimental results.

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.

Arsenic species and their health risks in edible seaweeds collected along the Chinese coastline

Edible seaweeds with a relatively high total arsenic concentration have been a global concern. As the largest seaweed producer, China contributes about 60 % of the global seaweed production. The present study investigated 20 seaweed species collected from representative seaweed farming sites in the six provinces along the Chinese coastline, of which Saccharina japonica, Undaria pinnatifida, Neopyropia spp., Gracilaria spp., Sargassum fusiforme were listed as the most consumed seaweeds in Food and Agriculture Organization of the United Nations (FAO). The inorganic arsenic (iAs) concentration in most of the seaweeds was below maximum limits (0.3 mg iAs/kg) as seaweed additives for infant food in the National Food Safety Standard of Pollutants in China (GB2762-2017, 2017), except for the species Sargassum, in which the iAs concentration significantly exceeded the limit and ranged from 15.1 to 83.7 mg/kg. Arsenic speciation in 4 cultivated seaweeds grown in both temperate and subtropical zones is reported for the first time. No significant differences in total As and iAs concentration were identified, except slightly higher total As concentration were found in Saccharina japonica growing in the temperate zone. The estimated daily intake (EDI) of toxic iAs via seaweed consumption was generally below the EFSA CONTAM Panel benchmark dose lower confidence limit (0.3 μg/kg bw/day) except for all Sargassum species where the EDI was significantly higher than 0.3 μg/kg bw/day. Moreover, the first-ever reported data on As speciation indicated very high iAs concentrations in Sargassum hemiphyllum and Sargassum henslowianum. To minimize the food chain iAs exposure, reducing both human intake of Sargassum spp. and the used of Sargassum spp. for animal feed is highly recommended. CAPSULE: This study showed that edible seaweed Sargassum spp. consumption may pose a health risk related to inorganic arsenic (iAs) exposure. The risk of iAs exposure via seaweed consumption or livestock is a concern that needs to be monitored. The arsenic accumulation and speciation may be predominantly species-dependent rather than environmental-dependent.

Review on fate and bioavailability of heavy metals during anaerobic digestion and composting of animal manure

Anaerobic digestion and composting are attracting increasing attention due to the increased production of animal manure. It is essential to know about the fate and bioavailability of heavy metals (HMs) for further utilisation of animal manure. This review has systematically summarised the migration of HMs and the transformation of several typical HMs (Cu, Zn, Cd, As, and Pb) during anaerobic digestion and composting. The results showed that organic matter degradation increased the HMs content in biogas residue and compost (with the exception of As in compost). HMs migrated into biogas residue during anaerobic digestion through various mechanisms. Most of HMs in biogas residue and compost exceeded relevant standards. Then, anaerobic digestion increased the bioavailable fractions proportion in Zn and Cd, decreased the F4 proportion, and raised them more than moderate environmental risks. As (III) was the main species in the digester, which extremely increased As toxicity. The increase of F3 proportion in Cu and Pb was due to sulphide formation in biogas residue. Whereas, the high humus content in compost greatly increased the F3 proportion in Cu. The F1 proportion in Zn decreased, but the plant availability of Zn in compost did not reduce significantly. Cd and As mainly converted the bioavailable fractions into stable fractions during composting, but As (V) toxicity needs to be concerned. Moreover, additives are only suitable for animal manure treated with slightly HM contaminated. Therefore, it is necessary to combine more comprehensive methods to improve the manure treatment and make product utilisation safer.

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.

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.

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

Arsenic is frequently found in poultry waste, most of which is transformed from feed additive organoarsenicals, resulting in arsenic pollution of soils and water around poultry farms. The North China Plain, an important area for livestock breeding of China, was chosen to investigate the pollution characteristics and assess the health risk of arsenic around chicken farms. Among the 138 chicken farms sampled, almost no roxarsone, a common organoarsenical, was detected in chicken feeds, manure, and surface soils, while the detectable rate of other arsenic species was high. Because of long-term enrichment, the concentrations of arsenic species in manure were generally higher than that in feed. As(III) was the main inorganic arsenic species in the manure, where is reducing environment. In surface soils beneath the accumulated manure, As(V) was the predominant arsenic species with 100% detectable rate. The detectable rate and average concentrations at 0 cm were generally higher than those at 25 cm depth, indicating that arsenic accumulated in the surface soils. In addition, a typical conceptual diagram of arsenic was developed to clarify the pollution process from feed to soil. Through health risk assessment of inorganic arsenic, the carcinogenic risk (CR) and non-carcinogenic risk (non-CR) were both negligible. The city of Jiaozuo had the highest CR and non-CR, which was 11 times higher than that of the city with the lowest risks. This study presents a clear picture and evaluation of arsenic pollution on chicken farms, inspiring future studies assessing arsenic pollution after the ban of organoarsenicals.

Seven potential sources of arsenic pollution in Latin America and their environmental and health impacts

This review presents a holistic overview of the occurrence, mobilization, and pathways of arsenic (As) from predominantly geogenic sources into different near-surface environmental compartments, together with the respective reported or potential impacts on human health in Latin America. The main sources and pathways of As pollution in this region include: (i) volcanism and geothermalism: (a) volcanic rocks, fluids (e.g., gases) and ash, including large-scale transport of the latter through different mechanisms, (b) geothermal fluids and their exploitation; (ii) natural lixiviation and accelerated mobilization from (mostly sulfidic) metal ore deposits by mining and related activities; (iii) coal deposits and their exploitation; (iv) hydrocarbon reservoirs and co-produced water during exploitation; (v) solute and sediment transport through rivers to the sea; (vi) atmospheric As (dust and aerosol); and (vii) As exposure through geophagy and involuntary ingestion. The two most important and well-recognized sources and mechanisms for As release into the Latin American population's environments are: (i) volcanism and geothermalism, and (ii) strongly accelerated As release from geogenic sources by mining and related activities. Several new analyses from As-endemic areas of Latin America emphasize that As-related mortality and morbidity continue to rise even after decadal efforts towards lowering As exposure. Several public health regulatory institutions have classified As and its compounds as carcinogenic chemicals, as As uptake can affect several organ systems, viz. dermal, gastrointestinal, peptic, neurological, respiratory, reproductive, following exposure. Accordingly, ingesting large amounts of As can damage the stomach, kidneys, liver, heart, and nervous system; and, in severe cases, may cause death. Moreover, breathing air with high As levels can cause lung damage, shortness of breath, chest pain, and cough. Further, As compounds, being corrosive, can also cause skin lesions or damage eyes, and long-term exposure to As can lead to cancer development in several organs.

Interface-Promoted Direct Oxidation of p-Arsanilic Acid and Removal of Total Arsenic by the Coupling of Peroxymonosulfate and Mn-Fe-Mixed Oxide

As one of the extensively used feed additives in livestock and poultry breeding, p-arsanilic acid (p-ASA) has become an organoarsenic pollutant with great concern. For the efficient removal of p-ASA from water, the combination of chemical oxidation and adsorption is recognized as a promising process. Herein, hollow/porous Mn-Fe-mixed oxide (MnFeO) nanocubes were synthesized and used in coupling with peroxymonosulfate (PMS) to oxidize p-ASA and remove the total arsenic (As). Under acidic conditions, both p-ASA and total As could be completely removed in the PMS/MnFeO process and the overall performance was substantially better than that of the Mn/Fe monometallic system. More importantly, an interface-promoted direct oxidation mechanism was found in the p-ASA-involved PMS/MnFeO system. Rather than activate PMS to generate reactive oxygen species (i.e., SO₄^·-, ·OH, and ¹O₂), the MnFeO nanocubes first adsorbed p-ASA to form a ligand-oxide interface, which improved the oxidation of the adsorbed p-ASA by PMS and ultimately enhanced the removal of the total As. Such a direct oxidation process achieved selective oxidation of p-ASA and avoidance of severe interference from the commonly present constituents in real water samples. After facile elution with dilute alkali solution, the used MnFeO nanocubes exhibited superior recyclability in the repeated p-ASA removal experiments. Therefore, this work provides a promising approach for efficient abatement of phenylarsenical-caused water pollution based on the PMS/MnFeO oxidation process.

Organoarsenic feed additives in biological wastewater treatment processes: Removal, biotransformation, and associated impacts

Aromatic organoarsenicals are widely used in animal feeding operations and cause arsenic contamination on livestock wastewater and manure, thereby raising the risk of surface water pollution. Biological wastewater treatment processes are often used for livestock wastewater treatment. Organoarsenic removal and biotransformation under aerobic and anaerobic conditions, and the associated impacts have received extensive attention due to the potential threat to water security. The removal efficiency and biotransformation of organoarsenicals in biological treatment processes are reviewed. The underlying mechanisms are discussed in terms of functional microorganisms and genes. The impacts associated with organoarsenicals and their degradation products on microbial activity and performance of bioreactors are also documented. Based on the current research advancement, knowledge gaps and potential research in this field are discussed. Overall, this work delivers a comprehensive understanding on organoarsenic behaviors in biological wastewater treatment processes, and provides valuable information on the control of arsenic contamination from the degradation of organoarsenicals in biological wastewater treatment processes.

Efficient Degradation of Organoarsenic by UV/Chlorine Treatment: Kinetics, Mechanism, Enhanced Arsenic Removal, and Cytotoxicity

Roxarsone (ROX) has been widely used as an organoarsenic additive in animal feeding operations and poses a risk to the environment. Here, we first report the efficient degradation of ROX by UV/chlorine, where the kinetics, removal of total arsenic (As), and cytotoxicity were investigated. The kinetics study presented that reactive chlorine species (RCS) and HO^• were the dominant species to react with ROX. Furthermore, the degradation rate of ROX can reach the maximum value at pH 7.5 due to the formation of more RCS. The degradation of ROX was affected by the amount of chlorine, pH, and water matrix. Through product analysis and Gauss theoretical calculation, two possible ROX degradation pathways were proposed. The free radicals attacked the As-C bond of ROX and resulted in releasing arsenate (As(V)). It was the reason that for an enhancement of the removal of total As by ferrous appeared after UV/chlorine, and over 98% of the total As was removed. In addition, cytotoxicity studies indicated that the cytotoxicity significantly enhanced during the degradation of ROX by UV/chlorine. However, by combination of UV/chlorine and adsorption, cytotoxicity can be greatly eliminated, probably due to the removal of As(V) and chlorinated products. These results further demonstrated that UV/chlorine treatment could be an effective method for the control of the potential environmental risks posed by organoarsenic.

Atmospheric mercury pollution caused by fluorescent lamp manufacturing and the associated human health risk in a large industrial and commercial city

Although already eliminated in most industrial processes, mercury, as an essential ingredient in all energy-efficient lighting technologies, is still used in fluorescent lamp manufacturing. This study was conducted to investigate the atmospheric pollution caused by fluorescent lamp production and assess the associated public health risk in a large industrial and commercial city of south China, Zhongshan, which is a major production hub of lighting products. Concentrations of total gaseous mercury (TGM) in the atmosphere were measured over a total of 342 sites in the industrial, commercial, and residential areas. The average levels of TGM in the industrial, commercial, and residential areas prior to the landing of a typhoon were 12 ± 11, 3.6 ± 2.1, and 2.7 ± 1.3 ng⋅m^-3, respectively. TGM concentrations in the industrial areas exhibited significant diurnal variation, with levels in the working hours being much higher than those in the non-working hours, which indicates that the high atmospheric mercury concentrations were contributed by local emissions, instead of regional transport. Most fluorescent lamp manufacturing activities in the city were shut down during a typhoon event, which resulted in a significant reduction in the average TGM level (down to 1.6 ± 1.8 ng⋅m^-3) and rendered the difference in the average TGM levels in the industrial areas no longer significant between the working and non-working hours. Elevated TGM levels (up to 49 ng⋅m^-3) were found near clusters of small-scale fluorescent lamp workshops in both industrial and commercial areas, which is indicative of significant emissions of mercury vapor resulting from obsolete equipment and production technologies. No significant non-carcinogenic risk was found for the general residents in the sampling area over the study period, while the risk for the workers in the fluorescent lamp manufacturing facilities and workshops could be higher. These findings indicate that fluorescent lamp manufacturing in the developing countries is a major source of atmospheric mercury.

Organoarsenic conversion to As(III) in subcritical hydrothermal reaction of livestock manure

Liquid phase produced by the subcritical hydrothermal liquefaction (HTL) of livestock manure is extensively used in agronomic and environmental applications, but the potential risks caused by inherent pollutants (e.g., roxarsone, ROX) of the livestock manure have not been considered. This study shows that less toxic ROX is completely converted into highly toxic As(III) and As(V) in the HTL reaction with temperature more than 240 °C. Moreover, more than 81.5% of As is distributed in the liquid phase generated by the livestock manure HTL reaction. Notably, the hydrothermal products of livestock manure facilitate the conversion of As(V) to As(III). The resulting hydrochar and aldehydes act as electron donors for As(V) reduction, thus resulting in the formation of As(III). Furthermore, the dissociated As promotes the depolymerization and deoxygenation of the macromolecular compounds to produce more small oxygen-containing compounds such as aldehydes, further boosting the As(V) reduction to As(III). These results indicate that the liquid phase of the livestock manure has potential risks in applications as a fertilizer. Such findings have substantial implications in biomass utilization and redox reactions of envirotechnical and biogeochemical relevance.

Anaerobic biotransformation of roxarsone regulated by sulfate: Degradation, arsenic accumulation and volatilization

Roxarsone, an extensively used organoarsenical feed additive, is often pooled in livestock wastewater. Sulfate exists ubiquitously in livestock wastewater and is capable for arsenic remediation. However, little is known about impacts of sulfate on roxarsone biotransformation during anaerobic digestion of livestock wastewater. In this study, the biodegradation of 5.0 mg L^-1 roxarsone, and the accumulation and volatilization of the generated arsenical metabolites in a sulfate-spiked upflow anaerobic granular blanket reactor were investigated. Based on the analysis of degradation products, the nitro and arsenate groups of roxarsone were successively reduced to amino and arsenite groups before the C-As bond cleavage. Effluent arsenic concentration was ∼0.75 mg L^-1, of which 82.9-98.5% were organoarsenicals. The maximum arsenic volatilization rate reached 32.6 μg-As kg^-1-VS d^-1. Adding 5.0 mg L^-1 sulfate enabled 66.7% and 45.9% decrease in inorganic arsenic concentration and arsenic volatilization rate, respectively. Arsenic content in the anaerobic granular sludge (AGS) was accumulated to 1250 mg kg^-1 within 420 days. Based on the results of FESEM-EDS and XPS, sulfate addition induced arsenic precipitation in the AGS through the formation of orpiment. Arsenic in the effluent, biogas and AGS accounted for 52.9%, 0.01% and 47.1% of the influent arsenic when the reactor operated stably. The findings from this study suggest that sulfate has effectively regulatory effects on arsenic immobilization and volatilization during anaerobic digestion of organoarsenic-contaminated livestock wastewater.

Potential contaminants and hazards in alternative chicken bedding materials and proposed guidance levels: a review

Bedding material or litter is an important requirement of meat chicken production which can influence bird welfare, health, and food safety. A substantial increase in demand and cost of chicken bedding has stimulated interest in alternative bedding sources worldwide. However, risks arising from the use of alternative bedding materials for raising meat chickens are currently unknown. Organic chemicals, elemental, and biological contaminants, as well as physical and management hazards need to be managed in litter to protect the health of chickens and consequently that of human consumers. This requires access to information on the transfer of contaminants from litter to food to inform risk profiles and assessments to guide litter risk management. In this review, contaminants and hazards of known and potential concern in alternative bedding are described and compared with existing standards for feed. The contaminants considered in this review include organic chemical contaminants (e.g., pesticides), elemental contaminants (e.g., arsenic, cadmium, and lead), biological contaminants (phytotoxins, mycotoxins, and microorganisms), physical hazards, and management hazards. Reference is made to scientific literature for acceptable levels of the above contaminants in chicken feed that can be used for guidance by those involved in selecting and using bedding materials.

Simultaneous degradation of p-arsanilic acid and inorganic arsenic removal using M-rGO/PS Fenton-like system under neutral conditions

In this study, magnetic material based reduced graphene oxide (M-rGO) was prepared through co-precipitation and displayed high catalytic efficiency together with persulfate (PS) for simultaneous p-arsanilic acid (p-ASA) decomposition and arsenic removal. Linear sweep voltammetry and chronoamperometric measurements with M-rGO revealed that PS was effectively bound to M-rGO surface and probably formed charge transfer complex, in which M-rGO was pivotal in mediating facile electron transfer. The effects of pH, temperatures, anions, p-ASA concentration, PS, and M-rGO dosages on p-ASA decomposition were studied in the system. Excellent degradation of p-ASA was carried out at a wide range of pH values, which was unattainable by other Fenton-like processes. Under optimal conditions, M-rGO exhibited prominent removal of both p-ASA (98.8 %) and inorganic arsenic (89.8 %). M-rGO had reasonably excellent repeatability and stability, and 77.7 % p-ASA degraded in the third recovered catalyst. The advantages of environmental friendliness, short reaction time, and straightforward synthesis of M-rGO will facilitate the development of heterogeneous Fenton-like catalysts under neutral conditions.

Simultaneous removal of para-arsanilic acid and the released inorganic arsenic species by CuFe2O4 activated peroxymonosulfate process

para-arsanilic acid (p-ASA), as a major phenylarsonic feed additive, was used annually in many countries. Once it enters the water environment, p-ASA would be transformed into hypertoxic inorganic arsenic species, causing severe arsenic pollution. In this study, magnetic copper ferrite (CuFe₂O₄) was applied to activate peroxymonosulfate (PMS) for p-ASA removal and synchronous control of the released inorganic arsenic species. Results showed that CuFe₂O₄/PMS system presented favorable oxidation ability and close to 85% of 10 mg/L p-ASA was eliminated under the condition of simultaneous dosing 0.2 g/L CuFe₂O₄ and 1 mM PMS. The rapid decomposition of p-ASA resulted from homogeneous PMS oxidation and the attack of reactive oxygen species (i.e., SO₄^-, HO and O₂^-), which was involved the heterogeneous PMS activation through the cycles between Fe(II)/Fe(III) and Cu(II)/Cu(I). Meanwhile, the released inorganic arsenic species during p-ASA degradation were found to be controllable via the adsorption on CuFe₂O₄ surface and metal hydroxyl groups played the crucial role. CuFe₂O₄/PMS system exhibited the stable and efficient performance within the broad range of pH 3.0-11.0. The existence of common anions (Cl^-, NO₃^-, HCO₃^-, SO₄^2-) and humic acid presented the slight inhibition for p-ASA degradation. The reduction of initial p-ASA concentration favored the p-ASA removal. Besides, the catalyst retained a favorable reactivity and stability even after four successive cycles and almost no metal leaching was observed. The rational degradation pathway was mainly involved in the cleavage of AsC bond, oxidation of amino group, substitution and oxidation of hydroxyl group. The transformation of arsenic species could be divided into the release of inorganic arsenic species, the oxidation of As(III) into As(V) and the adsorption of As(V) by CuFe₂O₄.

Dietary exposure to arsenic and human health risks in western Tibet

The health effects of drinking water exposure to inorganic arsenic are well known but are less well defined for dietary exposure. The rising concerns of arsenic risks from diet motivated this study of arsenic concentrations in highland barley, vegetables, meat, and dairy products to evaluate arsenic exposure source and to assess health risks among rural residents of Ngari area, western Tibet. Total arsenic and arsenic speciation were measured by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography combined with ICP-MS (HPLC-ICP-MS) respectively. Average total arsenic concentrations of 0.18 ± 0.21 (n = 45, median: 0.07 mg·kg^-1), 0.40 ± 0.57 (n = 17, median: 0.15 mg·kg^-1), 0.21 ± 0.16 (n = 12, median: 0.17 mg·kg^-1), and 0.18 ± 0.08 (n = 11, median: 0.22 mg·kg^-1) were observed in highland barley, vegetables, meat, and dairy products, respectively. Inorganic arsenic was determined to be the main species of arsenic in highland barley, accounting for about 64.4 to 99.3% (average 83.3%) of total arsenic. Nearly half (44.4%) of the local residents had ingested >3.0 × 10^-4 mg·kg^-1·d^-1 daily dose of arsenic from highland barley alone, above the maximum oral reference dose recommended by the United States Environmental Protection Agency (USEPA). The inorganic arsenic daily intake from highland barley was 3.6 × 10^-4 mg·kg^-1·d^-1. Dietary exposure to inorganic arsenic alone increased the cancer risk probability to 5.4 in 10,000, assuming that the inorganic arsenic in highland barley has the same carcinogenic effects as that in water.

Prevalence of Arsenic in chicken feed and its contamination pattern in different parts of chicken flesh: a market basket study

Organoarsenic compounds are widely used in chicken feed for control of coccidial parasite, quick weight gain, and for imparting attractive color to the chicken flesh. A study was conducted to assess the level of arsenic in both chicken feed and flesh. Chicken feed was collected from 10 farm houses and total arsenic was estimated. The quantitative estimation suggests that the four levels of chicken feed contain different quantities of arsenic load. The results demonstrated that feed at stages III and IV levels contain 0.01 mg/g and 0.018 mg/g of arsenic respectively. However, at stages I and II levels, the feed contains 0.005 mg/g and 0.0052 mg/g of arsenic respectively. Proceeding similarly, chicken flesh was collected from ten vendors in the local markets of Burdwan. The experimental results revealed that deposition of arsenic in different parts of chicken body is not same. The highest accumulation was recorded in the flesh of chest followed by stomach, whereas flesh of the legs and heart showed lower levels of arsenic accumulation. A comprehensive calculation was thereafter done to assess the total amount of arsenic ingestion through consumption of chicken. If a person takes 60.0 g of chicken flesh (leg, breast, muscles, and stomach) everyday, then the person may consume 0.186-0.372 μg of arsenic per day. This study therefore clearly suggests that excessive consumption of poultry chicken may prove to be fatal. However, further research is necessary to confirm the present findings. To the best of our knowledge, this is probably the first report on the likelihood of arsenic contamination in the flesh of different body parts of poultry chicken from Eastern India.

Probabilistic human health risk assessment of arsenic under uncertainty in drinking water sources in Jiangsu Province, China

Concentrations of arsenic (As) in 65 drinking water sources in Jiangsu Province of China were analyzed from January 2013 to December 2015. The drinking water sources are classified into five water systems of the Yangze River, the Taihu Lake, the Huai River, the Yishusi River, and other lakes or reservoirs, which are termed as WS-A, WS-B, WS-C, WS-D, and WS-E, respectively. Health risk assessments associated with As in terms of total carcinogenic risk and total hazard index were performed for children (0-5 years), teenagers (6-17 years), and adults (≥ 18 years), respectively. Probabilistic risk assessments were obtained by applying Monte Carlo approach with consideration of uncertainty. The results indicated that in drinking water sources of WS-A, WS-C, and WS-D, maximum concentrations of As were 28 μg/L, 40 μg/L, and 17 μg/L, respectively, which were higher than 10 μg/L recommended by the World Health Organization occurred. Based on the samples investigated in this study, the mean health risks are the highest in drinking water source WS-D and lowest in WS-E for both male and female children, teenagers, and adults. For drinking water source WS-A, the health risks of male children, male teenagers, and female adults are higher than female children and female teenagers, and male adults. However, for drinking water sources WS-B, WS-C, WS-D, and WS-E, the health risks of female children, male teenagers, and female adults are higher than male children, female teenagers, and male adults. The highest health risks occurred in female children consuming drinking water from WS-D. The sensitivity analysis indicated that the concentration of As is the primary factor for carcinogenic risk of all the five water systems. The results obtained can provide meaningful information for risk managers in Jiangsu Province.

Public health risk of toxic metal(loid) pollution to the population living near an abandoned small-scale polymetallic mine

Small-scale mining activities in many developing countries have caused severe environmental issues to the surrounding areas, which ultimately threatened the health of local populations. Based on detailed characterization of the local drinking water and surface soil, as well as foodstuffs, this study comprehensively assessed the public health risk of toxic metal(loid)s to the population living in three villages surrounding an abandoned small-scale polymetallic mine in southern China. The agricultural soils contained elevated levels of Cu, Zn, As, Cd, and Pb, which originated from the mining district, and as expected, the locally cultivated rice and vegetables were contaminated by As, Cd, and Pb to varying extents. Arsenic occurred in both inorganic and organic forms in the rice and vegetables, with inorganic As (i-As) accounting for 82.2% (45.4-100%) and 94.7% (65.2-100%) of the total As contents in rice and vegetables, respectively. Results of health risk assessment indicate that the residents in the impacted villages had serious non-carcinogenic and carcinogenic risk. Dietary exposure to i-As and Cd through rice and vegetable consumption was the primary cause of non-carcinogenic risk, while i-As intake was the dominant contributor of carcinogenic risk. These findings suggest that significant environmental pollution by toxic metal(loid)s could result from small-scale metal mines, even after being abandoned, and the accumulation of the toxic metal(loid)s in food crops could pose significant health risk to the local residents. Immediate actions should be taken to discourage them from consuming the locally produced food crops, while long-term control measures for containment of toxic metal(loid) pollution are being developed, and high priority should be given to the remediation of Cd and As in the contaminated soils.

Total and Estimated Inorganic Arsenic Levels in Imported and Local Chicken Sold in Trinidad and Tobago

ABSTRACT

Arsenic contamination in chicken is a cause of concern because of the potential health problems that may arise. In Trinidad and Tobago, chicken consumption averages about 53.8 kg per person per year, and chicken accounts for 85% of all the meat consumed locally. Fourteen chicken samples of imported, locally grown, and local organically farmed chickens were obtained from poultry depots and local supermarkets and were analyzed in triplicate. The concentration of total arsenic in the imported chicken ranged from below the method detection limit (MDL) to 512.50 μg/kg, and the concentration in the locally produced chicken ranged between <MDL and 516.44 μg/kg. The estimated concentration of inorganic arsenic (iAs) in the imported chickens ranged between <MDL and 333.12 μg/kg, whereas in local chicken it ranged between <MDL and 335.68 μg/kg. The estimated daily intake (EDI) of iAs varies between 0 and 0.72 μg/kg/day. Five of the samples evaluated exceeded the tolerable limit of 0.3 μg/kg of body weight per day as set by the U.S. Environmental Protection Agency.

HIGHLIGHTS

Arsenic volatilization in roxarsone-loaded digester: Insight into the main factors and arsM genes

The extensive use of roxarsone (ROX) in livestock and poultry husbandry causes the production of arylarsenic-contaminated manure/wastewater. Anaerobic digestion is a conventional technique for livestock manure/wastewater treatment. However, the factors affecting arsenic volatilization are poorly understood in arylarsenic-loaded anaerobic reactors. The main factors such as ROX loading, exposure time of anaerobic granular sludge (AGS) to ROX, and volatile fatty acid (VFA) levels, affecting arsenic volatilization were investigated in this study. The results indicated that ROX loading of 5.70 mg-As·L^-1 triggered the maximum volatile arsenic yield of 6.78 ng-As·g^-1-VSS·d^-1, which was 4.95 times higher compared to the ROX-free assay. The conversion of ROX into inorganic arsenic was an essential step for arsenic volatilization. The 160-day and 270-day exposure of AGS to ROX caused 6-fold and 8-fold increase in volatile arsenic yield, respectively, compared to the 0-day exposure. With the longer-time exposure to ROX, AGS provided more available arsenic for volatilization and its arsenic-volatilizing capacity was significantly enhanced. VFA level was positively associated with arsenic volatilization (r = 0.832-0.950; p < 0.05). The abundance of arsM genes in AGS increased by 34.62-129.05% after the 100-day incubation, and was strongly correlated to arsenic volatilization. Based on these results, possible pathway of arsenic volatilization in ROX-loaded digesters were proposed. The result from this study improves a better understanding of the potential of arsenic volatilization in arylarsenic-contaminated environments.

Identification of an anaerobic bacterial consortium that degrades roxarsone

The degradation of roxarsone, an extensively used organoarsenic feed additive, occurs quickly under anaerobic conditions with microorganisms playing an important role in its degradation. Here, an anaerobic bacterial consortium that effectively degraded roxarsone was isolated, and its degradation efficiency and community changes along a roxarsone concentration gradient under anaerobic conditions were assessed. We used batch experiments to determine the roxarsone degradation rates, as well as the bacterial community structure and diversity, at initial roxarsone concentrations of 50, 100, 200, and 400 mg/kg. The results showed that roxarsone was degraded completely within 28, 28, 36, and 44 hr at concentrations of 50, 100, 200, and 400 mg/kg, respectively. The anaerobic bacterial consortium displayed considerable potential to degrade roxarsone, as the degradation rate increased with increasing roxarsone concentrations. Roxarsone promoted microbial growth, and in turn, the microorganisms degraded the organoarsenic compound, with the functional bacterial community varying between different roxarsone concentrations. Lysinibacillus, Alkaliphilus, and Proteiniclasticum were the main genera composing the roxarsone‐degrading bacterial community.

Land-use controls on nutrient loads in aquifers draining agricultural and mixed-use karstic watersheds

Agricultural nonpoint source pollution from the upper areas of the Upper Mississippi, Missouri, and Ohio River basins accounts for the majority of the excess nitrogen that leads to the Gulf of Mexico's hypoxic zone. However, agriculture landscapes across the USA, Europe, and China are undergoing major changes related to the proliferation of confined animal feeding operations (CAFOs) that account for a greater proportion of point source contamination. Mitigating long-term nutrient inputs at a large scale (Mississippi River Basin) requires understanding these microscale changes at the small watershed level (less than 100 km²). To assess the control of land-use and subsurface hydrological processes on nutrient fate and transport, temporal patterns in nutrient concentrations in a mixed land-use karstic watershed were analyzed. To assess the control of differential land-use sources on total inorganic nitrogen (TIN) loads within the watershed, 4 months of weekly water sampling was performed at a spring location and at two underground conduit locations. The observed temporal variations in nutrient concentrations are primarily associated with seasonal changes in land-use associated with corn growth. Data show that land-use sources explain much of the temporal variability of TIN at the spring when weighted against the hydrological factor. End-member-mixing analysis of dissolved organic carbon (DOC) shows a progressive increase in the contribution of DOC-enriched sources and a more labile form of carbon toward the harvest time. Overall, during high flow, nonpoint source infiltration from manure-fertilized croplands in the northern branch (NB) dominate DOC loads. Because conduit-dominated karstic aquifers are more susceptible to contamination from direct and fast (< 7 h) subsurface infiltration during late summer rainfall period (July to August), a slight advance in the timing of manure application could substantially reduce nutrient loads to local groundwater. A combined evaluation of subsurface hydrological processes and land-use factors controlling nutrients at the scale of small watersheds is crucial to developing site-specific nutrient management plans and managing the Gulf of Mexico's hypoxic zone.

Arsanilic acid contributes more to total arsenic than roxarsone in chicken meat from Chinese markets

Organoarsenicals have been used in poultry production for years, however, studies focused on roxarsone (ROX), with little attention to p-arsanilic acid (ASA). We assessed arsenic (As) concentration and speciation in chicken meat collected from 10 cities in China. The geometric mean for total As in 249 paired raw and cooked samples was 4.85 and 7.27 μg kg^-1 fw, respectively. Among 81 paired raw and cooked samples, ASA and ROX were detected in >90% samples, suggesting the prevalence of organoarsenical use in China. ASA contributed the most (45% on average) to total As in cooked samples, followed by As(V), DMA, As(III), and ROX (7.2-22%). ASA was found to contribute more to total As in chicken meat compared to ROX for the first time. Arsenic in chicken meat showed considerable geographic variation, with higher inorganic arsenic (iAs) being detected from cities with higher ROX and ASA, indicating that organoarsenical use increased iAs concentration in chicken meat. When health risk was estimated, dietary exposure to iAs would result in an increase of 3.2 bladder and lung cancer cases per 100,000 adults. The result supports the removal of organoarsenicals in poultry production from Chinese market and further supports its removal from the global markets.

China's Ban on Phenylarsonic Feed Additives, A Major Step toward Reducing the Human and Ecosystem Health Risk from Arsenic

Phenylarsonic feed additives were once widely used in poultry and swine production around the world, which brought significant and unnecessary health risk to consumers due to elevated residues of arsenic species in animal tissues. They also increased the risk to ecosystems via releases of inorganic arsenic through their environmental transformation. Out of concern for the negative impacts on human and ecosystem health, China, one of the world's largest poultry and swine producing countries, recently banned the use of phenylarsonic feed additives in food animal production. This ban, if fully enforced, will result in reduction of approximately 1160 cancer cases per year from the consumption of chicken meat alone, and avoid an annual economic loss of nearly 0.6 billion CNY according to our risk analysis. Furthermore, the inventory of anthropogenic arsenic emissions in China will be cut by approximately one-third with the phase-out of phenylarsonic feed additives. This ban is also expected to lead to significant reduction in the accumulation of arsenic in the soils of farmlands fertilized by poultry and swine wastes and, consequently, lower the accumulation of arsenic in food crops grown on them, which could have even greater public health benefits. But effective enforcement of the ban is crucial, and it will require detailed supervision of veterinary drug production and distribution, and enhanced surveillance of animal feeds and food products. Furthermore, control of other major anthropogenic sources of arsenic is also necessary to better protect human health and the environment.

Effect of roxarsone metabolites in chicken manure on soil biological property

Roxarsone (ROX), an organoarsenic feed additive, occurs as itself and its metabolites including As(V), As(III), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in animal manure. Animal manure improves soil biological property, whereas As compounds impact microorganisms. The integral influence of animal manure bearing ROX metabolites on soil biological quality is not clear yet. Herein, the effect of four chicken manures excreted by chickens fed with four diets containing 0, 40, 80 and 120 mg ROX kg^-1, on soil biological attributes. ROX addition in chicken diets increased total As and ROX metabolites in manures, but decreased manure total N, ammonium and nitrate. The elevated ROX metabolites in manures increased soil total As, As species and total N, and increased first and then decreased soil nitrate and nitrite, but did not affect soil ammonium in manure-applied soils. The promoting role of both soil As(III) and ammonium on soil microbial biomass carbon and nitrogen, respiration and saccharase activity, were exceeded or balanced by the inhibiting effect of soil nitrate. The suppression of soil catalase activity by soil As(V) was surpassed by the enhancement caused by soil nitrate and nitrite. Soil urease, acid phosphatase and polyphenol oxidase activities were not suitable bioindicators in the four manure-amended soils. Soil DMA did not affect soil biological properties, and MMA was not detectable in all manure-amended soils. The above highlights the complexity of joint influence of soil As and N on biological attributes. Totally, when ROX is used at allowable dose in chicken diet, soil biological quality would be suppressed in manure-amended soil.

Biotransformation of arsenic-containing roxarsone by an aerobic soil bacterium Enterobacter sp. CZ-1

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX) is an arsenic-containing compound widely used as a feed additive in poultry industries. ROX excreted in chicken manure can be transformed by microbes to different arsenic species in the environment. To date, most of the studies on microbial transformation of ROX have focused on anaerobic microorganisms. Here, we isolated a pure cultured aerobic ROX-transforming bacterial strain, CZ-1, from an arsenic-contaminated paddy soil. On the basis of 16S rRNA gene sequence, strain CZ-1 was classified as a member of the genus Enterobacter. During ROX biotransformation by strain CZ-1, five metabolites including arsenate (As[V]), arsenite (As[III]), N-acetyl-4-hydroxy-m-arsanilic acid (N-AHPAA), 3-amino-4-hydroxyphenylarsonic acid (3-AHPAA) and a novel sulfur-containing arsenic species (AsC₉H₁₃N₂O₆S) were detected and identified based on high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS), HPLC-ICP-MS/electrospray ionization mass spectrometry (ESI-MS) and HPLC-electrospray ionization hybrid quadrupole time-of-flight mass spectrometry (ESI-qTOF-MS) analyses. N-AHPAA and 3-AHPAA were the main products, and 3-AHPAA could also be transformed to N-AHPAA. Based on the results, we propose a novel ROX biotransformation pathway by Enterobacter. sp CZ-1, in which the nitro group of ROX is first reduced to amino group (3-AHPAA) and then acetylated to N-AHPAA.

Arsenic Concentrations, Speciation, and Localization in 141 Cultivated Market Mushrooms: Implications for Arsenic Exposure to Humans

Mushrooms accumulate arsenic (As), yet As concentrations, speciation, and localization in cultivated mushrooms across a large geographic distribution are unknown. We characterized 141 samples of nine species from markets in nine capital cities in China, with samples of Lentinula edodes, Pleurotus ostreatus, and Agaricus bisporus being analyzed for As speciation and localization. Total As concentrations ranged from 0.01 to 8.31 mg kg^-1 dw, with A. bisporus (0.27-2.79 mg kg^-1) containing the most As followed by P. ostreatus and L. edodes (0.04-8.31 and 0.12-2.58 mg kg^-1). However, As in A. bisporus was mostly organic including nontoxic arsenobetaine, while P. ostreatus and L. edodes contained mainly inorganic As (iAs). On the basis of in situ imaging using LA-ICP-MS, As in L. edodes was localized to the surface coat of the cap, while As in P. ostreatus was localized to the junction of the pileus and stipe. When As speciation and daily mushroom consumption (1.37 g d^-1 dw) are considered, daily mushroom consumption may result in elevated iAs exposure, with increased bladder and lung cancer rates up to 387 cases per 100000. Our study showed that market mushrooms could be a health risk to the general public so its production should be monitored.

Highly effective oxidation of roxarsone by ferrate and simultaneous arsenic removal with in situ formed ferric nanoparticles

Roxarsone (ROX) is used in breeding industry to prevent infection by parasites, stimulate livestock growth and improve pigmentation of livestock meat. After being released into environment, ROX could be bio-degraded with the formation of carcinogenic inorganic arsenic (As) species. Here, ferrate oxidation of ROX was reported, in which we studied total-As removal, determined reaction kinetics, identified oxidation products, and proposed a reaction mechanism. It was found that the apparent second-order rate constant (k_app) of ferrate with ROX was 305 M^-1s^-1 at pH 7.0, 25 °C, and over 95% of total As was removed within 10 min when ferrate/ROX molar ratio was 20:1. Species-specific rate constants analysis showed that HFeO₄^- was the dominant species reacting with ROX. Ferrate initially attacked AsC bond of ROX and resulted in the formation of arsenate and 2-nitrohydroquinone. The arsenate was simultaneously removed by ferric nanoparticles formed in the reduction of ferrate, while 2-nitrohydroquinone was further oxidized into nitro-1,4-benzoquinone. These results suggest that ferrate treatment can be an effective method for the control of ROX in water treatment.

Removal of Organoarsenic with Ferrate and Ferrate Resultant Nanoparticles: Oxidation and Adsorption

Many investigations focused on the capacity of ferrate for the oxidation of organic pollutant or adsorption of hazardous species, while little attention has been paid on the effect of ferrate resultant nanoparticles for the removal of organics. Removing organics could improve microbiological stability of treated water and control the formation of disinfection byproducts in following treatment procedures. Herein, we studied ferrate oxidation of p-arsanilic acid ( p-ASA), an extensively used organoarsenic feed additive. p-ASA was oxidized into As(V), p-aminophenol ( p-AP), and nitarsone in the reaction process. The released As(V) could be eliminated by in situ formed ferric (oxyhydr) oxides through surface adsorption, while p-AP can be further oxidized into 4,4'-(diazene-1,2-diyl) diphenol, p-nitrophenol, and NO₃^-. Nitarsone is resistant to ferrate oxidation, but mostly adsorbed (>85%) by ferrate resultant ferric (oxyhydr) oxides. Ferrate oxidation (ferrate/ p-ASA = 20:1) eliminated 18% of total organic carbon (TOC), while ferrate resultant particles removed 40% of TOC in the system. TOC removal efficiency is 1.6 to 38 times higher in ferrate treatment group than those in O₃, HClO, and permanganate treatment groups. Besides ferrate oxidation, adsorption of organic pollutants with ferrate resultant nanoparticles could also be an effective method for water treatment and environmental remediation.