Characterization of chromatin instabilities induced by glyphosate, terbuthylazine and carbofuran using cytome FISH assay

Mapping the key characteristics of carcinogens for glyphosate and its formulations: A systematic review

Glyphosate was classified as a probable human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC) partially due to strong mechanistic evidence in 2015. Since then, numerous studies of glyphosate and its formulations (GBF) have emerged. These studies can be evaluated for cancer hazard identification with the newly described ten key characteristics (KC) of carcinogens approach. Our objective was to assess all in vivo, ex vivo, and in vitro mechanistic studies of human and experimental animals (mammals) that compared exposure to glyphosate/GBF with low/no exposure counterparts for evidence of the ten KCs. A protocol with our methods adhering to PRISMA guidelines was registered a priori (INPLASY202180045). Two blinded reviewers screened all in vivo, ex vivo, and in vitro studies of glyphosate/GBF exposure in humans/mammals reporting any KC-related outcome available in PubMed before August 2021. Studies that met inclusion criteria underwent data extraction conducted in duplicate for each KC outcome reported along with key aspects of internal/external validity, results, and reference information. These data were used to construct a matrix that was subsequently analyzed in the program R to conduct strength of evidence and quality assessments. Of the 2537 articles screened, 175 articles met inclusion criteria, from which we extracted >50,000 data points related to KC outcomes. Data analysis revealed strong evidence for KC2, KC4, KC5, KC6, KC8, limited evidence for KC1 and KC3, and inadequate evidence for KC7, KC9, and KC10. Notably, our in-depth quality analyses of genotoxicity (KC2) and endocrine disruption (KC8) revealed strong and consistent positive findings. For KC2, we found: 1) studies conducted in humans and human cells provided stronger positive evidence than counterpart animal models; 2) GBF elicited a stronger effect in both human and animal systems when compared to glyphosate alone; and 3) the highest quality studies in humans and human cells consistently revealed strong evidence of genotoxicity. Our analysis of KC8 indicated that glyphosate's ability to modulate hormone levels and estrogen receptor activity is sensitive to both exposure concentration and formulation. The modulations observed provide clear evidence that glyphosate interacts with receptors, alters receptor activation, and modulates the levels and effects of endogenous ligands (including hormones). Our findings strengthen the mechanistic evidence that glyphosate is a probable human carcinogen and provide biological plausibility for previously reported cancer associations in humans, such as non-Hodgkin lymphoma. We identified potential molecular interactions and subsequent key events that were used to generate a probable pathway to lymphomagenesis.

Glyphosate Toxicity: In Vivo, In Vitro, and Epidemiological Evidence

Glyphosate is the most applied agricultural chemical worldwide and has become nearly ubiquitous throughout the environment. Glyphosate is an effective herbicide because it disrupts the shikimate pathway, which is responsible for the synthesis of essential amino acids in plants and microorganisms. Given that there is no known target for glyphosate in higher animals, its toxicity to humans and other animals is heavily debated, especially after the 2015 IARC ruling that glyphosate is carcinogenic. Today, a growing body of literature shows in vitro, in vivo, and epidemiological evidence for the toxicity of glyphosate across animal species. With the application of glyphosate increasing globally, it is important to discuss these reports to enable a broader conversation on glyphosate toxicity and its impact on human and environmental health. Here, we summarize the recent glyphosate literature and discuss its implications.

A Review and Update with Perspective of Evidence that the Herbicide Glyphosate (Roundup) is a Cause of Non-Hodgkin Lymphoma

Glyphosate-based formulations (GBFs), such as Roundup, are the most heavily used herbicides in the world. In 2015, the International Agency for Research on Cancer (IARC) concluded that glyphosate and GBFs are probably carcinogenic to humans (group 2A), mainly for non-Hodgkin lymphoma (NHL). However, this finding has been controversial, and most pesticide regulatory agencies have not followed their lead. The purpose of this review was to examine the scientific literature linking exposure to glyphosate and GBFs to the development of NHL, with emphasis on new findings since publication of the IARC report. The epidemiologic studies provide ample evidence for an association between exposure to GBFs and an increased risk of NHL. Animal studies have shown that glyphosate is carcinogenic in rodents and causes NHL in mice. Mechanistic studies have demonstrated that glyphosate and GBFs are genotoxic to human lymphocytes, the normal cell of origin of NHL, both in vitro and in vivo. Genotoxic and other biological effects have also been shown in various animal and cell models with these agents even at low doses. A novel mechanism underlying the specificity of glyphosate for NHL, that is upregulation of the B-cell genome mutator enzyme activation-induced cytidine deaminase, has recently been demonstrated. These findings were evaluated holistically using the guidelines for evaluation of general causation set forth by Bradford Hill. This evaluation provides coherent and compelling evidence that glyphosate and GBFs are a cause of NHL in humans exposed to these agents. These findings should prompt new reviews by pesticide regulatory agencies around the world.

Assessment of Glyphosate Impact on the Agrofood Ecosystem

Agro-industries should adopt effective strategies to use agrochemicals such as glyphosate herbicides cautiously in order to protect public health. This entails careful testing and risk assessment of available choices, and also educating farmers and users with mitigation strategies in ecosystem protection and sustainable development. The key to success in this endeavour is using scientific research on biological pest control, organic farming and regulatory control, etc., for new developments in food production and safety, and for environmental protection. Education and research is of paramount importance for food and nutrition security in the shadow of climate change, and their consequences in food production and consumption safety and sustainability. This review, therefore, diagnoses on the use of glyphosate and the associated development of glyphosate-resistant weeds. It also deals with the risk assessment on human health of glyphosate formulations through environment and dietary exposures based on the impact of glyphosate and its metabolite AMPA-(aminomethyl)phosphonic acid-on water and food. All this to setup further conclusions and recommendations on the regulated use of glyphosate and how to mitigate the adverse effects.

The impact and toxicity of glyphosate and glyphosate-based herbicides on health and immunity

Glyphosate, or N-phosphomethyl(glycine), is an organophosphorus compound and a competitive inhibitor of the shikimate pathway that allows aromatic amino acid biosynthesis in plants and microorganisms. Its utilization in broad-spectrum herbicides, such as RoundUp®, has continued to increase since 1974; glyphosate, as well as its primary metabolite aminomethylphosphonic acid, is measured in soils, water, plants, animals and food. In humans, glyphosate is detected in blood and urine, especially in exposed workers, and is excreted within a few days. It has long been regarded as harmless in animals, but growing literature has reported health risks associated with glyphosate and glyphosate-based herbicides. In 2017, the International Agency for Research on Cancer (IARC) classified glyphosate as "probably carcinogenic" in humans. However, other national agencies did not tighten their glyphosate restrictions and even prolonged authorizations of its use. There are also discrepancies between countries' authorized levels, demonstrating an absence of a clear consensus on glyphosate to date. This review details the effects of glyphosate and glyphosate-based herbicides on fish and mammal health, focusing on the immune system. Increasing evidence shows that glyphosate and glyphosate-based herbicides exhibit cytotoxic and genotoxic effects, increase oxidative stress, disrupt the estrogen pathway, impair some cerebral functions, and allegedly correlate with some cancers. Glyphosate effects on the immune system appear to alter the complement cascade, phagocytic function, and lymphocyte responses, and increase the production of pro-inflammatory cytokines in fish. In mammals, including humans, glyphosate mainly has cytotoxic and genotoxic effects, causes inflammation, and affects lymphocyte functions and the interactions between microorganisms and the immune system. Importantly, even as many outcomes are still being debated, evidence points to a need for more studies to better decipher the risks from glyphosate and better regulation of its global utilization.

Effects of glyphosate exposure on human health: Insights from epidemiological and in vitro studies

Glyphosate (GLY) is a broad-spectrum, post-emergent, non-selective and synthetic universal herbicide, whose commercial formulations are referred to as glyphosate-based-herbicides (GBHs). These chemicals and their metabolites can be found in soil, air, water, as well as groundwater and food products. This review summarizes to summarize current in vitro and epidemiological studies investigating the effects of GLY exposure on human health. Recent human cell studies have reported several GLY and GBH toxicological effects and have contributed to a better understanding of the deleterious consequences associated with their exposure. However, these detrimental effects are dependent on the cell type, chemical composition, as well as magnitude and time of exposure, among other factors. Moreover, the deleterious effects of GLY exposure on human health were observed in epidemiological studies; however, most of these studies have not determined the GLY dosage to confirm a direct effect. While GLY toxicity is clear in human cells, epidemiological studies investigating individuals exposed to different levels of GLY have reported contradictory data. Therefore, based on currently available in vitro and epidemiological data, it is not possible to confirm the complete safety of GLY use, which will require additional comprehensive studies in animal models and humans.

Glyphosate-based herbicide impairs energy metabolism and increases autophagy in C6 astroglioma cell line

Several investigators demonstrated that glyphosate formulations produce neurotoxicity associated with oxidative stress, alterations in glutamatergic system, inhibition of acetylcholinesterase activity and mitochondrial dysfunction. However, the underlying molecular mechanisms following exposure to this herbicide on astrocytes are unclear. Thus, the aim of the present study was to determine the activity of enzymes related to energy metabolism, in addition to oxidative stress parameters, mitochondrial mass, nuclear area, and autophagy in astrocytes treated with a glyphosate-based herbicide. Our results showed that 24 h exposure to a glyphosate-based herbicide decreased (1) cell viability, (2) activities of mitochondrial respiratory chain enzymes and creatine kinase (CK), (3) mitochondrial mass, and (4) nuclear area in rat astroglioma cell line (C6 cells). However, non-protein thiol (NPSH) levels were increased but catalase activity was not changed in cells exposed to the herbicide at non-cytotoxic concentrations. Low glyphosate concentrations elevated content of cells positive to autophagy-related proteins. Nuclear factor erythroid 2-related factor (Nrf2), NAD(P)H dehydrogenase [quinone] 1 (NQO1) and PTEN-induced kinase 1 (PINK1) labeling were not markedly altered in cells exposed to glyphosate at the same concentrations that an increase in NPSH levels and positive cells to autophagy were found. It is conceivable that mitochondria and CK may be glyphosate-based herbicides targets. Further, autophagy induction and NPSH increase may be mechanisms initiated to avoid oxidative stress and cell death. However, more studies are needed to clarify the role of autophagy in astrocytes exposed to the herbicide and which components of the formulation might be triggering the effects observed here.

Comparative cyto- and genotoxicity assessment of glyphosate and glyphosate-based herbicides in human peripheral white blood cells

Glyphosate is the most heavily applied active compound of agricultural pesticides. It is solely used in more than 750 different glyphosate-based herbicide formulations (GBHs) that also contain other substances, mostly presumed as inert by regulatory agencies. The toxicity of formulations is currently assessed substance by substance, neglecting possible combined effects in mixtures and many of the findings regarding the toxic effects of glyphosate and GBHs to human cells are inconsistent. This is the first study to investigate and compare the cyto- and genotoxic potential of the active ingredient glyphosate and GBHs in human mononuclear white blood (HMWB) cells. HMWB cells were treated for 4 h at 37 °C with increasing concentrations (1-1000 μM) of glyphosate alone and in three GBHs (Roundup Mega, Fozat 480 and Glyfos) to test cytotoxic effect with fluorescent colabelling and genotoxic effect with comet assay. In addition, each concentration was tested with and without metabolic activation using human liver S9 fraction. We found that glyphosate alone does not induce significant cytotoxicity and genotoxicity over the tested concentration range. Contrarily, GBHs induced statistically significant cell death from 250 μM (Roundup Mega and Glyfos) and 500 μM (Fozat 480), as well as statistically significant increase of DNA damage from 500 μM (Roundup Mega and Glyfos) and 750 μM (Fozat 480); however, the latter observation may not be explained by direct DNA injuries, rather due to the high level of cell death (>70%) exerted by the formulations. Metabolic activation significantly increased the DNA damage levels induced by Glyfos, but not of the other GBHs and of glyphosate. The differences observed in the toxic pattern of formulations and the active principle may be attributed to the higher cytotoxic activity of other ingredients in the formulations or to the interaction of them with the active ingredient glyphosate. Hence, further investigation of formulations is crucial for assessing the true health risks of occupational and environmental exposures.

Base excision repair (OGG1 and XRCC1) and metabolism (PON1) gene polymorphisms act on modulation of DNA damage and immune parameters in tobacco farmers

Pesticides are one of the most frequently investigated chemical, due to their multiple uses in agricultural and public health areas. This study evaluates lymphocytes CBMN (cytokinesis-block micronucleus cytome assay), inflammatory markers, inorganic elements in blood samples, and the relationship of these parameters with XRCC1Arg194Trp, OGG1Ser326Cys and PON1Gln192Arg polymorphisms in a population of tobacco farmers. The study population comprised 129 agricultural workers exposed to pesticides and 91 nonexposed. Farmers had significantly increased NPB (nuclear plasmatic bridge), MN (micronucleus) and NBUD (nuclear bud) frequencies, as well as IL-6 (interleukin 6) and TNF-α (tumor necrosis factor alpha) serum levels, and decreased cytokines CD4+/CD8+ ratio. In the exposed group, XRCC1 Trp/- was correlated with decreased NDI (nuclear division index), and OGG1 Cys/- was associated with higher levels of NPB and decreased levels of IL-6. The combined effects of PON1 Arg/- and XRCC1 Arg/Arg were associated with increased NPB frequencies. In addition, the combination of PON1 Arg/- with XRCC1 Trp/- or OGG1 Cys/- influenced in increased levels of necrosis in farmers. Furthermore, tobacco farmers showed a positive correlation between TNF-α levels and NPB, CD4+/CD8+ ratio and NBUD; and IL-6 levels with both MN and NDI. The duration of years of work at tobacco fields was correlated positively with NBUD frequency. Sulfur, chlorine and potassium were found at increased levels in the exposed group when compared to the nonexposed one. These findings provide evidence that tobacco farmers' exposure have increased DNA damage and alter the immune system's response, and that XRCC1 and OGG1 polymorphisms could influence both biomarkers results.

Effects of the chloro-s-triazine herbicide terbuthylazine on DNA integrity in human and mouse cells

Terbuthylazine belongs to the chloro-s-triazine group of herbicides and acts primarily as a photosynthesis inhibitor. The mechanisms of action related to its exposure, relevant both in animals and humans, are still insufficiently investigated. This comprehensive study focused on the outcomes of terbuthylazine exposure at cell level in vitro, and a mice model in vivo. Experiments in vitro were conducted on whole human peripheral blood, isolated lymphocytes, and HepG2 cells exposed for 4 h to terbuthylazine at 8.00, 0.80, and 0.58 ng/mL, which is comparable with current reference values set by the European Commission in 2011. Terbuthylazine cytotoxicity was evaluated using dual fluorescent staining with ethidium bromide and acridine orange on lymphocytes, and CCK-8 colorimetric assay on HepG2 cells. The levels of DNA damage were measured using alkaline and hOGG1-modified comet assays. The potency of terbuthlyazine regarding induction of oxidative stress in vitro was studied using a battery of standard oxidative stress biomarkers. The in vivo experiment was conducted on Swiss albino mice exposed to terbuthlyazine in the form of an active substance and its formulated commercial product Radazin TZ-50 at a daily dose of 0.0035 mg/kg bw for 14 days. Following exposure, the DNA damage levels in leukocytes, bone marrow, liver, and kidney cells of the treated mice were measured using an alkaline comet assay. In vitro results suggested low terbuthylazine cytotoxicity in non-target cells. The highest tested concentration (8.00 ng/mL) reduced lymphocyte viability by 15%, mostly due to apoptosis, while cytotoxic effects in HepG2 cells at the same concentration were negligible. Acute in vitro exposure of human lymphocytes and HepG2 cells to terbuthylazine resulted in low-level DNA instability, as detected by the alkaline comet assay. Further characterization of the mechanisms behind the DNA damage obtained using the hOGG1-modified comet assay indicated that oxidative DNA damage did not prevail in the overall damage. This was further confirmed by the measured levels of oxidative stress markers, which were mostly comparable to control. Results obtained in mice indicate that both the active substance and formulated commercial product of terbuthylazine produced DNA instability in all of the studied cell types. We found that DNA in liver and kidney cells was more prone to direct toxic effects of the parent compound and its metabolites than DNA in leukocytes and bone marrow cells. The overall findings suggest the formation of reactive terbuthylazine metabolites capable of inducing DNA cross-links, which hinder DNA migration. These effects were most pronounced in liver cells in vivo and HepG2 cells in vitro. To provide a more accurate explanation of the observed effects, additional research is needed. Nevertheless, the present study provides evidence that terbuthylazine at concentrations comparable with current reference values possesses toxicological risk because it caused low-level DNA instability, both at cellular and animal organism level, which should be further established in forthcoming studies.

Effects of low doses of glyphosate on DNA damage, cell proliferation and oxidative stress in the HepG2 cell line

We studied the toxic effects of glyphosate in vitro on HepG2 cells exposed for 4 and 24 h to low glyphosate concentrations likely to be encountered in occupational and residential exposures [the acceptable daily intake (ADI; 0.5 μg/mL), residential exposure level (REL; 2.91 μg/mL) and occupational exposure level (OEL; 3.5 μg/mL)]. The assessments were performed using biomarkers of oxidative stress, CCK-8 colorimetric assay for cell proliferation, alkaline comet assay and cytokinesis-block micronucleus (CBMN) cytome assay. The results obtained indicated effects on cell proliferation, both at 4 and 24 h. The levels of primary DNA damage after 4-h exposure were lower in treated vs. control samples, but were not significantly changed after 24 h. Using the CBMN assay, we found a significantly higher number of MN and nuclear buds at ADI and REL after 4 h and a lower number of MN after 24 h. The obtained results revealed significant oxidative damage. Four-hour exposure resulted in significant decrease at ADI [lipid peroxidation and glutathione peroxidase (GSH-Px)] and OEL [lipid peroxidation and level of total antioxidant capacity (TAC)], and 24-h exposure in significant decrease at OEL (TAC and GSH-Px). No significant effects were observed for the level of reactive oxygen species (ROS) and glutathione (GSH) for both treatment, and for 24 h for lipid peroxidation. Taken together, the elevated levels of cytogenetic damage found by the CBMN assay and the mechanisms of primary DNA damage should be further clarified, considering that the comet assay results indicate possible cross-linking or DNA adduct formation.

Telomere measurement in individuals occupationally exposed to pesticide mixtures in tobacco fields

Occupational exposure to pesticides in tobacco fields causes genetic damage in farmers. The aim of this study was to analyze tobacco farmers chronically exposed to low doses of pesticides and nicotine (present in the tobacco leaves) in relation to absolute telomere length (aTL), and explore the influence of lifestyle characteristics, oxidative stress, and inorganic element levels. DNA was isolated from peripheral blood samples from agricultural workers and non-exposed individuals, and aTL was measured by quantitative real time polymerase chain reaction (qPCR) analysis. Oxidative stress (thiobarbituric acid reactive substances [TBARS], which measures oxidative damage to lipids; and toxic equivalent antioxidant capacity [TEAC], which measures total equivalent antioxidant capacity) was evaluated in serum, and inorganic element content was analyzed in whole blood through particle-induced X-ray emission technique. It was found that exposure to pesticides and tobacco smoking had significant effects on aTL. Individuals occupationally exposed to complex mixtures of pesticides in tobacco fields and individuals who smoked had decreased aTL compared with the non-exposed group. TBARS and TEAC were significantly elevated in the exposed group. There were no significant differences in inorganic elements. There was no evidence of an influence of age, gender, consumption of alcoholic beverages, or intake of fruits and vegetables on aTL within the groups. In addition, years of work in the tobacco field in the exposed group did not influence any of the variables analyzed. Although further studies were needed, these results suggested differences in telomere maintenance in tobacco farmers compared with the control group, indicating that telomere length may be a good biomarker of occupational exposure.

In vitro genotoxicity assessment of the synthetic plant growth regulator, 1-naphthaleneacetamide

1-Naphthaleneacetamide (NAAm) is a synthetic plant growth regulator in the auxin family that is widely used in agriculture to promote the growth of numerous fruits, for root cuttings and as a fruit thinning agent. The potential genotoxic effects of NAAm were investigated in vitro by the chromosome aberrations (CAs), and cytokinesis-block micronucleus assays in human peripheral blood lymphocytes (PBLs) for the first time. The human PBLs were treated with 20, 40, 80, and 160 µg/mL of NAAm for 24 and 48 h. The results of this study showed that NAAm significantly induced the formation of structural CA and MN for all concentrations (20, 40, 80 and 160 µg/mL) and treatment periods (24 and 48 h) when compared with the negative and the solvent control. In addition, the higher concentrations of NAAm (80 and 160 µg/mL) caused a statistically significant increase in nuclear bud (NBUD) formation for both 24 and 48 h treatment times. With regard to the cell cycle kinetics, at all the tested concentrations, NAAm caused a statistically significant reduction in the mitotic index (MI) only for 48 h treatment period and also in the nuclear division index (NDI) for both 24 and 48 h treatment periods as compared to the control groups. The reductions in the MI and NDI occured in a concentration-dependent manner for both treatment times. In conclusion, the present results indicate that in the tested experimental conditions, NAAm was genotoxic and cytotoxic on human PBLs in vitro.

In vitro investigation of the genotoxic and cytotoxic effects of thiacloprid in cultured human peripheral blood lymphocytes

Thiacloprid, a neonicotinoid insecticide, is widely used for controlling various species of pests on many crops. The potential genotoxic effects of thiacloprid on human peripheral blood lymphocytes (PBLs) were investigated in vitro by the chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and cytokinesis-block micronucleus (MN) assays. The human PBLs were treated with 75, 150, and 300 μg/mL thiacloprid in the absence and presence of an exogenous metabolic activator (S9 mix). Thiacloprid increased the CAs and SCEs significantly at all concentrations (75, 150, and 300 μg/mL) both in the absence and presence of the S9 mix and induced a significant increase in MN and nucleoplasmic bridge formations at all concentrations for 24 h and at 75 and 150 μg/mL for 48-h treatment periods in the absence of the S9 mix; and at all concentrations in the presence of the S9 mix when compared with the control and solvent control. Thiacloprid was also found to significantly induce nuclear bud (NBUD) formation at 300 μg/mL for 24 h and at 150 μg/mL for 48-h treatment times in the absence of the S9 mix and at the two highest concentrations (150 and 300 μg/mL) in the presence of the S9 mix. Thiacloprid significantly decreased the mitotic index, proliferation index, and nuclear division index for all concentrations both in the absence and presence of the S9 mix.

Micronuclei, nucleoplasmic bridges, and nuclear buds induced in human lymphocytes by the fungicide signum and its active ingredients (boscalid and pyraclostrobin)

The aim of this study was to investigate the genotoxic and cytotoxic potential of the Signum fungicide and its active ingredients (boscalid and pyraclostrobin) on human peripheral blood lymphocytes using the cytokinesis-block micronucleus (CBMN) assay. Micronuclei (MNi), nucleoplasmic bridges (NPBs), nuclear bud (NBUDs) formations, and the cytokinesis-block proliferation index (CBPI) were evaluated in treated lymphocytes in Go (cells were treated and then kept in culture without stimulation for 24 h) and proliferation phases (cells were treated after 44 h culture in medium containing phytohemagglutinin). MN formation in lymphocytes treated in G0 statistically increased at doses of 2, 6, and 25 μg/mL signum; 0.5 and 2 μg/mL boscalid; and 0.5, 1.5, and 2 μg/mL pyraclostrobin; while NPB formation increased at a dose of 0.25 μg/mL pyraclostrobin. All concentrations of each fungicide did not statistically increase NBUD formation, while the cytotoxicity increased the dependent on concentration in lymphocytes treated in G0 . Doses of 0.5, 1, 1.5, and 3 μg/mL signum; 0.5, 1, and 1.5 μg/mL boscalid; and 0.75 μg/mL pyraclostrobin statistically increased the MN formation in proliferating lymphocytes. NPB formation increased in proliferating lymphocytes at doses of 1, 1.5, 2, and 3 μg/mL signum and at a dose of 0.75 μg/mL pyraclostrobin. In addition, a dose of 0.75 μg/mL pyraclostrobin increased NBUD frequencies. Cytotoxicity increased with increasing concentrations of each fungicide. It is concluded that signum, boscalid, and pyraclostrobin may be genotoxic and cytotoxic in vitro human peripheral blood lymphocytes in consideration of each of the two protocols. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 723-732, 2014.

Review of genotoxicity studies of glyphosate and glyphosate-based formulations

An earlier review of the toxicity of glyphosate and the original Roundup™-branded formulation concluded that neither glyphosate nor the formulation poses a risk for the production of heritable/somatic mutations in humans. The present review of subsequent genotoxicity publications and regulatory studies of glyphosate and glyphosate-based formulations (GBFs) incorporates all of the findings into a weight of evidence for genotoxicity. An overwhelming preponderance of negative results in well-conducted bacterial reversion and in vivo mammalian micronucleus and chromosomal aberration assays indicates that glyphosate and typical GBFs are not genotoxic in these core assays. Negative results for in vitro gene mutation and a majority of negative results for chromosomal effect assays in mammalian cells add to the weight of evidence that glyphosate is not typically genotoxic for these endpoints in mammalian systems. Mixed results were observed for micronucleus assays of GBFs in non-mammalian systems. Reports of positive results for DNA damage endpoints indicate that glyphosate and GBFs tend to elicit DNA damage effects at high or toxic dose levels, but the data suggest that this is due to cytotoxicity rather than DNA interaction with GBF activity perhaps associated with the surfactants present in many GBFs. Glyphosate and typical GBFs do not appear to present significant genotoxic risk under normal conditions of human or environmental exposures.

Cytotoxic and DNA-damaging properties of glyphosate and Roundup in human-derived buccal epithelial cells

Glyphosate (G) is the largest selling herbicide worldwide; the most common formulations (Roundup, R) contain polyoxyethyleneamine as main surfactant. Recent findings indicate that G exposure may cause DNA damage and cancer in humans. Aim of this investigation was to study the cytotoxic and genotoxic properties of G and R (UltraMax) in a buccal epithelial cell line (TR146), as workers are exposed via inhalation to the herbicide. R induced acute cytotoxic effects at concentrations > 40 mg/l after 20 min, which were due to membrane damage and impairment of mitochondrial functions. With G, increased release of extracellular lactate dehydrogenase indicative for membrane damage was observed at doses > 80 mg/l. Both G and R induced DNA migration in single-cell gel electrophoresis assays at doses > 20 mg/l. Furthermore, an increase of nuclear aberrations that reflect DNA damage was observed. The frequencies of micronuclei and nuclear buds were elevated after 20-min exposure to 10-20 mg/l, while nucleoplasmatic bridges were only enhanced by R at the highest dose (20 mg/l). R was under all conditions more active than its active principle (G). Comparisons with results of earlier studies with lymphocytes and cells from internal organs indicate that epithelial cells are more susceptible to the cytotoxic and DNA-damaging properties of the herbicide and its formulation. Since we found genotoxic effects after short exposure to concentrations that correspond to a 450-fold dilution of spraying used in agriculture, our findings indicate that inhalation may cause DNA damage in exposed individuals.

The use of FISH-comet to detect c-Myc and TP 53 damage in extended-term lymphocyte cultures treated with terbuthylazine and carbofuran

Terbuthylazine and carbofuran are suspected to cause non-Hodgkin's lymphoma and lung cancer. We evaluated the effects of prolonged exposure to low concentrations on primary DNA damage by comet assay, and on the structural integrity of c-Myc and TP 53 genes by FISH-comet. Another novelty in studying these pesticides' genotoxicity is the use of 14-day extended-term human lymphocyte cultures. Concentrations corresponded to values of ADI and OEL: for terbuthylazine 0.58 ng/ml and 8 ng/ml; for carbofuran 8 ng/ml and 21.6 ng/ml, respectively. A possible effect of metabolic activation (S9) was also considered. Carbofuran treatment induced a significant migration of DNA into the tail in a concentration-dependent manner, while for terbuthylazine the effect was significant only at the higher concentration. Terbuthylazine caused migration of both c-Myc signals into the comet tail. A significant occurrence of TP 53 signals in the tail was observed at 8 ng/ml. Prolonged carbofuran treatment significantly elevated the migration of a single c-Myc signal into the tail in a concentration-dependent manner. With S9, distribution of signals shifted toward increased presence of both signals in tail. Our results showed impaired structural integrity of c-Myc and TP 53 due to prolonged exposure to terbuthylazine and carbofuran.