The contribution of azo dyes to the mutagenic activity of the Cristais River

The natural anthraquinone dye emodin: Eco/genotoxicological characterization for aquatic organisms

Emodin is an anthraquinone secondary metabolite produced by several species of plants and fungi. Emodin is known for its pharmacological versatility, and, in the textile industry, for its good dyeing properties. However, its use in the textile industry can result in the formation and disposal of large volumes of wastewater. Emodin mutagenicity has been shown in bacteria and in human cells, but little is known about its possible toxic, genotoxic, or mutagenic effects in aquatic organisms. We have evaluated the eco/genotoxicity of emodin to aquatic organisms. Emodin was toxic to Daphnia similis (EC50 = 130 μg L-1) and zebrafish embryos (LC50 = 25 μg L-1). No toxicity was observed for Raphidocelis subcapitata, Ceriodaphnia dubia, or Parhyale hawaiensis. Additional biochemistry/molecular studies are needed to elucidate the toxic/mutagenic pathways of emodin in aquatic organisms. The PNEC value for emodin was 0.025 μg L-1. In addition to mutagenicity in the Salmonella/microsome assay, emodin was mutagenic in the micronucleus assay in the amphipod P. hawaiensis. Among the anthraquinone dyes tested to date, natural or synthetic, emodin was the most toxic to aquatic species.

Is natural better? An ecotoxicity study of anthraquinone dyes

The concept of sustainability has gained prominence in recent years, enhancing the need to develop products that are less harmful to the environment. Dyes are used by various industrial sectors and have a lot of market value; they are used on a large scale mainly by the textile industry that uses large volumes of water and is one of the main contributors to the contamination of water bodies. Some natural compounds, especially anthraquinones are re-emerging as possible alternatives to synthetic dyes, some of which are known for their toxic and/or mutagenic effects. The BioColour project (https://biocolour.fi/) which is interested in promoting the development of new alternative molecules to synthetic dyes, provided us highly purified anthraquinone dyes dermocybin and dermorubin (>98% purity) extracted from a specie of fungus Cortinarius sanguineus. Dyes were tested for their acute and chronic toxicity using different aquatic organisms. Dermorubin was not toxic to any of the organisms tested for the highest test concentration of 1 mg L-1 and it was the most promising dye. Dermocybin was toxic to Daphnia similis (EC50 = 0.51 mg L-1), Ceriodaphnia dubia (IC10 = 0.13 mg L-1) and Danio rerio embryos (extrapolated LC50 = 2.44 mg L-1). A safety limit, i.e, predicted no-effect concentration (PNEC) of 0.0026 mg L-1 was derived based on the toxicity of dermocybin. The PNEC value can be used to provide hazard information for future application in commercial dyeing processes. Then, we compared the toxicity of dermocybin and dermorubin with ecotoxicity data available in the literature on other anthraquinone dyes of natural and synthetic origin. Some natural dyes can be as toxic as synthetic ones, or more toxic when chronic effects are considered. Despite natural dyes being used since centuries past, there are few ecotoxicological studies available. This study is designed to help develop a more comprehensive understanding of their toxicological properties.

Investigating sensitization activity of azobenzene disperse dyes via the Direct Peptide Reactivity Assay (DPRA)

Azobenzene disperse dyes are the fastest-growing category of commercial dyestuffs and have been found in indoor house dust and in children's polyester apparel. Azobenzene disperse dyes are implicated as potentially allergenic; however, little experimental data is available on allergenicity of these dyes. Here, we examine the binding of azobenzene disperse dyes to nucleophilic peptide residues as a proxy for their potential reactivity as electrophilic allergenic sensitizers. The Direct Peptide Reactivity Assay (DPRA) was utilized via both a spectrophotometric method and a high-performance liquid chromatography (HPLC) method. We tested dyes purified from commercial dyestuffs as well as several known transformation products. All dyes were found to react with nucleophilic peptides in a dose-dependent manner with pseudo-first order kinetics (rate constants as high as 0.04 h-1). Rates of binding reactivity were also found to correlate to electrophilic properties of dyes as measured by Hammett constants and electrophilicity indices. Reactivities of polyester shirt extracts were also tested for DPRA activity and the shirt extracts with high measured abundances of azobenzene disperse dyes were observed to induce greater peptide reactivity. Results suggest that azobenzene disperse dyes may function as immune sensitizers, and that clothing containing these dyes may pose risks for skin sensitization.

Characterizing azobenzene disperse dyes and related compounds in house dust and their correlations with other organic contaminant classes

Azobenzene disperse dyes are the fastest-growing category of commercial dyestuffs and are implicated in the literature as potentially allergenic. In the indoor environment, these dyes may be shed from various textiles, including clothing and upholstery and accumulate in dust particles potentially leading to exposure in young children who have higher exposure to chemicals associated with dust due to their crawling and mouthing behaviors. Children may be more vulnerable to dye exposure due to their developing immune systems, and therefore, it is critical to characterize azobenzene disperse dyes in children's home environments. Here, we investigate azobenzene disperse dyes and related compounds in house dust samples (n = 124) that were previously analyzed for flame retardants, phthalates, pesticides and per- and polyfluoroalkyl substances (PFAS). High-resolution mass spectrometry was used to support both targeted and suspect screening of dyes in dust. Statistical analyses were conducted to determine if dye concentrations were related to demographic information. Detection frequencies for 12 target dyes ranged from 11% to 89%; of the dyes that were detected in at least 50% of the samples, geometric mean levels ranged from 32.4 to 360 ng/g. Suspect screening analysis identified eight additional high-abundance azobenzene compounds in dust. Some dyes were correlated to numerous flame retardants and several antimicrobials, and statistically higher levels of some dyes were observed in homes of non-Hispanic Black mothers than in homes of non-Hispanic white mothers. To our knowledge, this is the most comprehensive study of azobenzene disperse dyes in house dust to date. Future studies are needed to quantify additional dyes in dust and to examine exposure pathways of dyes in indoor environments where children are concerned.

ZnO-based heterojunction catalysts for the photocatalytic degradation of methyl orange dye

In this study, a variety of ZnO-based heterojunctions with disparate wt.% doping of WO3 and BiOI have been prepared for the photodestruction of methyl orange (MO) dye in aqueous solution. The composites were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, optical studies, and nitrogen adsorption-desorption isotherms. The SEM images revealed non-uniform surfaces of the ZnO-BiOI based composites while mostly nodular morphology was observed for all three samples of ZnO-WO3. As the WO3 loading increased, more clustering was detected. The analysed samples exhibited characteristic peaks representative of the triclinic phase of WO3 and the hexagonal wurtzite structure of ZnO, while the diffractogram observed from the materials displayed distinct peaks corresponding to the crystalline phases of both BiOI and ZnO in their pure forms. Further evidence of the samples' characteristics includes the presence of distinct crystalline patterns without any impurity peaks, a red shift in the absorption spectra of the heterostructure, the detection of only the reference elements, and mostly Type IV isotherm adsorption. This study identified the ZnO-[10%]BiOI and ZnO-[10%]WO3 heterojunctions as the best performing photocatalysts, as MO was completely destroyed in 120 and 90 min, respectively. Thus, confirming 10% wt. as the optimal doping concentration for the best photo-activity in this study. The impact of varying process parameters demonstrates that at an elevated photocatalyst mass of 40 mg, both heterojunctions effectively degraded MO. The photodegradation efficiency of MO was more pronounced in strong acidic conditions (pH 2) when compared to high alkaline conditions (pH 11) for the ZnO-[10%]BiOI heterostructure. However, a decrease in performance was observed for both strong acidic and high alkaline pH values when the ZnO-[10%]WO3 heterostructure was applied. The kinetic analysis of the photodegradation study reveals that all the photodegradation experiments can be represented by the pseudo-first-order kinetic model. The findings from this investigation propose that the ZnO-[10%]BiOI heterojunction photocatalyst holds significant potential for the effective treatment of dye-contaminated wastewater.

Assessment of the superior photocatalytic properties of Sn2+-containing SnO2 microrods on the photodegradation of methyl orange

A microporous Sn2+-containing SnO2 material presenting microrod morphology and a surface area of 93.0 m2 g-1 was synthesized via a simple hydrothermal route. Sn2+ ions were detected in the interior of the material (15.8 at.%) after the corrosion of a sample through sputtering. The material's optical properties have demonstrated the absorption of a considerable fraction of visible light up to wavelengths of 671 nm, due to the presence of Sn2+ states in the material's band structure. The analysis of the internal crystalline structure of a single microrod was carried out with the aid of a focused ion beam microscope and indicated that the material is mesocrystalline down to nanoscale level. It was proposed that the Sn2+ ions occupy intergranular sites in the highly defective crystalline structure of the material and that Sn2+ states, as well as its relatively large surface area, are responsible for the material's superior photoactivity. The synthesized material was tested as a photocatalyst to decompose hazardous contaminants in water. The photocatalytic performance of the material was much higher than those of commercial TiO2 and SnO2 materials, decomposing nearly all methyl orange (an azo-dye model) content in water (10 mg L-1) in 6 min under UV irradiation for a photocatalyst dose of 5.33 g L-1. The photodegradation of methyl orange was also verified under visible light.

Production of single-component cellulose-based hydrogel and its utilization as adsorbent for aqueous contaminants

The growing concern for the environment has resulted in renewed interest in bio-based resources. This study aims to produce a hydrogel adsorbent from cellulose and examine its adsorption performance. In pursuit of this goal, we report a simple one-pot synthesis of cellulose acetate sulfate (CAS), followed by the formation of CAS hydrogels and their subsequent adsorption performances. The CAS includes both hydrophilic and hydrophobic functional groups, enable the formation of a single-component hydrogel through intermolecular interactions in deionized water. The thermal reversibility of CAS hydrogels makes them easily processable into various shapes. The durability of the CAS hydrogel adsorbents can be improved by introducing divalent cations (e.g., Ca²⁺), which create ionically crosslinked hydrogels. The ionically a crosslinked CAS hydrogel adsorbent exhibits a maximum adsorption capacity of 245 mg/g for methylene blue (MB) at 23 °C and a pH of 7. The adsorption behavior of MB on the CAS hydrogel follows both the pseudo-second-order model and the Langmuir adsorption isotherm model. Furthermore, the CAS hydrogel adsorbent maintains a 70 % removal ratio after five cycles. The simplicity of synthesis and hydrogel formation opens up new possibilities for producing and utilizing cellulose-based hydrogels as adsorbents for aqueous contaminants.

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Using 3D printed magnetic platform as support for screen printed electrode applied for p-toluenediamine detection in biological fluid and water samples

The present work reports the development and application of a new electrochemical sensor for the determination of low concentration levels of p-toluenediamine (PTD) in biological fluids and surface water samples. The proposed sensor was developed using a 3D-printed magnetic device as platform for carbon screen printed electrode (CSPE) modified by magnetic nanoparticles functionalized with carboxylic groups and l-cysteine (MNP-CA-CYS). The results obtained from the morphological and electrochemical characterizations of the sensing platform enabled us to confirm the success of the sensor functionalization with l-cysteine and to have a better understanding of the electrochemical behavior and preconcentration of PTD on the electrode surface. PTD oxidation occurred at 0.24V on MNP-CA-CYS and the mechanism recorded an increase of 51.0% in anodic peak current. Under optimized conditions, the square wave voltammograms obtained for the electrode modified by 40.0 μL MNP-CA-CYS suspension at 1.0 mg mL^-1, with accumulation time of 3 min, presented an analytical curve with linear range of 8.00 × 10^-7 to 8.00 × 10^-5 mol L^-1, represented by the equation Iap = (0.383 ± 0.011)[PTD] - (8.112 ± 0.07) × 10^-8 (R² = 0.9994), and detection and quantification limits of 8.53 × 10^-8 and 2.56 × 10^-7 mol L^-1, respectively. Finally, the proposed method was validated through comparison with high performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique and was successfully applied for PTD determination in samples of surface water, tap water, fetal bovine serum and artificial urine.

Electrically conductive TiO2/CB/PVDF membranes for synchronous cross-flow filtration and solar photoelectrocatalysis

Combining photocatalysis (PC) and membrane filtration (MF) has emerged as an attractive technology for water purification, however, the water purification efficiency and membrane fouling are still challenging. Herein, we report a novel photoelectrocatalytic (PEC) membrane mediated by a ternary polyvinylidene fluoride (PVDF)-carbon black (CB)-TiO₂ composite conductive membrane synthesized by a phase inversion method assisted by the mixed surfactants of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). The resultant electrically conductive TiO₂/CB/PVDF membrane features a homogeneous surface with obvious pore size of 20-150 nm, a thickness ∼116 μm, and an average resistivity as low as ∼3.165 Ω∙m. The cooperation of PVP and SDS surfactants dramatically improves the organic-inorganic interactions and thus eventually enhances the porosity, stability of porous structure, mechanical stability, and conductivity and electrochemical properties of the hybrid membrane. Upon the solvent evaperation of the wellblended casting solution and the phase inversion, TiO₂/CB preferentially exist on the surface of PVDF membrane, enabling the efficient PEC degradation of organic pollutants. The synergistic coupling of TiO₂ and CB in PVDF membrane results in efficient PEC properties with bi-functional membrane antifouling and enhanced water purification in azo dyes decolorization under the stationary mode and in our lab-made continuous cross-flow PEC system, superior to those by photocatalysis and electrocatalysis. The developed synchronous MF and PEC system mediated by the conductive TiO₂/CB/PVDF membrane proves to a feasible route to improving the self-cleaning properties of the polymer membrane while simultaneously increasing the water decontaminating efficiency.

Impact of textile dyes on health and ecosystem: a review of structure, causes, and potential solutions

The rapid growth of population and industrialization have intensified the problem of water pollution globally. To meet the challenge of industrialization, the use of synthetic dyes in the textile industry, dyeing and printing industry, tannery and paint industry, paper and pulp industry, cosmetic and food industry, dye manufacturing industry, and pharmaceutical industry has increased exponentially. Among these industries, the textile industry is prominent for the water pollution due to the hefty consumption of water and discharge of coloring materials in the effluent. The discharge of this effluent into the aquatic reservoir affects its biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and pH. The release of the effluents without any remedial treatment will generate a gigantic peril to the aquatic ecosystem and human health. The ecological-friendly treatment of the dye-containing wastewater to minimize the detrimental effect on human health and the environment is the need of the hour. The purpose of this review is to evaluate the catastrophic effects of textile dyes on human health and the environment. This review provides a comprehensive insight into the dyes and chemicals used in the textile industry, focusing on the typical treatment processes for their removal from industrial wastewaters, including chemical, biological, physical, and hybrid techniques.

Synthesis and characterization of novel molybdovanadophosphoric acid supported kaolin hybrid catalyst for Chromotrope 2R dye degradation in water

The present study provides a complete perspective of recyclable molybdovanadophosphoric acid immobilized on kaolin (MVPA/Kaolin), a hybrid material for catalytic degradation of the dye, Chromotrope 2R in water under mild reaction conditions. Novel MVPA/Kaolin was synthesized with an advanced impregnation method. The material was characterized with PXRD, FTIR, ICP-OES, SEM–EDX, TEM, TGA, surface area, porosity, and 31P NMR measurements. The material that can be classified as a Keggin type catalyst, could be used for hydrogen peroxide oxidation of aromatic azo (–N=N–) dyes with –OH and –SO3H functional groups. The degradation showed excellent conversion of 99.1% under optimum conditions of normal pressure and 60 °C temperature. Products like malonic acid and oxalic acid have been identified as the final products with GC–MS analysis. The present work has demonstrated the application of a simple and effective catalyst for degradation of azo dyes and the catalyst had the reusability capacity of up to six cycles without loss in performance.

Porous NH2-MIL-101(Fe) metal organic framework for effective photocatalytic degradation of azo dye in wastewater treatment

The porous iron-based metal organic frameworks (NH₂-MIL-101(Fe)), which consists of 2-amino benzene dicarboxylic acid (H₂BDC-NH₂) and ferrous ions were synthesized through one-step hydrothermal method. The surface area and pore volume of as-synthesized NH₂-MIL-101(Fe) were 66.48 m²/g and 0.09 cm³/g, respectively. The excellent photocatalytic performance endows NH₂-MIL-101(Fe) to generate hydroxyl radical (•OH), which then acting as efficiently active sites for azo dye degradation in wastewater. Meanwhile, the outstanding stability ability of NH₂-MIL-101(Fe) indicates the potential candidate for wastewater treatment.

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Porous iron-based metal organic frameworks (NH₂-MIL-101(Fe)) were successfully fabricated via simple one-pot hypothermal reaction.

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The as-synthesized NH₂-MIL-101(Fe) has high surface area ​and outstanding stability ability.

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Remarkable azo dye degradation performance of NH₂-MIL-101(Fe) in wastewater was obtained.

Effect of the bio-inspired modification of low-cost membranes with TiO2:ZnO as microbial fuel cell membranes

Microbial fuel cells (MFCs) are a novel technique for converting biodegradable materials into electricity. In this study, the efficiency of mixed crystal (TiO₂:ZnO) as a membrane modifier of a low-cost, antifouling and self-cleaning cation exchange membrane for MFCs was studied. The modification was prepared using polydopamine (PDA) as the bio-inspired glue, followed by gravity deposition of a mixture of catalyst nanoparticles (TiO₂:ZnO 0.03%, 1:1 ratio) as anti-biofouling agents. The effects of the membrane modification were evaluated in terms of power density, open circuit potential, coulombic efficiency, anti-biofouling properties and also color and COD removal efficiency. The results showed that the use of the PDA-modified membrane and a mixture of catalysts facilitated the transfer of cations released during the oxidation process in the anodic compartment of the MFC, which increased the power generation in the MFC by 2.5 times and 5.7 times the current compared to pristine and PDA pristine membranes, decreased the MFC operating cycle time from 5 to 3 days, doubled the lifetime of the membranes and demonstrated higher COD removal efficiency and color removal. Finally, SEM and AFM analysis showed that the modification significantly minimized surface fouling. The modified membranes in this study proved to be a potential alternative to the expensive membranes currently used in MFCs, furthermore, this modification could be an interesting alternative modification for other potential membranes for use in MFCs, due to the fact that the catalyst activation was only performed with visible light (artificial and solar), which could decrease operating costs.

Integrated experimental and theoretical insights for Malachite Green Dye adsorption from wastewater using low cost adsorbent

Water pollution is one of the problems that threaten humanity, and to confront it with only experimental procedures is not enough. It is necessary to integrate both practical methods and theoretical calculations to achieve decontamination with the most accurate interpretation. Hence, discussing the experimental mechanism study of Malachite Green (MG) dye adsorption with the help of the application of density functional theory (DFT) calculations is the main goal of this article. The experimental results affirmed that the preparation of γ-Al₂O₃ by precipitation method using (NH₄)₂CO₃ improved the porosity, the surface capability, and the adsorbent capacities (q_max = 210 mg/g) at optimum condition compared with the previous studies. Kinetic and equilibrium studies showed that the adsorption follows the pseudo-second-order model and Freundlich isotherm model, respectively. Also, the calculated and observed thermodynamic parameters exerted positive values of ΔH° and ΔS°, which translates into an endothermic process with increasing disorder of the system. Theoretical calculations at DFT- B3LYP/6-31G (d,P) level of theory were calculated to show the selectivity of using the cationic form of MG in the experimental measurements to find the interaction mechanism. The electronic structure and intramolecular charge transfer of MG, its cationic form and the complex of MG-Al were investigated theoretically at the B3LYP/6-31 G (d,p) level of theory. The equilibrium geometries of MG, its cationic form and the complex of MG-Al were determined, and it was found that these geometries are non-planar. The E_HOMO and E_LUMO energies can be used to calculate the global properties; chemical hardness (η), softness (S) and electronegativity (χ). The calculated non-linear optical parameters (NLO) of the studied compounds, the electronic dipole moment (μ), first-order hyperpolarizability (β), the hyper-Rayleigh scattering (β_HRS) and the depolarization ratio (DR), showed promising optical properties. Finally, the computational and the experimental results indicated that the adsorption efficiency of MG from wastewater was directly associated with the dye electrophilicity power.

Analysis and effective separation of toxic pollutants from water resources using MBBR: Pathway prediction using alkaliphilic P. mendocina

Azo dyes are highly toxic, which acts as a notable mutagen and carcinogen. This has a significant effect on human health, plants, animals, aquatic and terrestrial environments. Thus, the degradation of the azo dyes is exclusively studied using the conventional methods of which biodegradation is an eco-friendly approach. Hence, the present study is focused on the elucidation of reactive mixed azo dye degradation pathway using MBBR and laccase enzyme produced by an alkaliphilic bacterium P. mendocina. Synthetic wastewater treatment performed using MBBR was very effective which reduced the COD and BOD to 90 mg/L and 460 mg/L. The potential degrader P. mendocina was isolated and laccase enzyme was screened. Finally, the degradation pathway was elucidated. The in silico toxicity analysis predicted Reactive Red and Reactive Brown as developmental toxicants during Reactive Black as Developmental non-toxicant. Docking studies were performed to understand interaction of laccase with compounds evolved from dyes.

Red Tomato Products as an Alternative to Reduce Synthetic Dyes in the Food Industry: A Review

Most dyes used in the food industry are synthetic and can be a health hazard. Red tomato may serve as a natural alternative dye to replace synthetic colorants. This study aimed to review the literature on the addition of red tomato products (powder tomato, paste, freeze-dried, tomato peel powder, tomato pomace) to reduce the usage of synthetic dyes in the food industry. Red tomato products have been used as coloring in pasta, bologna, sausages, cookies, crackers, macaroons, hamburgers, breads, muffins, cheeses, and nuggets. The trans-cis isomerization of lycopene by oxidative processes directly affects the color of the pigment. The lycopene contained in tomato has antioxidant activity and could reduce or eliminate other oxidants and/or synthetic preservatives in food. Moreover, tomatoes in foods have high sensory scores, nutritional appeal, and marketing potential. However, its use as a food colorant has been not extensively explored. Therefore, further studies are still required, especially on the stability of carotenoids in tomatoes used in processed foods.

Assessment of the compounds formed by oxidative reaction between p-toluenediamine and p-aminophenol in hair dyeing processes: Detection, mutagenic and toxicological properties

Previous studies have demonstrated the presence of precursors and coupling agents in wastewater from hair dyeing processes. The complex reaction involved in the oxidation of these compounds can generate extremely hazardous sub-products, leading to an increase in the mutagenicity and toxicity of wastewater. Without proper treatment, this highly toxic wastewater may find its way into the drinking water treatment plant. The present work aimed to investigate the main products generated after the oxidation reaction involving p-toluenediamine (PTD) and p-aminophenol (PAP) - precursors that widely used in the composition of commercial permanent hair dyes, under experimental conditions close to the routine hair dyeing process (in the presence and absence of hydrogen peroxide in ammoniacal medium), using spectroscopic techniques. The study also investigated the mutagenicity and toxicity of the products formed in the hairdressing wash water and conducted detection analysis to determine the presence of the precursors and Bandrowski's Base Derivative (BBD) in samples of wastewater, surface and drinking water using HPLC-DAD and linear voltammetry techniques. Based on this investigation, we identified several PTD and PAP self-oxidation products and eleven sub-products derived from the reaction between PTD and PAP. Assays conducted using Salmonella typhimurium YG1041, with and without activation-induced rat liver metabolism (S9), indicated mutagenicity of the reaction products in concentrations above 10.0 μg μL^-1. The concentrations of PTD, PAP, and several reactions and oxidation products of these precursors were detected in wastewater and water samples.

Characterizing azobenzene disperse dyes in commercial mixtures and children's polyester clothing

Azobenzene disperse dyes are the fastest-growing class of dyestuffs, yet little is known about dye occurrences, sources, and transformations; azo dyes are also underrepresented in chemical standard catalogs, molecular databases, and mass spectral libraries. Many azo dyes are known to have sensitization, mutagenic, and carcinogenic properties. To fill these knowledge gaps, azo dyes were purified from dyestuffs by Soxhlet extraction and flash chromatography and characterized using ultra-high-performance liquid chromatography (UHPLC) coupled to a high resolution Orbitrap Fusion Lumos mass spectrometer operated in positive electrospray ionization mode, as well as by ¹H and ¹³C NMR. Data were analyzed to identify likely chemical formulas and structures using a weight-of-evidence approach with multiple open-source, in silico computational mass spectrometry tools. Nineteen total azobenzene dyes were detected in dyestuffs via a non-targeted analysis approach; the azobenzene dyes Disperse Blue 79:1, Disperse Blue 183:1, Disperse Orange 44, Disperse Orange 73, Disperse Red 50, Disperse Red 73, and Disperse Red 354 were purified from raw dyestuffs. Samples of children's polyester clothing were then analyzed likewise. In clothing, 21 azobenzene disperse dyes were detected, 12 of which were confirmed and quantified via reference standards. Individual dyes in apparel were quantified at concentrations up to 9230 μg dye/g shirt, with geometric means ranging 7.91-300 μg dye/g shirt. Total dye load in apparel was quantified at up to 11,430 μg dye/g shirt. This research supported the development of reference standards and library mass spectra for azobenzene disperse dyes previously absent from standard and spectral libraries. By analyzing the scope and quantities of azo dyes in children's polyester apparel, this study will facilitate a more robust understanding of sources of these potentially allergenic and mutagenic compounds.

Mutagenicity of a novel 2-phenylbenzotriazole (non-chlorinated 2-phenylbenzotriazole-9) in mice

Dinitrophenylazo dyes can form 2-phenylbenzotriazoles (PBTAs) in the textile dyeing process upon the addition of chemical reducing agents. Some dinitrophenylazo dyes, as well as their respective reduced (non-chlorinated) and chlorinated PBTAs, are now found in rivers owing to wastewater from textile plants. This study aimed to investigate the genotoxicity of a new PBTA derived from C.I. Disperse Violet 93 azo dye, namely non-Cl PBTA-9. Primary DNA damage in the blood, liver, and colon cells, micronucleated cells in the bone marrow, and gene expression (NAT2, CYP1A1, TRP53, and CDKN1A) in liver cells were observed in mice, at acute oral exposure (gavage) doses of 5, 50, and 500 μg/kg body weight (b.w.). The non-chlorinated PBTA-9 caused DNA damage in the blood and liver (at 500 μg/kg b.w.) and in colon cells (at 5, 50, and 500 μg/kg), and increased the frequency of micronucleated cells in the bone marrow (at 5 and 50 μg/kg). No histological alterations or gene expression changes were observed. In conclusion, in vivo exposure to non-chlorinated PBTA-9 induced genetic damage in various rodent tissues, corroborating results previously obtained from the Ames test. Because this compound has been detected in rivers, exposure to humans and biota is a major concern.

Application of QSAR for the identification of key molecular fragments and reliable predictions of effects of textile dyes on growth rate and biomass values of Raphidocelis subcapitata

The current quantitative structure-activity relationship (QSAR) study seeks to explore the underlying causes of fluctuations in growth rate and biomass of microalgae mainly due to textile dyes. The derived QSAR models cover two endpoints: ErC50 (growth rate) and EbC50 (biomass) of Raphidocelis subcapitata. In order to extract the structural features involved, multiple PLS (partial least squares) models have been developed with easy to interpret and uncomplicated 2D descriptors having proper physico-chemical meaning. These descriptors were calculated from Dragon, SiRMS, and PaDEL-descriptor software. Then, the models were developed initially using stepwise regression followed by partial least squares (PLS) regression, and the model development procedure for both the endpoints (ErC50 and EbC50) followed the stringent Organization for Economic Cooperation and Development (OECD) rules. Later on, the model validation was carried out with statistically significant and internationally accepted metrics (both internally and externally) in both the cases. Next, we have used the "Intelligent Consensus Predictor" tool (available from http://teqip.jdvu.ac.in/QSAR_Tools/DTCLab/) to test the prediction quality with an "intelligent" approach to select multiple models. The estimated prediction quality for the appropriate test sets reveals that the consensus models (CM) surpass the quality shown by individual models (IM) for both the endpoints (ErC50 and EbC50). Finally, the developed models were able to identify the major contributing features (hydrophobic units, unsaturation, saturation, electronegativity, branched atoms and charged fragments) related to aquatic toxicity of textile dyes.

Visible Light-Driven Photocatalytic Activity and Kinetics of Fe-Doped TiO2 Prepared by a Three-Block Copolymer Templating Approach

Fe-doped titania photocatalysts (with 1, 2.5, and 3.5 wt. % Fe nominal content), showing photocatalytic activity under visible light, were prepared by a soft-template assisted sol-gel approach in the presence of the triblock copolymer Pluronic P123. An undoped TiO2 photocatalyst was also prepared for comparison. The photocatalysts were characterized by means of X-ray powder Diffraction (XRPD), Quantitative Phase Analysis as obtained by Rietveld refinement, Diffuse Reflectance (DR) UV-Vis spectroscopy, N2 adsorption/desorption at -196 °C, electrophoretic mobility in water (ζ-potential), and X-ray photoelectron spectroscopy (XPS). The physico-chemical characterization showed that all the samples were 100% anatase phase and that iron was present both in the bulk and at the surface of the Fe-doped TiO2. Indeed, the band gap energy (Eg) decreases with the Fe content, with Tauc's plot determined values ranging from 3.35 (undoped TiO2) to 2.70 eV (3.5 wt. % Fe). Notwithstanding the obtained Eg values, the photocatalytic activity results under visible light highlighted that the optimal Fe content was equal to 2.5 wt. % (Tauc's plot determined Eg = 2.74 eV). With the optimized photocatalyst and in selected operating conditions, under visible light it was possible to achieve 90% AO7 discoloration together with a TOC removal of 40% after 180 min. The kinetic behavior of the photocatalyst was also analyzed. Moreover, the tests in the presence of three different scavengers revealed that the main reactive species are (positive) holes and superoxide species. Finally, the optimized photocatalyst was also able to degrade phenol under visible light.

Persistent organic and inorganic pollutants in the effluents from the textile dyeing industries: Ecotoxicology appraisal via a battery of biotests

Today, the textile industry is considered as a leading economic sector in Tunisia. However, this sector demands a huge volume of water and a wide spectrum of chemicals, which is converted into potentially toxic wastewater leading to environmental perturbation and human health toxicity. Assessment of the environmental risks associated with textile wastewater becomes a necessity. In this study, textile dyeing wastewater samples were collected before and after the physico-chemical treatment carried out by textile companies located in Monastir-city-Tunisia and subjected to chemical analyzes in order to determine their physicochemical characteristics and the content of metals and textile dyes. The ecotoxicological assessment was performed using four organisms, namely Selenastrum capricornutum, Vibrio fischeri, Daphnia magna and Lepidium sativum, to represent different trophic levels. Based on chemical data, some physicochemical parameters (e.g. TSS, COD and TSS levels) and metals (e.g. Cr, Hg and Sb) in the textile dyeing effluents were revealed not in compliance with the Tunisian standard. Moreover, high quantities of three disperse dyes have been detected even in the textile dyeing wastewater samples before and after treatments. The ecotoxicological data confirmed that the textile dyeing influents displayed toxic effects to all the test organisms, with Selenastrum capricornutum being the most sensitive organism. While, the above toxic effects were decreased slightly when evaluating the treated effluents. Metals and textile disperse dyes could be associated with the observed toxic effects of the textile influents and effluents. In fact, the treatment process applied by the evaluated companies was only partially efficient at removing metals, disperse dyes and effluent ecotoxicity, suggesting potential risks to aquatic biota. These findings emphasize the importance of applying integrated chemical and biological approaches for continuous evaluation of the toxicity of the treated effluents to predict hazards on the environment.

New benzotriazoles generated during textile dyeing process: Synthesis, hazard, water occurrence and aquatic risk assessment

Phenylbenzotriazoles (PBTA) can be generated unintentionally during textile dyeing factories by reduction of dinitrophenylazo dyes and their subsequent chlorination in disinfection process. Eight non-chlorinated PBTAs (non-Cl PBTA) and their related chlorinated PBTAs have been found in rivers and presented mutagenic activity. No data on their aquatic toxicity are available. In this work, two new phenylbenzotriazoles, non-Cl PBTA-9 and PBTA-9, derived from the dye C.I. Disperse Violet 93 (DV93) were synthesized and chemically/toxicologically characterized. Both compounds were more mutagenic than the parental dye in the Salmonella/microsome assay in the presence of metabolic activation (S9). Mutagenicity studies in vivo with mammals would confirm their potential hazard to humans. The two compounds were acutely toxic to Daphnia similis. We developed an analytical method to simultaneously quantify non-Cl PBTA-9, PBTA-9 and DV93 in river waters. Non-Cl PBTA-9 was found in sites under influence of textile effluents but at concentrations that do not pose risk to the aquatic life according to the P-PNEC calculated based on the acute toxicity tests. PBTA-9 was not detected in any samples analyzed. More studies on the aquatic toxicity and water occurrence of PBTAs should be conducted to verify the relevance of this class of compounds as aquatic contaminants.

A promising Ames battery for mutagenicity characterization of new dyes

When testing new products, potential new products, or their impurities for genotoxicity in the Ames test, the quantity available for testing can be a limiting factor. This is the case for a dye repository of around 98,000 substances the Max Weaver Dye Library (MWDL). Mutagenicity data on dyes in the literature, although vast, in several cases is not reliable, compromising the performance of the in silico models. In this report, we propose a strategy for the generation of high-quality mutagenicity data for dyes using a minimum amount of sample. We evaluated 15 dyes from different chemical classes selected from 150 representative dyes of the MWDL. The purity and molecular confirmation of each dye were determined, and the microplate agar protocol (MPA) was used. Dyes were tested at the limit of solubility in single and concentration-response experiments using seven strains without and with metabolic activation except for anthraquinone dyes which were tested with eight strains. Six dyes were mutagenic. The most sensitive was YG1041, followed by TA97a > TA98 > TA100 = TA1538 > TA102. YG7108 as well as TA1537 did not detect any mutagenic response. We concluded that the MPA was successful in identifying the mutagenicity of dyes using less than 12.5 mg of sample. We propose that dyes should be tested in a tiered approach using YG1041 followed by TA97a, TA98, and TA100 in concentration-response experiments. This work provides additional information on the dye mutagenicity database available in the literature.

Effects of biowaste-derived biochar on the electron transport efficiency during anaerobic acid orange 7 removal

In this study, different biochar (based on different pyrolytic temperatures and iron dosage) were prepared, characterized and used as individual additives for promoting acid orange 7 (AO7) anaerobic digestion. After X-ray diffraction (XRD), fourier transform infrared spectrometer (FTIR) characterization, 600 °C was proved to be the preferred temperature. Subsequently, biochar pyrolyzed at 600 °C with different iron dosage were added into five anaerobic reactors. Results showed that COD removal efficiency reached the maximum value (88.5%) with the presence of 600-1 biochar, which was 19.0% higher than control reactor (without biochar added). Further analysis indicated that more functional groups were found in 600-1 biochar could effectively improve the electron accepting capacities (EAC) and electron donating capacities (EDC). Combined with the enrichment of exoelectrogens related to syntrophic metabolism, it can be concluded that the addition of biochar could effectively improve the electron transfer efficiency which would be beneficial for AO7 removal.

Auramine dyes induce toxic effects to aquatic organisms from different trophic levels: an application of predicted non-effect concentration (PNEC)

The dyes Auramine and Auramine O are used in several industrial products, despite the scarce information regarding their ecotoxicity. The aim of the present study was to assess the acute and chronic toxicity of both dyes to aquatic organisms from different trophic levels (Raphidocelis subcapitata, Daphnia similis, Hydra attenuata, and Danio rerio) and calculate their predicted non-effect concentrations (PNEC). Auramine and Auramine O induced toxicity to all selected test organisms with L(E)C50 values ranging from 300 to 4800 ug/L. Both dyes induced inhibition in the growth rate of exposed algae, negatively affecting the reproduction of D. similis and induced deformities in H. attenuata (clubbed tentacles and shortened tentacles) and D. rerio (edemas, tail malformation and delay in yolk sac absorption). PNEC values of 0.92 μg/L and 4.0 μg/L were obtained for Auramine and Auramine O, respectively, based on results of the most sensitive test system (algae). Test results were analyzed using the Criteria of Reporting and Evaluating Ecotoxicity Data (CRED), confirming their reliability and relevance. Thus, PNEC values can be used in future risk assessments of those substances in freshwater systems.

Synthetic organic dyes as contaminants of the aquatic environment and their implications for ecosystems: A review

In recent years interest in the fate of chemical compounds in the aquatic environment has increased. There are many reports of the presence of chemical compounds such as pesticides, steroid hormones or antibiotics in the aquatic environment. At present, little is known about synthetic organic dyes as contaminants of water bodies. These dyes are omnipresent in many application areas from the textile, tannery, cosmetic and food industries to human and veterinary medicine. Their large-scale production and widespread applications have caused synthetic organic dyes to permeate into different compartments of water and soil environment. So far, dyes have been determined in environmental samples such as water, suspended particulate matters, sediment and wild fish. For this reason, they are considered micropollutants of aquatic ecosystems. Due to the toxicological properties and pharmacological activity of some synthetic organic dyes their occurrence in water bodies should be monitored. The hazard potential of synthetic organic dyes should be assessed, especially their influence on aquatic biota, not least because dyes in water ecosystems may pose a threat to animal or human health as higher-order consumers. This review collects scientific data considering application areas, toxicity, sources, environmental occurrence and the fate of synthetic organic dyes and the ecological implications of synthetic organic dyes presence in the total environment. Moreover, analytical methods for dye determination and methods for dye removal from wastewater are described.

Toxicokinetics of Brominated Azo Dyes in the Early Life Stages of Zebrafish (Danio rerio) Is Prone to Aromatic Substituent Changes

Brominated azo dyes (BADs) have been identified as predominant indoor brominated pollutants in daycare dust; thus, their potential health risk to children is of concern. However, the toxicities of BADs remain elusive. In this study, the toxicokinetics of two predominant BADs, Disperse Blue 373 (DB373) and Disperse Violet 93 (DV93), and their suspect metabolite 2-bromo-4,6-dinitroaniline (BDNA) was investigated in embryos of zebrafish (Danio rerio). The bioconcentration factor of DV93 at 120 hpf is 6.2-fold lower than that of DB373. The nontarget analysis revealed distinct metabolism routes between DB373 and DV93 by reducing nitro groups to nitroso (DB373) or amine (DV93), despite their similar structures. NAD(P)H quinone oxidoreductase 1 (NQO1) and pyruvate dehydrogenase were predicted as the enzymes responsible for the reduction of DB373 and DV93 by correlating time courses of the metabolites and enzyme development. Further in vitro recombinant enzyme and in vivo inhibition results validated NQO1 as the enzyme specifically reducing DB373, but not DV93. Global proteome profiling revealed that the expression levels of proteins from the "apoptosis-induced DNA fragmentation" pathway were significantly upregulated by all three BADs, supporting the bioactivation of BADs to mutagenic aromatic amines. This study discovered the bioactivation of BADs via distinct eukaryotic enzymes, implying their potential health risks.

Assessment of p-aminophenol oxidation by simulating the process of hair dyeing and occurrence in hair salon wastewater and drinking water from treatment plant

This work reports the study of oxidation reaction of p-aminophenol (PAP) in ammoniacal medium in dissolved atmospheric oxygen and hydrogen peroxide, simulating the process of hair dyeing with permanent dyes. The products formed, which included semi-quinoneimine radical, quinoneimine, dimers, trimers and tetramers, were identified by mass spectrometry, infrared spectroscopy, UV-vis spectrophotometry, and nuclear magnetic resonance of hydrogen. The process was found to involve an autoxidation mechanism. The mutagenicity of the products was carried out by Salmonella Typhimurium YG1041 assay, and the results indicated no mutagenic properties. The presence of PAP and its oxidative products in samples of wastewater collected from hairdressing salon effluent (WW), raw river water (RRW), and water inlet and outlet of drinking water treatment plant (DWTP) was analyzed by HPLC-DAD. PAP was detected in the collected samples of WW, water samples from DWTP (before and after treatment), at concentrations of 2.1 ± 0.5 mg L^-1, 1.9 ± 0.3 × 10^-3 mg L^-1 and 1.3 ± 0.2 × 10^-3 mg L^-1, respectively. The reaction products, including dimers, trimers and tetramers were identified only in the WW sample; this shows that both the precursor in the sample and its derivatives were released into the wastewater.

Herbul black henna (hair dye) causes cardiovascular defects in zebrafish (Danio rerio) embryo model

Herbul black henna (hair dye) have been widely used as cosmetic agents to temporarily change the color of hair. Their use was tremendously increased in the past decade. Especially, hair dye containing paraphenylenediamine (PPD) is extensively used globally because of its abundance and low cost. PPD, one of the main chemicals in hair dye, is known as a toxin. Hair dye has various adverse effects, including negative impacts on human health, especially during pregnancy and on aquatic environment. Although a large amount of dyes has been released into the environment, studies on environmental toxicity of these substances are still poorly understood. Hence, the main objective of this study is to evaluate the potential cardiovascular toxicological effects of hair dye on zebrafish (Danio rerio) embryo as a model. After exposing zebrafish embryos to various concentrations (100, 200, 300, 400, 500, and 600 μM), their cardiotoxicity and other teratogenic effects were examined for various exposure periods ranged from 24 to 96 hpf. As a result, the tested embryos could not survive over intervals of 48 h after 72 and 96 hpf at higher concentrations (300, 400, 500, and 600 μM), except the lower concentration cases (100 and 200 μM) some embryos were survived, respectively. However, hair dye increases mortality and decreases yolk stalk length, heart rate and severely affects heart looping in zebrafish embryos. In addition, the dye was observed to induce cardiovascular defects in transgenic Tg (fli1a:EGFP) and Tg (flk1:EGFP) zebrafish embryos at environmentally realistic dye concentrations. However, further study using bioassays is fundamentally required to predict the toxicity of hair dyes, aside from providing the information on their safe levels for living organisms. Therefore, the present results would be vital for the ecological risk assessment of hair dye, particularly for freshwater aquatic ecosystem and human health.

Visible light degradation of reactive black-42 by novel Sr/Ag-TiO2@g-C3N4 photocatalyst: RSM optimization, reaction kinetics and pathways

A novel Sr/Ag-TiO₂@g-C₃N₄ (SAT-C) composite catalyst was fabricated through a sol-gel method followed by hydrothermal process. The prepared catalyst was characterized well. The doped Ag and Sr nanoparticles played the crucial role as an electron transfer bridge and the surface plasmon resonance effect of Ag remarkably improved the charge separation efficiency and enhanced visible-light response towards reactive black (RB-42) degradation. The enhanced photogenerated charge separation resulted from the existed integrated electric field of heterojunction and the superposed light response from hybridization of TiO₂ and g-C₃N₄, Sr/Ag-TiO₂@g-C₃N₄ composites exhibited remarkably improved photocatalytic activities for degrading RB-42. Furthermore, the effect of various operational parameters on the photocatalytic process was systematically evaluated by using response surface methodology (RSM). The maximum degradation efficiency (95.6%) was observed under the optimal conditions ([RB-42]₀ = 20 mg/ L, [SAT-C]₀ = 0.2 g/ L, pH = 4.5 and t = 40 min) for RB-42. The RB-42 degradation kinetics was well studied under the optimal conditions. In addition, the main degradation products of RB-42 were identified by the LC/ESI-MS analysis.

Enhanced and selective adsorption of cationic dyes using novel biocompatible self-assembled peptide fibrils

Herein, bio-compatible self-assembled peptide fibrils have been developed for adsorption of organic pollutants for water remediation with high adsorption capacity. The different morphological motifs of self-assembled dipeptide Fmoc-FW-OMe was formulated using solvent modulation which was characterized by optical microscopy, SEM, XRD and FT-IR. Specifically, the fibril structures were used for selective adsorption of cationic dyes from aqueous solutions with exceptional adsorption capacity noted for crystal violet (625 mg/g). To understand the mechanism of dye adsorption, kinetics studies and adsorption isotherm studies were carried out which proved that the adsorption follows second order kinetics and Langmuir adsorption isotherm. The pH studies suggested that the adsorption of dye is much higher in alkaline conditions as compared to acidic conditions. The self-assembled peptide fibrils showed high reusability over five cycles with negligible effect on the dye adsorption capacity. Notably, this is the first report that discusses the application of self-assembled short peptide based fibrils for removal of dyes from waste water and in particular, it demonstrates the highest adsorption capacity reported for crystal violet dye so far. In general, this efficient capturing of dye pollutants with minimum usage of biocompatible adsorbents presents a simple and cost effective method for water remediation.

Mutagenicity as a parameter in surface water monitoring programs-opportunity for water quality improvement

Effect-based analyses are being recognized as excellent tools to a comprehensive and reliable water quality evaluation to complement physical and chemical parameters. The Salmonella/microsome mutagenicity test was introduced in the São Paulo State water quality-monitoring program in 1999 and waters from 104 sites used to the production of drinking water were analyzed. Samples were tested after organic extraction, using the microsuspension version of the Salmonella/microsome assay with strains TA98 and TA100 with and without S9-mammalian metabolic system. Of the 1720 water samples analyzed in 20 years, 20% were positive; TA98 was the most sensitive strain, detecting alone 99%. Results were presented in hazard categories to facilitate water managers' understanding and general public communication. Hot spots of mutagenicity were identified, and pollution sources investigated. A flow scheme with instructions of how to proceed in case of mutagenic samples was developed and implemented in the monitoring program. Enforcement actions were taken to reduce exposure of humans and aquatic biota to mutagenic compounds. The results presented provide scientific basis for the incorporation of the Salmonella/microsome assay in a regulatory framework, and to guide water-quality managers. The inclusion of a mutagenicity assay using standardized conditions proved to be an opportunity to improve the quality of water, and the strategy presented here could be applied by any environmental agency around the world. Environ. Mol. Mutagen. 61:200-211, 2020. © 2019 Wiley Periodicals, Inc.

Biodegradation of textile dye Reactive Blue 160 by Bacillus firmus (Bacillaceae: Bacillales) and non-target toxicity screening of their degraded products

The study was envisioned to evaluate the decolorization of Reactive Blue 160 (RB160) dye by using indigenous microbes. Contaminated soil from textile dye industry was collected from Noyyal river basin, Tamil Nadu, India. Potential dye degrading bacterial strain was recognized as Bacillus firmus by 16SrRNA gene sequencing analysis. RB160 dye (500 μg/ml) was effectively degraded by B. firmus and toxicological analyses were performed with RB160 and their degraded product. Phytotoxicity revealed that degraded product of RB160 into non-toxic nature by B. firms. Toxicity assays were carried out on root cells of Allium cepa and human skin cell line (CRL 1474). Toxicity analysis of A. cepa and cell line signifies that dye exerts toxic cause on the root cells and IC₅₀ values of RB160 showed toxic to human skin cell lines, while degradation products of the dye are moderately less in toxic. Zebrafish embryo toxicity also evaluated by RB160 and degraded product on phenotypic deformation, survival, hatching and heartbeat rate. However, RB160 with concentration of 500 μg/ml decrease in the survival, hatching, heartbeat rate and induced phenotypic alterations. In which, degraded products exhibited significant development in zebrafish embryos as compared to dye. Based on the studies effects of RB160 and capability of B. firmus can effectively degrade RB160, and their degraded products were harmless to the environments and aquatic system.

Life history and behavior effects of synthetic and natural dyes on Daphnia magna

Azo dyes are the largest class of dyes extensively used by industries despite their mutagenic potential for humans. As such, natural dyes have been reemerging as an important alternative to human safety. However, limited studies have focused on the effect of dyes on the environment, thus their ecotoxicological investigation is imperative. Here, we aimed to evaluate toxic effects induced by the synthetic azo dye Basic Red 51 (BR51) in comparison with natural dye erythrostominone (Ery) in the microcrustacean Daphnia magna, a standard organism used to assess the risk of chemicals to aquatic organisms. The colorless product formed after the photodegradation of Ery (DEry) was also evaluated, addressing an easy and low cost alternative for industrial effluent treatments. The results showed that both dyes are acutely toxic to D. magna. BR51 and Ery reduced the intrinsic rate of D. magna population increase, which generated fewer neonates per brood. BR51 also increased daphnids respiration rates. In contrast, DEry did not alter any of the analyzed parameters. No locomotor changes were observed when daphnids were exposed to sub-lethal concentrations of Ery or BR51. These results indicate that both dyes can induce deleterious consequences for daphnids including population level effects, but the natural dye Ery presents 100-fold lower toxicity in comparison with the azo dye BR51. Also, that photodegradation of Ery is an efficient method to reduce and prevent previously observed toxic effects, suggesting an inexpensive, fast and easy alternative for treatment of effluents containing this natural dye.

Microbial use for azo dye degradation-a strategy for dye bioremediation

Azo dyes are aromatic compounds with one to many -N=N- groups as well as the leading class of synthetic dyes utilised in commercial solicitations. Azo dyes, released in the environment through textile effluents, have hazardous effects on the aquatic as well as human life. Their persistence and discharge into the environment are becoming a global concern; thus, the remediation of these contaminants has acquired great attention. The current review comprehensively discusses some of the main aspects of biodegradation of azo dyes. A variety of physicochemical approaches has already been utilised for treatment of textile effluents counting filtration, coagulation and chemical flocculation. Though these conventional techniques are effective, yet they are lavish and also comprise formation of concentrated sludge that makes a secondary disposal problem. In this regard, microbial usage is an effective, economical, bio-friendly and ecologically benign approach.

Assessment of the autoxidation mechanism of p-toluenediamine by air and hydrogen peroxide and determination of mutagenic environmental contaminant in beauty salon effluent

The present work investigated the autoxidation reaction of p-toluenediamine (PTD) - a precursor - widely used in permanent hair dyeing formulation, under experimental conditions close to the hair dyeing process (oxygen and/or peroxide in ammoniacal medium), by chromatographic and spectroscopic techniques. In additional, evaluated the mutagenicity of the PTD oxidation products and the presence of PTD and this products in wastewater from beauty salon, as well as in surface water and drinking water using HPLC coupled to a diode array detector and linear scan voltammetry. Through this study, it was possible the identification of semi-quinonediimine, quinonediimine, dimers (derived from toluenediamine), and trimer radical identified as Bandrowski's Base derivative (BBD) formed during autoxidation of PTD. Salmonella Typhimurium YG1041 assay with and without metabolic activation induced rat-liver (S9) indicated mutagenic activity for BBD. Levels of PTD were determined by the standard addition method in samples collected from the wastewater of a beauty salon, as well as from the water before and after treatment in a drinking water treatment plant (DWTP) reached concentrations of 2.08 ± 0.21, 2.36 ± 0.10 × 10^-3, and 1.77 ± 0.13 × 10^-3 mg L^-1, respectively. In addition, linear sweep voltammetry was used to monitor the BBD found at the concentration of 1.59 ± 0.35 mg L^-1 in wastewater collected from the beauty salon.

Exposure to the azo dye Direct blue 15 produces toxic effects on microalgae, cladocerans, and zebrafish embryos

Aquatic pollution caused by dyes has increased together with the growth of activities using colorants such as the textile, leather, food, and agrochemicals industries. Because most popular azo dyes are synthesized from benzidine, a carcinogenic compound, a threat to aquatic biota could be expected. The use of single species for toxicity assessment provides limited data, so a battery of test organisms, including representatives of different trophic levels such as algae, zooplankters, and fish, could undoubtedly provide more information. Therefore, our study was aimed at evaluating the toxic effect of the azo dye Direct blue 15 (DB15) on a battery of bioassays using a primary producer (Pseudokirchneriella subcapitata), a primary consumer (Ceriodaphnia dubia), and a secondary consumer (Danio rerio). P. subcapitata was more sensitive to DB15 (IC₅₀ = 15.99 mg L^-1) than C. dubia (LC₅₀: 450 mg L^-1). In the algae exposed to DB15, chlorophyll-a and -b were significantly increased, and carotenoids were reduced. The concentrations of protein, carbohydrates, and lipids per cell in P. subcapitata exposed to all DB15 concentrations were significantly higher than that measured in control. At 25 mg L^-1 of DB15, survival, total progeny, and the number of released clutches were significantly decreased, and the start of reproduction was delayed in C. dubia. DB15 did not induce lethal or sublethal effects in D. rerio embryos at any of the tested concentrations from 24 to 72 h post-fertilization (hpf), but from 96 to 144 hpf, the larvae exposed to 100 and 500 mg L^-1 developed yolk sac edema, curved tail, and skeletal deformations. After 144 hpf, DB15 produced a significant increase in embryos without a heartbeat, as the concentration of dye raised. The textile-used, azo dye DB15, caused toxic effects of different magnitude on microalgae, cladocerans, and zebrafish embryos; for this reason, the discharge of this colorant into waterbodies should be regulated to prevent environmental impacts.

Abundances and concentrations of brominated azo dyes detected in indoor dust

Dust samples were collected from four indoor environments, including childcare facilities, houses, hair salons, and a research facility from the USA and were analyzed for brominated compounds using full scan liquid chromatography high-resolution mass spectrometry. A total of 240 brominated compounds were detected in these dust samples, and elemental formulas were predicted for 120 more abundant ions. In addition to commonly detected brominated flame retardants (BFRs), nitrogen-containing brominated azo dyes (BADs) were among the most frequently detected and abundant. Specifically, greater abundances of BADs were detected in indoor dusts from daycares and salons compared to houses and the research facility. Using authentic standards, a quantitative method was established for two BADs (DB373: Disperse Blue 373 and DV93: Disperse Violet 93) and 2-bromo-4,6-dinitroaniline, a commonly used precursor in azo dye production, in indoor dust. Generally, greater concentrations of DB373 (≤3850 ng/g) and DV93 (≤1190 ng/g) were observed in indoor dust from daycares highlighting children as a susceptible population to potential health risk from exposure to BADs. These data are important because, to date, targeted analysis of brominated compounds in indoor environments has focused mainly on BFRs and appears to underestimate the total amount of brominated compounds.