Does exposure to environmental 2,4-dichlorophenoxyacetic acid concentrations increase mortality rate in animals? A meta-analytic review

Does the atrazine increase animal mortality: Unraveling through a meta-analytic study

Atrazine is one of the most used herbicides in the world, although it is banned in several countries. Pollution of terrestrial and aquatic ecosystems represents a threat to non-target organisms, with various damages already reported in different species. However, there is controversy in studies on atrazine. The question of whether atrazine increases animal mortality is not yet clearly resolved. In this context, this study aimed to carry out a meta-analytic review, focusing on studies on environmental concentrations of the herbicide atrazine to evaluate its lethal effects on various animal species. We identified and analyzed 107 datasets through a selection process that used the Scopus, PubMed, and Web of Science (WoS) databases. A significant increase in the mortality rate of animals exposed to environmental concentrations of atrazine was observed. Nematodes, amphibians, molluscs, insects, and fish showed increased mortality after exposure to atrazine. Animals in the larval and juvenile stages showed greater susceptibility when exposed to different concentrations of atrazine. Furthermore, both commercial and pure formulations resulted in high mortality rates for exposed animals. Atrazine and other pesticides had a synergistic effect, increasing the risk of mortality in animals. There are still many gaps to be filled, and this study can serve as a basis for future regulations involving atrazine.

Novel 4-chlorophenoxyacetate dioxygenase-mediated phenoxyalkanoic acid herbicides initial catabolism in Cupriavidus sp. DL-D2

Microbial metabolism is an important driving force for the elimination of 4-chlorophenoxyacetic acid residues in the environment. The α-Ketoglutarate-dependent dioxygenase (TfdA) or 2,4-D oxygenase (CadAB) catalyzes the cleavage of the aryl ether bond of 4-chlorophenoxyacetic acid to 4-chlorophenol, which is one of the important pathways for the initial metabolism of 4-chlorophenoxyacetic acid by microorganisms. However, strain Cupriavidus sp. DL-D2 could utilize 4-chlorophenoxyacetic acid but not 4-chlorophenol for growth. This scarcely studied degradation pathway may involve novel enzymes that has not yet been characterized. Here, a gene cluster (designated cpd) responsible for the catabolism of 4-chlorophenoxyacetic acid in strain DL-D2 was cloned and identified, and the dioxygenase CpdA/CpdB responsible for the initial degradation of 4-chlorophenoxyacetic acid was successfully expressed, which could catalyze the conversion of 4-chlorphenoxyacetic acid to 4-chlorocatechol. Then, an aromatic cleavage enzyme CpdC further converts 4-chlorocatechol into 3-chloromuconate. The results of substrate degradation experiments showed that CpdA/CpdB could also degrade 3-chlorophenoxyacetic acid and phenoxyacetic acid, and homologous cpd gene clusters were widely discovered in microbial genomes. Our findings revealed a novel degradation mechanism of 4-chlorophenoxyacetic acid at the molecular level.

Biogenic magnetic nanocomposite of hydroxyapatite and dextran: synthesis, characterization, and enhanced removal of 2,4-D from aqueous environment

In this study, a biogenic magnetic nanocomposite, HAP@DEX@MNP, using hydroxyapatite from eggshell waste and dextran was developed to efficiently remove 2,4-D from aqueous solutions. The magnetic nano biocomposite underwent rigorous characterization using a comprehensive suite of analytical techniques, including FTIR, XRD, FESEM, EDX, TEM, and VSM. FTIR analysis was used to validate the existence of pivotal functional groups, such as phosphate, carbonyl, hydroxyl, and iron oxide. XRD analysis verified both the crystalline nature of hydroxyapatite and the successful integration of dextran and hematite within the composite structure. FESEM and EDX examinations provided valuable insights into the surface morphology and elemental composition. TEM observations elucidated the existence of nano-sized particles underscoring the unique structural characteristics of the nanocomposite. Batch adsorption experiments were conducted under optimized conditions, highlighting the critical role of pH 2 for efficient 2,4-D removal. The mechanisms driving the binding of 2,4-D to HAP@DEX@MNP were found to encompass diverse interactions, encompassing electrostatic forces, hydrogen bonding, π-π interactions, and van der Waals forces. Adsorption isotherm studies revealed both monolayer and multilayer adsorption, with the Langmuir and Freundlich models fitting well, indicating a maximal adsorption capacity of 217.39 µg/g at 25 °C. Kinetic investigations supported the pseudo-second-order model for efficient adsorption dynamics, and thermodynamic analysis emphasized the versatility of HAP@DEX@MNP across different temperatures. Importantly, the study highlighted the remarkable regenerative capacity of the nanocomposite using a 0.1 M NaOH solution, positioning it as an environmentally friendly option for water treatment. In conclusion, HAP@DEX@MNP holds significant potential for diverse applications in addressing global water treatment and environmental challenges.

Machine learning, conventional and statistical physics modeling of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide removal using biochar prepared from Vateria indica fruit biomass

The adsorption properties of 2,4-Dichlorophenoxyacetic acid (2,4-D) onto biochar, obtained through HCl-assisted hydrothermal carbonization process of Vateria indica fruits (VI-BC), were extensively studied using traditional and statistical physics approaches. The traditional adsorption investigations encompassed kinetics, equilibrium, and thermodynamics studies. Subsequently, the Hill statistical physics model was employed to interpret the mechanism. Also, artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) machine learning tools were successfully employed to model the adsorption data wherein both models had high prediction potential (R2 > 0.99). The outcomes demonstrated that the produced VI-BC exhibited remarkable adsorptive traits, having a considerable specific surface area (111.54 m2/g), pore size (5.89 nm), a variety of functional groups, and appropriate attributes for efficiently adsorbing 2,4-D. For 10 mg/L 2,4-D, at pH 2.0 and with 0.3 g/L dose, an impressive 91.67% adsorption efficiency was achieved within a 120-min. Pseudo-second-order model aptly depicted the kinetic behavior of 2,4-D adsorption, while the Freundlich model provided a more accurate representation of the isotherms. 2,4-D maximum adsorption capacity stood at 131.39 mg/g at 303 K. The Hill statistical physics model elucidated that the adsorption primarily occurred via physisorption mechanisms, involving electrostatic attractions, π-π conjugation, and pore filling. This conclusion was further substantiated by post-adsorption characterization of the VI-BC. Thermodynamic analysis indicated that the interactions between VI-BC and 2,4-D were favorable, spontaneous, and exothermic. The calculated low energy of adsorption (1.255 kJ/mol) and ΔH° value (-20.49 kJ/mol) further supported physisorption as the dominant mechanism. In summary, this study underscores the significant potential of the newly developed biochar as a promising alternative material for efficiently removing the 2,4-D herbicide from polluted environments.

A Ratiometric Biosensor Containing Manganese Dioxide Nanosheets and Nitrogen-Doped Quantum Dots for 2,4-Dichlorophenoxyacetic Acid Monitoring

Nanomaterials are desirable for sensing applications. Therefore, MnO2 nanosheets and nitrogen-doped carbon dots (NCDs) were used to construct a ratiometric biosensor for quantification of 2,4-dichlorophenoxyacetic acid. The MnO2 nanosheets drove the oxidation of colorless o-phenylenediamine to OPDox, which exhibits fluorescence emission peaks at 556 nm. The fluorescence of OPDox was efficiently quenched and the NCDs were recovered as the ascorbic acid produced by the hydrolyzed alkaline phosphatase (ALP) substrate increased. Owing to the selective inhibition of ALP activity by 2,4-D and the inner filter effect, the fluorescence intensity of the NCDs at 430 nm was suppressed, whereas that at 556 nm was maintained. The fluorescence intensity ratio was used for quantitative detection. The linear equation was F = 0.138 + 3.863·C 2,4-D (correlation coefficient R2 = 0.9904), whereas the limits of detection (LOD) and quantification (LOQ) were 0.013 and 0.040 μg/mL. The method was successfully employed for the determination of 2,4-D in different vegetables with recoveries of 79%~105%. The fluorescent color change in the 2,4-D sensing system can also be captured by a smartphone to achieve colorimetric detection by homemade portable test kit.

2,4-D Herbicide-Induced Hepatotoxicity: Unveiling Disrupted Liver Functions and Associated Biomarkers

2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide worldwide and is frequently found in water samples. This knowledge has prompted studies on its effects on non-target organisms, revealing significant alterations to liver structure and function. In this review, we evaluated the literature on the hepatotoxicity of 2,4-D, focusing on morphological damages, toxicity biomarkers and affected liver functions. Searches were conducted on PubMed, Web of Science and Scopus and 83 articles were selected after curation. Among these studies, 72% used in vivo models and 30% used in vitro models. Additionally, 48% used the active ingredient, and 35% used commercial formulations in exposure experiments. The most affected biomarkers were related to a decrease in antioxidant capacity through alterations in the activities of catalase, superoxide dismutase and the levels of malondialdehyde. Changes in energy metabolism, lipids, liver function, and xenobiotic metabolism were also identified. Furthermore, studies about the effects of 2,4-D in mixtures with other pesticides were found, as well as hepatoprotection trials. The reviewed data indicate the essential role of reduction in antioxidant capacity and oxidative stress in 2,4-D-induced hepatotoxicity. However, the mechanism of action of the herbicide is still not fully understood and further research in this area is necessary.

Complete biodegradation of the oldest organic herbicide 2,4-Dichlorophenoxyacetic acid by engineering Escherichia coli

After nearly 80 years of extensive application, the oldest organic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has caused many problems of environmental pollution and ecological deterioration. Bioremediation is an ideal method for pollutant treatment. However, difficult screening and preparation of efficient degradation bacteria have largely hindered its application in 2,4-D remediation. We have created a novel engineering Escherichia coli with a reconstructed complete degradation pathway of 2,4-D to solve the problem of screening highly efficient degradation bacteria in this study. The results of fluorescence quantitative PCR demonstrated that all nine genes in the degradation pathway were successfully expressed in the engineered strain. The engineered strains can quickly and completely degrade 0.5 mM 2, 4-D within 6 h. Inspiring, the engineered strains grew with 2,4-D as the sole carbon source. By using the isotope tracing method, the metabolites of 2,4-D were found incorporated into the tricarboxylic acid cycle in the engineering strain. Scanning electron microscopy showed that 2,4-D had less damage on the engineered bacteria than the wild-type strain. Engineered strain can also rapidly and completely remedy 2,4-D pollution in natural water and soil. Assembling the metabolic pathways of pollutants through synthetic biology was an effective method to create pollutant-degrading bacteria for bioremediation.

PCBs, PCNs, and PCDD/Fs in Soil around an Industrial Park in Northwest China: Levels, Source Apportionment, and Human Health Risk

The concentrations of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soil samples collected around an industrial park in Northwest China, to investigate the potential impacts of park emissions on the surrounding environment. The total concentration ranges of PCBs, PCNs, and PCDD/Fs in the soil samples were in 13.2-1240, 141-832, and 3.60-156 pg/g, respectively. The spatial distribution and congener patterns of PCBs, PCNs, and PCCD/Fs indicated that there might be multiple contamination sources in the study area, so source apportionments of PCBs, PCNs, and PCCD/Fs were performed by a positive matrix factorization model based on the concentrations of all target congeners together. The results revealed that these highly chlorinated congeners (CB-209, CN-75, and OCDF) might be derived from phthalocyanine pigments, the legacy of Halowax 1051 and 2,4-D products, which together contributed nearly half of the total concentration of target compounds (44.5%). In addition to highly chlorinated congeners, the local industrial thermal processes were mainly responsible for the contamination of PCBs, PCNs, and PCDD/Fs in the surrounding soil. The total carcinogenic risk of PCBs, PCNs, and PCDD/Fs in a few soil samples (0.22 × 10-6, 0.32 × 10-6, and 0.40 × 10-6) approached the threshold of potential carcinogenic risk (1.0 × 10-6). Since these pollutants can continuously accumulate in the soil, the contamination of PCBs, PCNs, and PCDD/Fs in surrounding soil deserves continuous attention.

2,4-Dichlorophenoxyacetic acid (2,4-D) adsorptive removal by algal magnetic activated carbon nanocomposite

In the present study, ferric oxide nanoparticles impregnated with activated carbon from Ulva prolifera biomass (UPAC-Fe₂O₃) were prepared and employed to remove 2,4-Dichlorophenoxyacetic acid (2,4-D) by adsorption. The UPAC-Fe₂O₃ nanocomposite was characterized for its structural and functional properties by a variety of techniques. The nanocomposite had a jagged, irregular surface with pores due to uneven scattering of Fe₂O₃ nanoparticles, whereas elemental analysis portrayed the incidence of carbon, oxygen, and iron. XRD analysis established the crystalline and amorphous planes corresponding to the iron oxide and carbon phase respectively. FT-IR analyzed the functional groups that confirmed the integration of Fe₂O₃ nanoparticles onto nanocomposite surfaces. VSM and XPS studies uncovered the superparamagnetic nature and presence of carbon and Fe₂O_3, respectively, in the UPAC-Fe₂O₃ nanocomposite. While the surface area was 292.51 m²/g, the size and volume of the pores were at 2.61 nm and 0.1906 cm³/g, respectively, indicating the mesoporous nature and suitability of the nanocomposites that could be used as adsorbents. Adsorptive removal of 2,4-D by nanocomposite for variations in process parameters like pH, dosage, agitation speed, adsorption time, and 2,4-D concentration was studied. The adsorption of 2,4-D by UPAC-Fe₂O₃ nanocomposite was monolayer chemisorption owing to Langmuir isotherm behavior along with a pseudo-second-order kinetic model. The maximum adsorption capacity and second order rate constant values were 60.61 mg/g and 0.0405 g/mg min respectively. Thermodynamic analysis revealed the spontaneous and feasible endothermic adsorption process. These findings confirm the suitability of the synthesized UPAC-Fe₂O₃ nanocomposite to be used as an adsorbent for toxic herbicide waste streams.

Dinitroaniline herbicides: a comprehensive review of toxicity and side effects on animal non-target organisms

The widespread use of herbicides has increased concern about the hazards and risks to animals living in terrestrial and aquatic ecosystems. A comprehensive understanding of their effective action at different levels of biological organization is critical for establishing guidelines to protect ecosystems and human health. Dinitroanilines are broad-spectrum pre-emergence herbicides currently used for weed control in the conventional agriculture. They are considered extremely safe agrochemicals because they act specifically on tubulin proteins and inhibit shoot and root growth of plants. However, there is a lack of toxicity information regarding the potential risk of exposure to non-target organisms. The aim of the present review is to focus on side effects of the most commonly used active ingredients, e.g. pendimethalin, oryzalin, trifluralin and benfluralin, on animal non-target cells of invertebrates and vertebrates. Acute toxicity varies from slightly to high in terrestrial and aquatic species (i.e. nematodes, earthworms, snails, insects, crustaceans, fish and mammals) depending on the species-specific ability of tested organisms to adsorb and discharge toxicants. Cytotoxicity, genotoxicity and activation of oxidative stress pathways as well as alterations of physiological, metabolic, morphological, developmental and behavioural traits, reviewed here, indicate that exposure to sublethal concentrations of active ingredients poses a clear hazard to animals and humans. Further research is required to evaluate the molecular mechanisms of action of these herbicides in the animal cell and on biological functions at multiple levels, from organisms to communities, including the effects of commercial formulations.