A novel green molecularly imprinted polymers synthesized in an aqueous medium as S-metolachlor sensitive materials.

A new molecularly imprinted polymer (MIP) sensitive and selective for S-metolachlor herbicide was synthesized by bulk polymerization with the use of N-isopropylacrylamide, acrylamide, and acrylic acid as functional monomers, and N,N'- methylenebis(acrylamide) as a cross-linker. A novel method for obtaining MIP toward S-metolachlor in an aqueous medium and at room temperature, according to the principles of green chemistry, has been discovered, in comparison to synthesis methods at high temperatures and using organic solvents. Under selected experimental conditions, the batch mode type of sorption was carried out efficiently, with S-metolachlor absorption of 2.4 mg per 1 g of MIP and 0.5 mg per 1 g of NIP. The selectivity of the sorbent towards other herbicides and pesticides was also tested, obtaining an ability to recognize S-metolachlor molecules 3.2 times better than atrazine, 6 times better than glyphosate, and 6.2 times better than fenoxaprop-P-ethyl. The FT-IR and SEM analyses were performed to characterize the structure of the synthesized polymers.

Antibiotics alter the metabolic profile of metolachlor in soil-plant system by disturbing the detoxifying process and oxidative stress.

Antibiotics are widely detected in farmland, which may influence the environmental behavior and risks of the coexisting pesticide. In this work, the effects of antibiotics on metolachlor transformation in soil-pea and the risk of metolachlor to earthworm were assessed, and the mechanism was explored in view of detoxifying process and oxidative stress. Antibiotics affected not the degradation rate but the metabolic profile of metolachlor. In soil, the content of metabolites oxaloacetic acid (OA) and ethane sulfonic acid (ESA) was decreased and dechlorometolachlor (DCL) was increased by antibiotics. In pea, the accumulation of metolachlor, DCL and ESA was decreased, while OA was increased by antibiotics. The changed transformation of metolachlor affected the risk to earthworm according to risk quote assessment. In further research, it was found that cytochrome P450 (CYP450) enzyme was reduced by 12.3% - 30.4% in soil and 12.4% - 23.6% in pea, which might due to excessive ROS accumulation induced by antibiotics, thus affecting the transformation and metabolite profile of metolachlor in soil-plant system.

In vitro and in silico analyses reveal the toxicity of metolachlor to grass carp hepatocytes and the antagonism of melatonin.

Due to the widespread use of metolachlor (MET), the accumulation of MET and its metabolites in the environment has brought serious health problems to aquatic organisms. At present, the toxicity of MET on the physiological metabolism of aquatic animals mainly focused on the role of enzymes. There is still a lack of research on the molecular mechanisms of MET hepatotoxicity, especially on antagonizing MET toxicity. Therefore, this study focuses on grass carp hepatocytes (L8824 cells) closely related to toxin accumulation. By establishing a MET exposed L8824 cells model, it is determined that MET exposure induces pyrolytic inflammation of L8824 cells. Subsequent mechanistic studies found that MET exposure induces pyroptosis in L8824 cells through mitochondrial dysfunction, and siCaspase-1 inhibits the MET induced ROS production, suggesting a regulation of ROS-NLRP3- Caspase-1 pyroptotic inflammation cycling center in MET induced injury to L8824 cells. Molecular docking revealed a strong binding energy between melatonin (MT) and Caspase-1. Finally, a model of L8824 cells with MT intervention in MET exposure was established. MT can antagonize the pyroptosis induced by MET exposure in L8824 cells by targeting Caspase-1, thereby restoring mitochondrial function and inhibiting the ROS-pyroptosis cycle. This study discovered targets and mechanisms of MT regulating pyroptosis in MET exposed-L8824 cells, and the results are helpful to provide new targets for the design of MET antidotes.

Effects of a S-metolachlor based herbicide on two plant models: Zea mays L. and Lactuca sativa L.

Corn is the second most cultivated crop in Brazil, the number-one country in pesticide consumption. Chemical control of weeds is performed using herbicides such as S-metolachlor with pre- and post-emergence action and thus the toxicity of herbicides constitutes a matter of great concern. The present investigation aimed to examine the effects of an S-metolachlor-based herbicide on Lactuca sativa L. (lettuce) and Zea mays L. (maize) utilizing various bioassays. The test solutions were prepared from commercial products containing the active ingredient. Seeds from the plant models were exposed in petri dishes and maintained under biochemical oxygen demand (BOD) at 24°C. Distilled water was negative and aluminium positive control. Macroscopic analyses (germination and growth) were conducted for both plant species, and microscopic analysis (cell cycle and chromosomal alterations) were performed for L. sativa root tip cells. Detrimental interference of S-metolachlor-based herbicide was noted with lettuce for all parameters tested reducing plant germination by over 50% and the germination speed by over 45% and showing a significant decrease in mitotic index, from 16.25% to 9,28% even on the lowest concentration tested. In maize, there was no significant interference in plant germination; however, speed of germination was significantly hampered, reaching a 51.22% reduction for the highest concentration tested. Data demonstrated that the herbicide was toxic as evidenced by its phyto- and cytotoxicity in L. sativa L. and Z. mays L.

The role of ponds in pesticide dissipation at the catchment scale: The case of the Save agricultural catchment (Southwestern France).

Pesticides are a major source of pollution for ecosystems. In agricultural catchments, ponds serve as buffer areas for pesticide transfers and biogeochemical hotspots for pesticide dissipation. Some studies have highlighted the specific impact of ponds on the dynamics of pesticides, but knowledge of their cumulative effect at the watershed scale is scarce. Hence, using a modelling approach, we assessed the cumulative role of ponds in pesticide transfer in an agricultural basin (Southwest of France, 1110 km2). The Soil and Water Assessment Tool (SWAT) model was used to model the Save basin, including 197 ponds selected with a Multi-Criteria Decision Aiding Model based on their pesticide interception capacities. The daily discharge, the suspended sediment loads and two herbicide loads (i.e. S-metolachlor and aclonifen) in dissolved and particulate phases were accurately simulated from January 2002 to July 2014 at a daily time step. The presence of ponds resulted in a yearly mean reduction at the watershed outlet of respectively 61 % and 42 % of aclonifen and S-metolachlor fluxes compared to the simulations in the absence of ponds. Sediment-related processes were the most efficient for pesticide dissipation, leading to a mean dissipation efficiency by ponds of 51.0 % for aclonifen and 34.4 % for S-metolachlor. This study provides a first quantification of the cumulative role of ponds in pesticide transfer at the catchment scale in an intensive agricultural catchment.

Enantioselectivity regulation of antibody against chiral herbicide metolachlor based on interaction at chiral center.

Enantioselective antibodies have emerged as great potential biomaterials in the fields of immunoassays and chiral separation. However, cross-reactivity of antibodies to the distomer may severely restrict the application. Comprehending the interaction mechanism between antibodies and enantiomers could be beneficial to produce superior enantioselective antibodies. In this study, a pair of recombinant antibodies (RAbs) against metolachlor enantiomers at chiral carbon (αSS-MET and αSR-MET) were generated and characterized. The αSS-MET-RAb and αSR-MET-RAb showed comparable sensitivity and specificity to the parental monoclonal antibodies by icELISA, with IC50 values of 3.45 and 223.77 ng/mL, respectively. Moreover, the complex structures of RAbs and corresponding eutomer were constructed and analyzed, and site-specific mutagenesis was utilized to verify the reliability of the enantioselective mechanism elucidated. It demonstrated that the strength of the interaction between the chiral center region of eutomer and the antibody was the key factor for the enantioselectivity of antibody. Increasing this interaction could limit the conformational adjustment of the distomer in a specific chiral recognition cavity, thus decreasing the affinity of the antibody to the distomer. This work provided the in-depth analysis of enantioselective mechanism for two RAbs and paved the way to regulate antibody enantioselective performance for immunoassays of chiral compounds.

Central Chirality and Axial Chirality Recognition of the Enantioselective Antibodies to Herbicide Metolachlor.

Enantioselective antibodies have emerged as efficient tools in the field of chiral chemical detection and separation. However, it is complicated to obtain a highly stereoselective antibody due to the unclear recognition mechanism. In this study, the hapten of metolachlor was synthesized and enantio-separated. The absolute configuration of the four haptens obtained was identified by the computed and experimental electronic circular dichroism comparison. Five polyclonal antibodies against the Rac-metolachlor and its enantiomers were generated by immunization. The cross-activity of all the 5 antibodies with 44 structural analogues, including metolachlor enantiomers, was tested. It demonstrated that antibodies have higher specificity to recognize central chirality than axial chirality. Especially, αRR-MET-Ab exhibited excellent specificity and stereoselectivity. Accordingly, 3D-QSAR models were constructed and revealed that paired stereoisomers exhibited opposite interactions with the antibodies. It is the first time that the antibodies against four stereoisomers were prepared and analyzed, which will be conducive to the rational design of the stereoselective antibodies.

The Cocktail Effects on the Acute Cytotoxicity of Pesticides and Pharmaceuticals Frequently Detected in the Environment.

Xenobiotics never appear as single, isolated substances in the environment but instead as multi-component mixtures. However, our understanding of the ecotoxicology of mixtures is far from sufficient. In this study, three active pharmaceutical ingredients (carbamazepine, diclofenac, and ibuprofen) and three pesticides (S-metolachlor, terbuthylazine, and tebuconazole) from the most frequently detected emerging micropollutants were examined for their acute cytotoxicity, both individually and in combination, by bioluminescence inhibition in Aliivibrio fischeri (NRRL B-11177). Synergy, additive effects, and antagonism on cytotoxicity were determined using the combination index (CI) method. Additionally, PERMANOVA was performed to reveal the roles of these chemicals in binary, ternary, quaternary, quinary, and senary mixtures influencing the joint effects. Statistical analysis revealed a synergistic effect of diclofenac and carbamazepine, both individually and in combination within the mixtures. Diclofenac also exhibited synergy with S-metolachlor and when mixed with ibuprofen and S-metolachlor. S-metolachlor, whether alone or paired with ibuprofen or diclofenac, increased the toxicity at lower effective concentrations in the mixtures. Non-toxic terbuthylazine showed great toxicity-enhancing ability, especially at low concentrations. Several combinations displayed synergistic effects at environmentally relevant concentrations. The application of PERMANOVA was proven to be unique and successful in determining the roles of compounds in synergistic, additive, and antagonistic effects in mixtures at different effective concentrations.

Adsorption characteristics of S-Metolachlor onto the sawdust biochar derived from Acacia auriculiformis.

The adsorption mechanism of S-Metolachlor in an aqueous solution by sawdust biochar derived from Acacia auriculiformis (SAB) was studied. SAB was manufactured at 500 °C for 4 h under oxygen-limited conditions and characterized for SEM, EDS, pHpzc, BET, and FTIR. The adsorption kinetics, isotherm, and diffusion studies of S-Metolachlor and SAB were further explored. Moreover, the effects of the solution pH were examined on the adsorption of S-Metolachlor by SAB. The BET analysis of SAB was achieved at 106.74 m2.g-1 and the solution pH did not significantly influence the S-Metolachlor adsorption. The adsorption data were fitted into a Langmuir isotherm and the PSO model. The film diffusion coefficient Df (4.93 × 10-11 to 8.17 × 10-11 m2.s-1) and the particle diffusion coefficient Dp (1.68 × 10-11 to 2.65 × 10-11 m2.s-1) were determined and the rate-limiting step of S-Metolachlor adsorption and SAB was governed by liquid film diffusion. The S-Metolachlor adsorption process onto SAB was controlled by multiple mechanisms, including pore filling, H-bonding, hydrophobic interaction, and π-π EDA interactions. H-bonding is the main interaction for the adsorption of S-Metolachlor and SAB. Conclusively, the study illustrates that biochar produced from Acacia auriculiformis sawdust possessed effective adsorption properties for S-Metolachlor herbicide.

Effects of atrazine and S-metolachlor on stream periphyton taxonomic and fatty acid compositions.

Extensive pesticide use for agriculture can diffusely pollute aquatic ecosystems through leaching and runoff events and has the potential to negatively affect non-target organisms. Atrazine and S-metolachlor are two widely used herbicides often detected in high concentrations in rivers that drain nearby agricultural lands. Previous studies focused on concentration-response exposure of algal monospecific cultures, over a short exposure period, with classical descriptors such as cell density, mortality or photosynthetic efficiency as response variables. In this study, we exposed algal biofilms (periphyton) to a concentration gradient of atrazine and S-metolachlor for 14 days. We focused on fatty acid composition as the main concentration-response descriptor, and we also measured chlorophyll a fluorescence. Results showed that atrazine increased cyanobacteria and diatom chlorophyll a fluorescence. Both herbicides caused dissimilarities in fatty acid profiles between control and high exposure concentrations, but S-metolachlor had a stronger effect than atrazine on the observed increase or reduction in saturated fatty acids (SFAs) and very long-chain fatty acids (VLCFAs), respectively. Our study demonstrates that two commonly used herbicides, atrazine and S-metolachlor, can negatively affect the taxonomic composition and fatty acid profiles of stream periphyton, thereby altering the nutritional quality of this resource for primary consumers.

Evaluating binding and interaction of selected pesticides with serum albumin proteins by Raman, 1H NMR, mass spectrometry and molecular dynamics simulation.

Addressing the acute pesticide poisoning and toxicity to humans, is a global challenge of top priority. Serum albumin is the most abundant plasma protein, capable of binding with herbicide and pesticide residues. This study reports multifaceted approaches for in-depth and robust investigation of the molecular interactions of selected pesticides, including propanil (PPL), bromoxynil (BXL), metolachlor (MLR) and glyphosate (GPE) with bovine serum albumin (BSA) proteins using experimental (Raman and FTIR spectroscopy, native mass spectrometry and high field 1H NMR), molecular dynamics (MD) simulation and principal component analysis (PCA). The binding of pesticides with BSA resulted in BSA amide I and amide II Raman spectral shifts. PCA of Raman spectra of serum-pesticide complexes showed the grouping of pesticides on the score plot based on the similarities and differences in pesticides' chemical structures. Native mass spectrometry results revealed strong adduct formation of the pesticides with the protein. The observed changes in chemical shifts, peak broadening or peak disappearance of characteristic proton signals of the pesticides, indicated altered chemical environments due to binding BSA-pesticides interactions. The results of MD simulation conducted for over 500 ns revealed strong pesticides interaction with LEU197, LEU218, LEU237, TRP213, SER286 and ILE289 residues to the site I of BSA. Free energy landscapes provided insights into the conformational changes in BSA on the binding of pesticides. Overall, the experimental and computational results are in consonant and indicate the binding of pesticides into the site I and site II (sub-domain IIA) of the BSA via hydrogen bonding, non-covalent and hydrophobic interactions.Communicated by Ramaswamy H. Sarma.

Photodegradation kinetics and halogens release of the emerging concern pollutants dexamethasone and S-metolachlor on TiO2/rGO composites.

This work studies the photocatalytic degradation of solutions containing 0.11 mM of a glucocorticoid (dexamethasone, DEX) and 0.11 mM of an herbicide (S-metolachlor, MTLC), organohalogenated compounds containing fluorine and chlorine atoms in their molecules, respectively. To treat 1 L volume, a mass of 0.5 g of TiO2/rGO composite in suspension has been used as photocatalyst, irradiated with UV-A LEDs with 200 W m-2 of irradiance. MTLC is partially adsorbed on the surface of the catalyst, while DEX is not adsorbed, showing different degradation kinetics. The halogen ions released into the solution from the breakage of the parent molecules, F- and Cl- respectively, were analysed. In the case of MTLC, the released Cl- followed two different kinetic trends, being faster, and with a rate that matched the rate of MTLC disappearance, the part corresponding to non-adsorbed MTLC. In the experiments with DEX solutions a different behaviour was observed; the released F- in the photocatalytic degradation was partially adsorbed on the catalyst surface, but the adsorption capacity decreased with the use of the photocatalyst in consecutive cycles until the solubilised F- matched the degraded concentration of DEX. Furthermore, the mass balance between the degraded contaminant and the solubilised halogen anion, for both contaminants, allowed to conclude the absence of halogenated intermediates under the final operating conditions, that is a remarkable outcome in water remediation processes.

Integrating transcriptome and physiological analyses to elucidate the molecular responses of sorghum to fluxofenim and metolachlor herbicide.

The extensive use of herbicides has raised concerns about crop damage, necessitating the development of effective herbicide safeners. Fluxofenim has emerged as a promising herbicide safener; however, it's underlying mechanism remains unclear. Here, we screened two inbred lines 407B and HYZ to investigate the detoxication of fluxofenim in mitigating metolachlor damage in sorghum. Metolachlor inhibited seedling growth in both 407B and HYZ, while, fluxofenim could significantly restore the growth of 407B, but not effectively complement the growth of HYZ. Fluxofenim significantly increased the activities of glutathione-S-transferase (GST) to decrease metolachlor residue in 407B, but not in HYZ. This implys that fluxofenim may reduce metolachlor toxicity by regulating its metabolism. Furthermore, metolachlor suppressed AUX-related and JA-related genes expression, while up-regulated the expression of SA-related genes. Fluxofenim also restored the expression of AUX-related and JA-related genes inhibited by metolachlor and further increased expression of SA-related genes. Moreover, we noted a significant increase in the content of trans-zeatin O-glucoside (tZOG) and Gibberellin1 (GA1) after the fluxofenim treatment. In conclusion, fluxofenim may reduce the injury of herbicide by affecting herbicide metabolism and regulating hormone signaling pathway.

Adaptation of the metolachlor-degrading fungus Trichoderma harzianum to the simultaneous presence of low-density polyethylene (LDPE) microplastics.

Although it is known that microplastics (MPs) in soils cause a threat to this complex environment, the actual effects of MPs on soil microorganisms and their catabolic activities, particularly with the biodegradation of herbicides, remain unclear. Hence, the objective of this study was to investigate the effects of a simultaneous presence of metolachlor and low-density polyethylene (LDPE) microplastics on growth inhibition and adaptive responses of Trichoderma harzianum in soil microcosms. Using ergosterol content as an indicator of fungal biomass, it was observed that MPs alone had a marginal inhibitory effect on the growth of the fungus, whereas MET exhibited a dose-dependent inhibitory effect on T. harzianum. However, the presence of MPs did not influence the fungal transforming activity toward the herbicide. Conversely, analysis of lipid profiles in the presence of MPs and herbicides revealed a reduction in the overall fluidity of phospholipid fatty acids, primarily attributed to an increase in lysophospholipids. The activities of six extracellular enzymes in the soil, measured using methylumbelliferone-linked substrates, were significantly enhanced in the presence of MET. These findings contribute to a broader understanding of the alterations in fungal activity in soil resulting from the influence of MPs and MET.

Evaluation of confirmatory data following the Article 12 MRL review for S-metolachlor.

The applicant Syngenta Crop Protection AG submitted a request to the competent national authority in Germany to evaluate the confirmatory data that were identified for S-metolachlor in the framework of the maximum residue level (MRL) review under Article 12 of Regulation (EC) No 396/2005 as not available. To address the data gaps, a new freezer storage stability study for S-metolachlor in commodities with high acid content was submitted. However, the data gap on storage stability was considered only partially addressed for strawberries because, in the absence of information on the storage time interval of the samples of the residue trials performed on strawberries, no conclusion on the validity of these trials could be drawn. The data gap on the lack of trials to support the good agricultural practice (GAP) on pineapples was not addressed. Consequently, the existing tentative MRLs for strawberries and pineapple cannot be confirmed and EFSA recommends lowering these MRLs to the enforcement limit of quantification (LOQ). Since a new lower LOQ for enforcement in high acid content commodities of 0.01 mg/kg has been validated, it is proposed to change the existing MRL value from 0.05* to 0.01* mg/kg for these two commodities.

Palmelloid-like phenotype in the alga Raphidocelis subcapitata exposed to pollutants: A generalized adaptive strategy to stress or a specific cellular response?

This work focuses on the formation of palmelloid-like phenotype in the freshwater alga Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata and Selenastrum capricornutum), when exposed to adverse conditions generated by the presence of organic [the antibiotic erythromycin (ERY) and the herbicide metolachlor (MET)] or inorganic [the heavy metals, cadmium (Cd) and zinc (Zn)] pollutants, at environmentally relevant concentrations. This alga in absence of stress or when exposed to ERY or Zn, up to 200 µg/L, essentially showed a single-nucleus state, although algal growth was reduced or stopped. R. subcapitata "switched" to a multinucleated state (palmelloid-like morphology) and accumulated energy-reserve compounds (neutral lipids) when stressed by 100-200 µg/L MET or 200 µg/L Cd; at these concentrations of pollutants, growth was arrested, however, the majority of the algal population (≥83 %) was alive. The formation of palmelloid-like phenotype, at sub-lethal concentrations of pollutants, was dependent on the pollutant, its concentration and exposure time. The multinucleated structure is a transitory phenotype since R. subcapitata population was able to revert to a single-nucleus state, with normal cell size, within 24-96 h (depending on the impact of the toxic in the alga), after being transferred to fresh OECD medium, without pollutants. The obtained results indicate that the formation of a palmelloid-like phenotype in R. subcapitata is dependent on the mode of action of toxics and their concentration, not constituting a generalized defense mechanism against stress. The observations here shown contribute to understanding the different strategies used by the unicellular alga R. subcapitata to cope with severe stress imposed by organic and inorganic pollutants.

Effects of the Herbicide Metolachlor and Pond Drying on Growth and Development of Wood Frog Tadpoles (Lithobates sylvaticus).

Pesticides and climate change are both thought to contribute to the global amphibian decline, yet their combined effects are still poorly understood. Metolachlor is a widespread herbicide applied across North America, but little is known about its effects on amphibians. We used a replicated mesocosm experimental design with different levels of drying (i.e., no drying and medium and rapid drying) and metolachlor concentrations (0, 0.8, 8, and 80 µg/L) to assess their respective and combined effects on wood frog (Lithobates sylvaticus) larvae throughout metamorphosis. Metolachlor had no significant effect on survival and development of tadpoles. However, metolachlor significantly interacted with drying levels to reduce the growth of tadpoles, which was mainly due to a difference detected among metolachlor concentrations under the rapid drying treatment. Drying also directly reduced growth and body mass at metamorphosis. Our results suggest that environmental stressors, such as drying, should be considered in toxicological experiments to provide relevant exposure conditions to pesticides for ephemeral pond species in the context of global climate change. Environ Toxicol Chem 2023;42:1772-1781. © 2023 SETAC.

Exploratory Analysis on Herbicide Metabolism and Very-Long-Chain Fatty Acid Production in Metolachlor-Resistant Palmer Amaranth (Amaranthus palmeri S. Wats.).

A Palmer amaranth (Amaranthus palmeri S. Wats.) biotype resistant to S-metolachlor was confirmed from crop fields in Arkansas, USA. This study investigated the metabolic effects of malathion (cytochrome P450 inhibitor) and 4-chloro-7-nitrobenzofurazan [NBD-Cl; glutathione S-transferase inhibitor] on the S-metolachlor-resistant A. palmeri biotype. Root elongation of the resistant biotype was 20% more inhibited by treatment of NBD-Cl (50 nM) and S-metolachlor (2 µM) in mixture than by treatment of S-metolachlor alone. Metabolites of S-metolachlor were 1.4-12.1 times greater produced in the resistant biotype for 7 d than in the susceptible standard. Production of cerotic acid, one of the very-long-chain fatty acids containing 26 carbons, was more reduced in the susceptible standard (3.8-fold) than in the resistant biotype (1.8-fold) by S-metolachlor treatment. Conclusively, evolution of S-metolachlor resistance observed in this study was likely associated with improved activity of glutathione S-transferases. Further studies are needed to genetically evaluate plant endogenous enzymes involving cerotic acid production.

Peer review of the pesticide risk assessment of the active substance S-metolachlor excluding the assessment of the endocrine disrupting properties.

The conclusions of the European Food Safety Authority (EFSA) following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State Germany and co-rapporteur Member State France for the pesticide active substance S-metolachlor are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012, as amended by Commission Implementing Regulation (EU) No 2018/1659. In September 2022, the European Commission asked EFSA to deliver its conclusion on the available outcomes of the assessments in all areas excluding the full assessment of endocrine disrupting properties as several critical areas of concern related to the protection of the environment were identified. The conclusions were reached on the basis of the evaluation of the representative uses of S-metolachlor as a herbicide on maize and sunflower. The reliable end points, appropriate for use in regulatory risk assessment are presented. Missing information identified as being required by the regulatory framework is listed. The concerns identified are presented.

Evaluation of the herbicide glyphosate, (aminomethyl)phosphonic acid, and glyphosate-based formulations for genotoxic activity using in vitro assays.

Glyphosate, the most heavily used herbicide world-wide, is applied to plants in complex formulations that promote absorption. The National Toxicology Program reported in 1992 that glyphosate, administered to rats and mice at doses up to 50,000 ppm in feed for 13 weeks, showed little evidence of toxicity, and no induction of micronuclei was observed in the mice in this study. Subsequently, mechanistic studies of glyphosate and glyphosate-based formulations (GBFs) that have focused on DNA damage and oxidative stress suggest that glyphosate may have genotoxic potential. However, few of these studies directly compared glyphosate to GBFs, or effects among GBFs. To address these data gaps, we tested glyphosate, glyphosate isopropylamine (IPA), and (aminomethyl)phosphonic acid (AMPA, a microbial metabolite of glyphosate), 9 high-use agricultural GBFs, 4 residential-use GBFs, and additional herbicides (metolachlor, mesotrione, and diquat dibromide) present in some of the GBFs in bacterial mutagenicity tests, and in human TK6 cells using a micronucleus assay and a multiplexed DNA damage assay. Our results showed no genotoxicity or notable cytotoxicity for glyphosate or AMPA at concentrations up to 10 mM, while all GBFs and herbicides other than glyphosate were cytotoxic, and some showed genotoxic activity. An in vitro to in vivo extrapolation of results for glyphosate suggests that it is of low toxicological concern for humans. In conclusion, these results demonstrate a lack of genotoxicity for glyphosate, consistent with observations in the NTP in vivo study, and suggest that toxicity associated with GBFs may be related to other components of these formulations.