A qualitative review of the epidemiological literature on the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and health after 2001 is presented. In order to compare the exposure of the general population, bystanders and occupational groups, their urinary levels were also reviewed. In the general population, 2,4-D exposure is at or near the level of detection (LOD). Among individuals with indirect exposure, i.e. bystanders, the urinary 2,4-D levels were also very low except in individuals with opportunity for direct contact with the herbicide. Occupational exposure, where exposure was highest, was positively correlated with behaviors related to the mixing, loading and applying process and use of personal protection. Information from biomonitoring studies increases our understanding of the validity of the exposure estimates used in epidemiology studies. The 2,4-D epidemiology literature after 2001 is broad and includes studies of cancer, reproductive toxicity, genotoxicity, and neurotoxicity. In general, a few publications have reported statistically significant associations. However, most lack precision and the results are not replicated in other independent studies. In the context of biomonitoring, the epidemiology data give no convincing or consistent evidence for any chronic adverse effect of 2,4-D in humans.

In this study, the inheritance of 2,4-D resistance in a multiple herbicide-resistant Palmer amaranth (KCTR) was investigated. Direct and reciprocal crosses were performed using 2,4-D-resistant KCTR and susceptible KSS plants to generate F1 progenies. 2,4-D dose-response assays were conducted to evaluate the response of progenies from each F1 family along with KCTR and KSS plants in controlled environmental growth chambers. Additionally, 2,4-D-resistant male and female plants from each of the F1 families were used in pairwise crosses to generate pseudo-F2 families. Segregation (resistance or susceptibility) of progenies from the F2 families in response to a discriminatory rate of 2,4-D (i.e., 560 g ae ha-1) was evaluated. Dose-response analysis of F1 progenies derived from direct and reciprocal crosses suggested that the 2,4-D resistance in KCTR is a nuclear trait. Chi-square analyses of F2 segregation data implied that 2,4-D resistance in KCTR is controlled by multiple gene(s). Overall, our data suggest that the 2,4-D resistance in KCTR Palmer amaranth is a nuclear inherited trait controlled by multiple genes. Such resistance can spread both via pollen or seed-mediated gene flow. In future, efforts will be directed towards identifying genes mediating 2,4-D resistance in KCTR population.

Exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) has several deleterious effects on the nervous system such as alterations in the concentrations of neurotransmitters in the brain and/or behavioral changes, myelination rate, ganglioside pattern [Bortolozzi, A., Duffard, R., Antonelli, M., Evangelista de Duffard, A.M., 2002. Increased sensitivity in dopamine D(2)-like brain receptors from 2,4-dichlorophenoxyacetic acid (2,4-D)-exposed and amphetamine-challenged rats. Ann. N.Y. Acad. Sci. 965, 314-323; Duffard, R., García, G., Rosso, S., Bortolozzi, A., Madariaga, M., DiPaolo, O., Evangelista de Duffard, A.M., 1996. Central nervous system myelin deficit in rats exposed to 2,4-dichlorophenoxyacetic acid throughout lactation. Neurotoxicol. Teratol. 18, 691-696; Evangelista de Duffard, A.M., Orta, C., Duffard, R., 1990. Behavioral changes in rats fed a diet containing 2,4-dichlorophenoxyacetic butyl ester. Neurotoxicology 11, 563-572; Evangelista de Duffard, A.M., Bortolozzi, A., Duffard, R.O., 1995. Altered behavioral responses in 2,4-dichlorophenoxyacetic acid treated and amphetamine challenged rats. Neurotoxicology 16, 479-488; Munro, I.C., Carlo, G.L., Orr, J.C., Sund, K., Wilson, R.M. Kennepohl, E. Lynch, B., Jablinske, M., Lee, N., 1992. A comprehensive, integrated review and evaluation of the scientific evidence relating to the safety of the herbicide 2,4-D. J. Am. Coll. Toxicol. 11, 559-664; Rosso et al., 2000], and its administration to pregnant and lactating rats adversely affects litter growth and milk quality. Since normal growth of the offspring depends on adequate maternal nursing and care, we evaluated the effect of 2,4-D on rat maternal behavior as well as the dam's monoamine levels in arcuate nucleus (AcN) and serum prolactin (PRL) levels. Wistar dams were exposed to the herbicide through the food from post partum day (PPD) 1 to PPD 7. Dams were fed either with a 2,4-D treated diet (15, 25 or 50mg 2,4-D/kg/daybw) or with a control diet. We observed that maternal nesting behavior was not modified by 2,4-D treatment. However, mother-pup interactions, specially the nursing behavior, were altered. Retrieval, crouching and licking of pups were reduced or suspended after 2,4-D treatment. We also observed an increase in the latency of retrieval and crouching in the dams treated with the herbicide. Dams showed movement along cage peripheries, food consumption during the light phase and high self-grooming. In addition of the deficits observed in maternal behavior parameters, increased catecholamine levels and a drastic decrease in indolamine levels in the AcN of treated dams were determined. Serum PRL levels were also diminished by 62%, 68% and 70% with respect to control dams in the 15, 25 and 50mg 2,4-D/kgbw treated dams, respectively. In conclusion, exposure to 2,4-D during the first post partum days produced changes in maternal behavior, serum prolactin and monoamine levels in the AcN of treated dams.

2,4-Dichlorophenoxyacetic acid (2,4-D) is widely used in agriculture as herbicide/pesticide, plant growth regulator and fruit preservative agent. It progressively accumulates in the environment including surface water, air and soil. It could be detected in human food and urine, which poses great risk to the living organisms. In the present study, we investigated the developmental toxicity of 2,4-D on zebrafish (Danio rerio) embryo. 2,4-D exposure significantly decreased both the survival rate (LC50 = 46.71 mg/L) and hatching rate (IC50 = 46.26 mg/L) of zebrafish embryos. The most common developmental defect in 2,4-D treated embryos was pericardial edema. 2,4-D (25 mg/L) upregulated marker genes of cardiac development (vmhc, amhc, hand2, vegf, and gata1) and downregulated marker genes of oxidative stress (cat and gpx1a). Whole mount in situ hybridization confirmed the vmhc and amhc upregulation by 2,4-D treatment. LC/MS/MS showed that the bioaccumulation of 2,4-D in zebrafish embryos were increased in a time-dependent manner after 25 mg/L of 2,4-D treatment. Taken together, our study investigated the toxic effects of 2,4-D on zebrafish embryonic development and its potential molecular mechanisms, gave evidence for the full understanding of 2,4-D toxicity on living organisms and shed light on its environmental impact.

The objective of this study was to evaluate the potential for non-invasive biomonitoring of 2,4-Dichlorophenoxyacetic acid (2,4-D) in saliva. Using an in vitro rat salivary gland epithelial cell (SGEC) system, a collection of experiments investigating chemical protein binding, temporal and directional transport, as well as competitive transport with para-aminohippuric acid (PAH), a substrate for renal organic anion transporters, was conducted to identify cellular transport parameters required to computationally model salivary transport of 2,4-D. Additionally, a physiological protein gradient was implemented to mimic physiologically relevant concentrations of protein in rat plasma and saliva, and under these conditions the transfer of 2,4-D was markedly slower, driven by increased protein binding (i.e. reduced free 2,4-D species available to cross salivary barrier). The rate of transfer was directly proportional to the amount of unbound 2,4-D and demonstrated no indication of active transport. An in vivo assessment of 2,4-D exposure in rats revealed non-linear protein binding in plasma, indicating saturated protein binding and increased levels of unbound 2,4-D species at higher doses. A strong correlation between 2,4-D concentrations in saliva and unbound 2,4-D in plasma was observed (Pearson correlation coefficient = 0.95). Saliva:plasma 2,4-D ratios measured in vivo (0.0079) were consistent within the linear protein binding range and expected 2,4-D levels from occupational exposures but were significantly different than ratios measured in vitro (physiological conditions) (0.034), possibly due to 2,4-D concentrations in saliva not being at equilibrium with 2,4-D concentrations in blood, as well as physiological features absent in in vitro settings (e.g. blood flow). We demonstrated that 2,4-D is consistently transported into saliva using both in vitro and in vivo models, making 2,4-D a potential candidate for human non-invasive salivary biomonitoring. Further work is needed to understand whether current sensor limits of detection are sufficient to measure occupationally relevant exposures.

The development of low-cost and eco-friendly materials for the removal of pollutants from water is one of the main modern challenges. For this purpose, molecularly imprinted polymers were prepared under optimized conditions starting from chitosan (CS), chemically or ionically modified with glycidyl methacrylate (GMA) or itaconic acid (ITA), respectively. 2,4-Dichlorophenoxyacetic acid (2,4-D) was used as a template, obtaining the CS_GMA and CS_ITA series. The influence of the template concentration on the MIPs' (molecularly imprinted polymers) morphology, thermal behaviour and swelling ability, as well as on the 2,4-D removal capacity, were analyzed. The amount of the template used for the imprinting, together with the different permeability of the matrices, were the key factors driving the analyte uptake process. Despite the good performance shown by the non-imprinted CS_GMA sample, the best results were obtained when CS_GMA was imprinted with the highest amount (5%) of template (CS_GMA_5). This system was also more efficient when consecutive adsorption experiments were carried out. In addition, CS_GMA_5 had a desorption efficiency of 90-100% when a low pesticide concentration was used. These findings suggest that the presence of imprinted cavities could be useful in improving the performance of sorbent materials making CS_GMA_5 a possible candidate for 2,4-D removal.

We estimated 2,4-dichlorophenoxyacetic acid (2,4-D) exposure and systemic dose in farm family members following an application of 2,4-D on their farm.

This research investigated persulfate electrosynthesis using a boron-doped diamond anode and a chemical reaction of persulfate in its activated form with an herbicide, 2,4-Dichlorophenoxyacetic acid (2,4-D). The first part of this research is dedicated to the influence of the applied current density on the electrosynthesis of persulfate. The first part shows that for a 2 M sulfuric acid, the current efficiency reached 96% for 5 mA/cm2 and dropped to 52% for a higher current density (100 mA cm-2). This fall cannot be explained by mass transfer limitations: an increase in temperature (from 9 to 30 °C) during electrolysis leads to the decomposition of 23% of the persulfate. The second part of this research shows that a quasi-complete degradation of the target herbicide can be reached under controlled operating conditions: (i) a high ratio of initial concentrations [Persulfate]/[2,4-D], (ii) a minimum temperature of 60 °C that produces sulfate radicals by heat decomposition of persulfate, and (iii) a sufficient contact time between reactants is required under dynamic conditions.

Three different fungi were tested for their ability to degrade 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid and for the role of laccases and cytochromes P450-type in this process. We studied a white-rot fungus Rigidoporus sp. FMD21, which has a high laccase activity, for its efficiency to degrade these herbicides. A positive correlation was found between its laccase activity and the corresponding herbicide degradation rate. Even more, the doubling of the enzyme activity in this phase corresponded with a doubling of the herbicide degradation rate. It is, therefore, tempting to speculate that laccase is the most dominant enzyme in the degradation of 2,4-D and 2,4,5-T under these conditions. In addition, it was shown that Rigidoporus sp. FMD21 partly relies on cytochromes P450-type for the breakdown of the herbicides as well. Two filamentous fungi were isolated from soil contaminated with herbicides and dioxins located at Bien Hoa airbase. They belong to genera Fusarium and Verticillium of the phylum Ascomycota as judged by their 18S rRNA gene sequences. Both isolated fungi were able to degrade the herbicides but with different rates. Their laccase activity, however, was very low and did not correlate with the rate of breakdown of the herbicides. These data indicate that the white-rot fungus most likely synthesizes laccase and cytochromes P450-type for the breakdown of the herbicides, while the types of enzyme used for the breakdown of the herbicides by the two Ascomycota remain unclear.

The auxin-like compound 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely used as a plant growth regulator in cucumber fruit production; however, its influence on fruit development and metabolism has not been evaluated. In this study, the phenotype of cucumber fruits in both 2,4-D treatment and non-treatment control groups were recorded, and the metabolome of different segments of cucumber fruit at various sampling time points were profiled by a standardized non-targeted metabolomics method based on UPLC-qTOF-MS. The application of 2,4-D increased the early growth rate of the fruit length but had no significant effect on the final fruit length, and produced cucumber fruits with fresh flowers at the top. The 2,4-D treatment also affected the cucumber fruit metabolome, causing significant changes in the stylar end at 4 days after flowering (DAF). The significantly changed metabolites were mainly involved in methionine metabolism, the citric acid cycle and flavonoid metabolism pathways. At the harvest stage, 2,4⁻D treatment significantly decreased the levels of flavonoids and cinnamic acid derivatives while increased the levels of some of the amino acids. In summary, exogenous application of 2,4-D can greatly alter the phenotype and metabolism of cucumber fruit. These findings will assist in exploring the mechanisms of how 2,4-D treatment changes the fruit phenotype and evaluating the influence of 2,4-D treatment on the nutritional qualities of cucumber fruit.

The herbicide dichlorophenoxyacetic acid (2,4-D) is one of the most widely used crop spraying products in the world. Some pesticides induce the degranulation of mast cells and increase allergic responses. This is the first study to evaluate the damage to the oral mucosa after an experimental simulation of environmental inhalation exposure to the 2,4-D herbicide. The aim of this study was evaluate the possible oral damage caused by acute inhalation exposure to the herbicide 2,4-D.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide of the chlorophenoxy class and the second most widely used herbicide applied to several different crops worldwide. Environmental factors, especially those related to diet, strongly affect the risk of developing cancer of the gastrointestinal tract. There is currently no evidence to determine whether there is an association between 2,4-D exposure and gastrointestinal disorders. We evaluated the histological effect of chronic oral and inhalation exposure to 2,4-D on the digestive tract of rats. Eighty male adult albino Wistar rats were divided into 8 groups (n=10): two control groups, one for inhalation and one for oral exposure, and 6 groups exposed orally or by inhalation at three different concentrations of 2,4-D [3.71×10-3 grams of active ingredient per hectare (gai/ha), 6.19×10-3 gai/ha, and 9.28×10-3 gai/ha]. The animals were exposed for 6 months. The esophagus, stomach, and intestine were collected for histopathological analysis. Animals exposed to 2,4-D had hyperkeratosis of the esophagus, regardless of the exposure route. All animals exposed to a higher concentration of 2,4-D orally presented mild dysplasia of the large intestine. In the small intestine, most animals exposed to moderate and high concentrations of 2,4-D had mild dysplasia. No gastric changes were observed in any of the groups studied. Chronic exposure to 2,4-D, especially at moderate and high concentrations, regardless of the exposure route, caused reactive damage to the esophagus (hyperkeratosis) and dysplastic changes to the intestine.

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most applicable herbicides in the world. Therefore, its residue in aquatic environment threatens the human health and ecosystems. In this study, Fe2O3 (hematite) nanoparticles (HNPs) were synthesized, and the characteristics of the obtained HNPs were determined using X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) technique, and particle size analyzer (PSA). The catalytic activity of HNPs was evaluated for the activation of peroxymonosulfate (PMS) for the degradation of 2,4-D. The effects of the operating parameters were studied for the PMS/HNPs system. The results showed that the acidic condition provided higher efficiency, while overdosing of PMS had a scavenging effect. The PMS/HNPs showed high efficiency in comparison with the homogeneous forms of iron (Fe2+ and Fe3+). Reusability of HNPs was studied in five consequent usages. The presence of the anions (chloride, nitrate, and hydrogen phosphate) reduced the 2,4-D degradation. Moreover, the catalytic activity of HNPs was also investigated in the presence of other oxidants. UV irradiation increased the function of PMS/HNPs and its mechanism was described. The order of 2,4-D removal for the oxidants was PMS > persulfate > H2O2 > percarbonate. A total of 29.7% of 2,4-D chlorine content was released during the destruction of 2,4-D. The quenching study showed that sulfate radical was the major agent in the degradation of 2,4-D.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a chlorophenoxy herbicide used worldwide. We describe a high-performance liquid chromatography (HPLC) method with UV detection for the determination of 2,4-D in female and male rat serum. This allows to observe the change of serum 2,4-D concentration in rats with time and its pharmacokinetics characteristics with a simple, rapid, optimized and validated method. The serum samples are pretreated and introduced into the HPLC system. The analytes are separated in a XDB-C18 column with a mobile phase of acetonitrile (solvent A) and 0.02 M ammonium acetate (containing 0.1% formic acid) (solvent B) using a gradient elution at a flow rate of 1.0 mL/min. The wavelength for UV detection was set at 230 nm. Calibration curve for 2,4-D was constructed over a range of 0.1-400 mg/L. The method was successfully applied to study the pharmacokinetics of 2,4-D in rats in this study. After oral administration of 300 mg/kg and 60 mg/kg 2,4-D, the mean Cmax values were 601.9 and 218.4 mg/L, the AUC0→∞ values were 23,722 and 4,127 mg×h/L and the clearance (Cl) were 1.10 and 0.02 L/(h×kg), respectively. The developed method was found to be specific, precise, reproducible and rapid.

2,4-Dichlorophenoxyacetic acid (2,4-D) is the third most applied pesticide in Brazil to control broadleaf weeds in crop cultivation and pastures. Due to 2,4-D's high mobility and long half-life under anoxic conditions, this herbicide has high probability for groundwater contamination. Bioremediation is an attractive solution for 2,4-D contaminated anoxic environments, but there is limited understanding of anaerobic 2,4-D biodegradation. In this study, methanogenic enrichment cultures were obtained from Amazonian top soil (0-40 cm) and deep soil (50 -80 cm below ground) that biotransform 2,4-D (5 µM) to 4-chlorophenol and phenol. When these cultures were transferred (10% v/v) to fresh medium containing 40 µM or 160 µM 2,4-D, the rate of 2,4-D degradation decreased, and biotransformation did not proceed beyond 4-chlorophenol and 2,4-dichlorophenol in the top and deep soil cultures, respectively. 16S rRNA gene sequencing and qPCR of a selection of microbes revealed no significant enrichment of known organohalide-respiring bacteria. Furthermore, a member of the genus Cryptanaerobacter was identified as possibly responsible for phenol conversion to benzoate in the top soil inoculated culture. Overall, these results demonstrate the effect of 2,4-D concentration on biodegradation and microbial community composition, which are both important factors when developing pesticide bioremediation technologies.

Two series of Fe2O3/TiO2 samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe2O3/TiO2 for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe2O3/TiO2 nanocomposites prepared by impregnation showed lower activity than the unmodified TiO2, mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe2O3/TiO2 nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO2. Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe2O3(0.5)/TiO2. The improved activity of TiO2 after photodeposition of Fe2O3 was contributed to the formation of a heterojunction between the Fe2O3 and TiO2 nanoparticles that improved charge transfer and suppressed electron-hole recombination. A further investigation on the role of the active species on Fe2O3/TiO2 confirmed that the crucial active species were both holes and superoxide radicals. The Fe2O3(0.5)/TiO2 sample also showed good stability and reusability, suggesting its potential for water purification applications.

Pesticide residues in food and environment along with airborne contaminants such as endotoxins pose health risk. Although herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) has been associated with increased risk of lung cancers such as small cell lung cancer (SCLC) among agricultural workers, there are no data on the SCLC signaling pathway upon 2,4-D exposure without LPS or in combination with endotoxin.

2,4-Dichlorophenoxyacetic acid (2,4-D) was assessed for systemic toxicity, reproductive toxicity, developmental neurotoxicity (DNT), developmental immunotoxicity (DIT), and endocrine toxicity. CD rats (27/sex/dose) were exposed to 0, 100, 300, 600 (female), or 800 (male) ppm 2,4-D in diet. Nonlinear toxicokinetic behavior was shown at high doses; the renal clearance saturation threshold for 2,4-D was exceeded markedly in females and slightly exceeded in males. Exposure was 4 weeks premating, 7 weeks postmating for P1 males and through lactation for P1 females. F1 offspring were examined for survival and development, and at weaning, pups were divided in cohorts, by sex and dose, and by systemic toxicity (10), DNT (10), DIT (20), and reproductive toxicity (≥ 23). Remaining weanlings were evaluated for systemic toxicity and neuropathology (10-12). Body weight decreased during lactation in high-dose P1 females and in F1 pups. Kidney was the primary target organ, with slight degeneration of proximal convoluted tubules observed in high-dose P1 males and in high-dose F1 males and females. A slight intergenerational difference in kidney toxicity was attributed to increased intake of 2,4-D in F1 offspring. Decreased weanling testes weights and delayed preputial separation in F1 males were attributed to decreased body weights. Endocrine-related effects were limited to slight thyroid hormone changes and adaptive histopathology in high-dose GD 17 dams seen only at a nonlinear toxicokinetic dose. 2,4-D did not cause reproductive toxicity, DNT, or DIT. The "No Observed Adverse Effect Level" for systemic toxicity was 300 ppm in both males (16.6 mg/kg/day) and females (20.6 mg/kg/day), which is approximately 6700- to 93 000-fold higher than that reported for 2,4-D exposures in human biomonitoring studies.

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.

The effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on brain monoamines and the serum level of hormones involved in milk synthesis and on the milk ejection reflex in rats were evaluated. Dams were treated with 2.5, 5, 15, 25, 50 or 70mg 2,4-D/kg bw according to two experimental designs: (a) through food from post partum day 1 (PPD 1) to PPD 16 and the respective control groups or (b) an unique i.p. injection on PPD 11. To measure milk ejection, the litter was separated from the mother at the 11th day of lactation during 8h, returned to their mothers and allowed to suckle for a period of 15min. The procedure was repeated on 3 consecutive days until the end of treatment. The change in litter weight during the suckling period was taken as a measure of the amount of milk ejected during this period. The dams' serum prolactin (PRL), oxytocin (OT) and growth hormone levels were determined by radioimmunoassay. Both treatment regimens produced a dose-dependent decrease in the amount of milk ejected and circulating PRL and OT secreted in response to the suckling stimulus. Administration of OT before returning the pups restored the milk ejection, indicating no impairment in the capacity of the mammary gland to produce and secrete milk. In addition, dopamine levels were increased by the 2,4-D treatments in arcuate nucleus (ArN) and anterior lobe of pituitary gland (AL), while serotonin level was drastically decreased in ArN. 2,4-D treatment increased both calcium-dependent and calcium-independent nitric oxide synthase (NOS) activities in ArN. These results suggest that 2,4-D inhibits the suckling-induced hormone release, milk transfer to the litter at the central level, through a stimulation of hypothalamic NOS and dopamine and by an inhibition of hypothalamic serotonin transmission.