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PubMed2005

Evaluation of transgenic cotton varieties and a glyphosate application on seedling disease incidence.

A study was conducted to determine whether stand densities of transgenic cotton (Gossypium hirsutum) varieties, with or without glyphosate, were similar to conventional varieties of the same lineage group in Georgia and Mississippi. Transgenic and conventional cotton varieties were placed into five lineage groups of related varieties and seedling disease was evaluated in three greenhouse tests and a field trial using Rhizoctonia solani AG-4. Seed vigor was determined by standard germination studies were conducted evaluating conventional and transgenic varieties of similar lineage. Results showed that no interactions occurred for the heights and dry weight data across treatments within the lineage groups in any of the experiments. No interactions were shown between stand densities at different inoculum rates and inoculated versus uninoculated pots (plots). Across all greenhouse studies, stand counts of PM 1220 were similar to the transgenic varieties PM 1220 RR and PM 1220 B/RR with or without a glyphosate application. In the field trial, PM 1220 B/RR + glyphosate had significantly lower stands than all other treatments expect PM 1220 RR (no glyphosate treatment) prior to and after glyphosate application. Stand densities for varieties within the lineage group DPL 5415 were also inconsistent when compared between the greenhouse and field trials with no apparent trends occurring. However, the Coker 312 varieties containing glyphosate tolerance had consistently lower stand counts compared to the conventional variety of Coker 312 but only during the greenhouse studies. Seed germination of Coker 312 could not be correlated with either the greenhouse or field trial data. In general, the commercially available varieties such as PM 1220, DPL 5690, DPL 5415, and DPL 50 with glyphosate tolerance had similar stand count, height, and dry weight data when compared to the conventional varieties from the same lineage group regardless of a glyphosate application. When differences did occur, no consistent trends could be determined within these four lineage groups.

Bacillus thuringiensis↗

PubMed1977

Effect of glyphosate on carrot and tobacco cells.

The growth of suspension-cultured carrot (Daucus carota L.) and tobacco (Nicotiana tabacum L. cv. Xanthi) cells was inhibited by glyphosate (N-[phosphonomethyl]glycine). This inhibition was reversed by adding combinations of phenylalanine, tyrosine, and tryptophan or casein hydrolysate. Casein hydrolysate and phenylalanine + tyrosine + tryptophan were the most effective treatments. Reversal of glyphosate-induced inhibition occurred only if the aromatic amino acids were added during the first 8 days of glyphosate incubation. Glyphosate uptake was not reduced when the aromatic amino acids or casein hydrolysate were added.Even though phenylalanine biosynthesis is a suggested site for glyphosate action, inhibitory levels of glyphosate did not lower free phenylalanine concentrations in carrot cells within 10 days. (14)C-Phenylalanine studies indicated that the metabolic pool size was, likewise, not decreased.In carrot cells total free amino acids increased within 6 hours after glyphosate addition. Cell protein levels declined within 48 hours following glyphosate treatment.Studies on (14)C-thymidine and (14)C-uridine incorporation were complicated by rapid metabolism of these compounds to (14)CO(2).

Journal Article↗

PubMed1988

Glyphosate Tolerance in Tobacco (Nicotiana tabacum L.).

A glyphosate-tolerant tobacco cell line, Nicotiana tabacum L. Indiana (I7), was selected from the glyphosate-sensitive Wisconsin 38 (W38) line through a single step exposure to the herbicide. Tolerance and growth characteristics of I7 cells were the same for cells maintained for more than 1 year in the presence or absence of glyphosate. Glyphosate tolerance levels were constant through the growth cycle. Tolerance is not due to reduced uptake of glyphosate. Shikimate levels in I7 and W38 cells maintained in glyphosate-free medium were similar, whereas W38 cells accumulated 46 times more shikimate than I7 cells, when cells of both lines were exposed to the herbicide. Glyphosate treatment caused increased levels of aromatic amino acids in W38 cells and slightly lower levels in I7 cells. Specific activities of dehydroquinate synthase, shikimate dehydrogenase, and shikimate kinase were similar in the two cell types, whereas DAHP synthase and EPSP synthase specific activities were elevated in I7 cells. Plants regenerated from I7 cells retained tolerance to glyphosate.

Journal Article↗

PubMed2005

Technical performance of some commercial glyphosate-resistant crops.

Glyphosate-resistant (GR) crops have been sold commercially in the USA since 1996. The use of glyphosate alone or with conventional pre- and post-emergence herbicides with different modes of action gives growers many options for affordable, safe, easy, effective wide-spectrum weed control. Despite the overwhelming popularity of this technology, technical issues have surfaced from time to time as US growers adopt these crops for use on their farms. The types of concern raised by growers vary from year to year depending on the crop and the environment, but include perceptions of increased sensitivity to diseases, increased fruit abortion, reduced pollination efficiency, increased sensitivity to environmental stress, and differences in yield and agronomic characteristics between transgenic and sister conventional varieties. Although several glyphosate-resistant crops are commercially available, maize, soybean and cotton constitute the largest cultivated acreage and have likewise been associated with the highest number of technical concerns. Because glyphosate is rapidly translocated to and accumulates in metabolic sink tissues, reproductive tissues and roots are particularly vulnerable. Increased sensitivity to glyphosate in reproductive tissues has been documented in both glyphosate-resistant cotton and maize, and results in reduced pollen production and viability, or increased fruit abortion. Glyphosate treatments have the potential to affect relationships between the GR crop, plant pathogens, plant pests and symbiotic micro-organisms, although management practices can also have a large impact. Despite these potential technical concerns, this technology remains popular, and is a highly useful tool for weed control in modern crop production.

Crops, Agricultural↗

PubMed2005

Evolution of a microbial acetyltransferase for modification of glyphosate: a novel tolerance strategy.

N-Acetylation is a modification of glyphosate that could potentially be used in transgenic crops, given a suitable acetyltransferase. Weak enzymatic activity (k(cat) = 5 min(-1), K(M) = 1 mM) for N-acetylation of glyphosate was discovered in several strains of Bacillus licheniformis (Weigmann) Chester by screening a microbial collection with a mass spectrometric assay. The parental enzyme conferred no tolerance to glyphosate in any host when expressed as a transgene. Eleven iterations of DNA shuffling resulted in a 7000-fold improvement in catalytic efficiency (k(cat)/K(M)), sufficient for conferring robust tolerance to field rates of glyphosate in transgenic tobacco and maize. In terms of k(cat)/K(M), the native enzyme exhibited weak activity (4-450% of that with glyphosate) with seven of the common amino acids. Evolution of the enzyme towards an improved k(cat)/K(M) for glyphosate resulted in increased activity toward aspartate (40-fold improved k(cat)), but activity with serine and phosphoserine almost completely vanished. No activity was observed among a broad sampling of nucleotides and antibiotics. Improved catalysis with glyphosate coincided with increased thermal stability.

Acetyltransferases↗

PubMed2005

Efficacy and fate of glyphosate on Swedish railway embankments.

The herbicide glyphosate, N-(phosphonomethyl)glycine, as Spectra (240 g AI litre(-1) SL; Monsanto Europe AB), RoundUp (360 g AI litre(-1) SL; Monsanto) and RoundUp Bio (360 g AI litre(-1) SL; Monsanto), have been used for weed control on Swedish railway embankments since 1986. This article summarizes results from studies of the weed effect and behaviour of glyphosate for the period 1984-2003. Studies on a railway embankment with a range of application rates showed excellent weed control at 5 litre ha(-1) of RoundUp Bio. The appearance of glyphosate and its metabolite AMPA [(aminomethyl)phosphonic acid] in the embankment, eg mobility and persistence, was also studied. Mobility was low in most cases, the main proportion of both glyphosate and AMPA being found in the upper 30-cm layer although minor amounts penetrated to lower depths. The 50% disappearance time of glyphosate was generally <5 months in railway embankments but cases with longer persistence were found. Transport to the groundwater was observed for glyphosate and AMPA in groundwater pipes along tracks. Downward transport appears to be dependent on the application rate, which should not exceed 3 litre ha(-1) of RoundUp Bio to avoid groundwater contamination. A lower rate of glyphosate mixed with a low rate of another herbicide may achieve acceptable weed control and be environmentally safer.

Environment↗

PubMed2005

Mobility and leaching of glyphosate: a review.

There is currently concern that glyphosate, a strongly sorbing non-selective herbicide which is widely used in Europe, may be leached from the root zone into drainage water and groundwater. The purpose of this review is to present and discuss the state of knowledge with respect to the mobility and leaching of glyphosate from agricultural soils. Specific attention is given to the adsorption behaviour of glyphosate and the analysis of available studies on glyphosate transport. In addition, there are a number of experimental and numerical studies indicating that other strongly sorbing substances may be transported rapidly to the sub-surface. The experimental studies analysed in the paper encompass column-, lysimeter- and field-scale experiments on glyphosate transport. The experimental findings, combined with transport studies on other strongly sorbing pesticides in the literature, support the hypothesis that transport of glyphosate may be caused by an interaction of high rainfall events shortly after application on wet soils showing the presence of preferential flow paths. Concentrations of glyphosate in European groundwater have been reported occasionally but monitoring is still limited.

Adsorption↗

PubMed1992

Conifer seedling nursery worker exposure to glyphosate.

This study addresses the measurements of glyphosate exposure received by 14 workers employed at two tree nurseries. The applicators, weeders, and scouts monitored all wore normal work clothing, which for applicators was a protective suit, rubber gloves and boots. Measurements were made of the glyphosate that was dislodged from conifer seedlings during water rinses taken twice weekly from May through August. Only 1 of these 78 dislodgeable residue samples were positive for glyphosate. Nine cotton gauze patches were attached to the clothing of each worker one day per week during this same period. Hand washes were taken on the same day that patches were worn. Most patches and hand washes from applicators and weeders contained measurable amounts of glyphosate. Analyses of individual patches showed that the body portions receiving the highest exposure were ankles and thighs. For scouts only 1 of 23 hand washes contained glyphosate. To provide a measure of the exposure occurring via all exposure routes (dermal, ingestion, and inhalation) an analysis was made of the total urine excreted. For most workers a daily total urine collection was made for 12 consecutive weeks. Urine analysis, the biological monitoring tool used to assess the total amount absorbed via all avenues, did not reveal any positive samples. The lower limit of method validation for glyphosate in the urine samples was 0.01 micrograms/ml. High rainfall, or irrigation as needed, in conjunction with normal field dissipation avenues and worker training were cited as contributing factors for the low amounts of glyphosate exposure found.(ABSTRACT TRUNCATED AT 250 WORDS)

Environmental Monitoring↗

PubMed1992

Glyphosate selected amplification of the 5-enolpyruvylshikimate-3-phosphate synthase gene in cultured carrot cells.

CAR and C1, two carrot (Daucus carota L.) suspension cultures of different genotypes, were subjected to stepwise selection for tolerance to the herbicide glyphosate [(N-phosphonomethyl)glycine]. The specific activity of the target enzyme, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), as well as the mRNA level and copy number of the structural gene increased with each glyphosate selection step. Therefore, the tolerance to glyphosate is due to stepwise amplification of the EPSPS genes. During the amplification process, DNA rearrangement did not occur within the EPSPS gene of the CAR cell line but did occur during the selection step from 28 to 35 mM glyphosate for the C1 cell line, as determined by Southern hybridization of selected cell DNA following EcoRI restriction endonuclease digestion. Two cell lines derived from a previously selected glyphosate-tolerant cell line (PR), which also had undergone EPSPS gene amplification but have been maintained in glyphosate-free medium for 2 and 5 years, have lost 36 and 100% of the increased EPSPS activity, respectively. Southern blot analysis of these lines confirms that the amplified DNA is relatively stable in the absence of selection. These studies demonstrate that stepwise selection for glyphosate resistance reproducibly produces stepwise amplification of the EPSPS genes. The relative stability of this amplification indicates that the amplified genes are not extrachromosomal.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2006

Simultaneous substitution of Gly96 to Ala and Ala183 to Thr in 5-enolpyruvylshikimate-3-phosphate synthase gene of E. coli (k12) and transformation of rapeseed (Brassica napus L.) in order to make tolerance to glyphosate.

Glyphosate is a non-selective broad-spectrum herbicide that inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). This is a key enzyme in the aromatic amino acid biosynthesis pathway of microorganisms and plants. The manipulation of bacterial EPSPS gene in order to reduce its affinity for glyphosate, followed by its transfer to plants is one of the most effective approaches for the production of glyphosate-tolerant plants. In this study, we chose to focus on amino acid residues glycine96 and alanine183 of the E. coli (k12) EPSPS enzyme. These two amino acids are important residues for glyphosate binding. We used site directed mutagenesis (SDM) to induce point mutations in the E. coli EPSPS gene, in order to convert glycine96 to alanine (Gly96Ala) and alanine183 to threonine (Ala183Thr). After confirming the mutation by sequencing, the altered EPSPS gene was transferred to rapeseed (Brassica napus L.) via Agrobacterium-mediated transformation. The transformed explants were screened in shoot induction medium containing 25 mg L-1 kanamycin. Glyphosate tolerance was assayed in putative transgenic plants. Statistical analysis of data showed that there was a significant difference between the transgenic and control plants. It was observed that transgenic plants were resistant to glyphosate at a concentration of 10 mM whereas the non-transformed control plants were unable to survive 1 mM glyphosate. The presence and copy numbers of the transgene were confirmed with PCR and Southern blotting analysis, respectively.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed1987

Glyphosate sensitivity of 5-enol-pyruvylshikimate-3-phosphate synthase from Bacillus subtilis depends upon state of activation induced by monovalent cations.

The 5-enol-pyruvylshikimate-3-phosphate (EPSP) synthase from Bacillus subtilis was activated by monovalent cations, catalytic activity being negligible in the absence of monovalent cations. The order of cation effectiveness (NH4+ greater than K+ greater than Rb+ greater than Na+ = Cs+ = Li+) indicated that the extent of activation was directly related to the unhydrated cation radius. Ammonium salts, at physiological concentrations, were dramatically more effective than other cations. Activation by ammonium was instantaneous, was not influenced by the counter ion, and gave a hyperbolic saturation curve. Hill plots did not show detectable cooperativity in the binding of ammonium. Double-reciprocal plots indicated that ammonium increases the maximal velocity and decreases the apparent Michaelis constants of EPSP synthase with respect to both phosphoenol pyruvate (PEP) and shikimate 3-phosphate (S3P). A direct relationship between sensitivity to inhibition by glyphosate and the activation state of EPSP synthase was demonstrated. Hill plots indicated a single value for glyphosate binding throughout the range of ammonium activation. Double-reciprocal plots of substrate saturation data obtained with ammonium-activated enzyme in the presence of glyphosate showed glyphosate to behave as a competitive inhibitor with respect to PEP and as a mixed-type inhibitor relative to S3P. The increased glyphosate sensitivity of ammonium-activated EPSP synthase is attributed to a lowering of the inhibitor constant of glyphosate with respect to PEP. Erroneous underestimates of sensitivities of some bacterial EPSP synthases to inhibition by glyphosate may result from failure to recognize cation requirements of EPSP synthases.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2005

Alterations induced by glyphosate on lupin photosynthetic apparatus and nodule ultrastructure and some oxygen diffusion related proteins.

The effects of glyphosate on protein metabolism, mesophyll cell ultrastructure and nodule ultrastructure and functioning of Lupinus albus cv. Multolupa inoculated with Bradyrhizobium sp. (Lupinus) were investigated. Young leaves and nodules were especially affected because these organs act as sinks of the herbicide. The alterations on nodular and chloroplast ultrastructure varied depending on herbicide concentration and time of exposure. After 3 days of 2.5 mM glyphosate application some toxic effects were detected. The most important alterations on nodules were the progressive cellular degradation of plant and bacteroidal cytosol and the rupture of bacteroidal membrane, whilst the peribacteroid membrane of the symbiosomes was preserved. This is the first report on the effect of glyphosate on legume-nodule ultrastructure. Glyphosate inhibited B. sp. (Lupinus) growth at concentrations higher than 62.5 microM. In the mesophyll cells, gradual disorganization of grana and intergrana was observed, loosing the parallel alignment with the chloroplast axis. As in nodules, degradation of membrane systems was observed, with the deformation, and even the rupture, of the tonoplast. These progressive effects were similar to those described in senescence processes. The adverse effects produced on infected zone can be due both to a direct effect of the herbicide on microsymbiont and to an indirect effect of glyphosate action on photosynthetic apparatus. Glyphosate produced changes in nodule cytosol and bacteroid proteins content and polypeptide pattern of leaves and nodules. With respect to proteins related to the oxygen diffusion mechanism, a large decrease in leghemoglobin and glycoproteins (recognized by antibodies MAC236 and MAC265) content was detected, which suggests that the oxygen diffusion mechanisms were also affected by glyphosate.

Diffusion↗

PubMed2006

Investigation of the mechanism of chlorination of glyphosate and glycine in water.

The chlorination reactions of glyphosate and glycine in water were thoroughly studied. Utilizing isotopically enriched (13C and 15N) samples of glycine and glyphosate and 1H, 13C, 31P, and 15N NMR spectroscopy we were able to identify all significant terminal chlorination products of glycine and glyphosate, and show that glyphosate degradation closely parallels that of glycine. We have determined that the C1 carboxylic acid carbon of glycine/glyphosate is quantitatively converted to CO2 upon chlorination. The C2 methylene carbon of glycine/glyphosate is converted to CO2 and methanediol. The relative abundance of these two products is a function of the pH of the chlorination reactions. Under near neutral to basic reaction conditions (pH 6-9), CO2 is the predominant product, whereas, under acidic reaction conditions (pH < 6) the formation of methanediol is favored. The C3 phosphonomethylene carbon of glyphosate is quantitatively converted to methanediol under all conditions tested. The nitrogen atom of glycine/glyphosate is transformed into nitrogen gas and nitrate, and the phosphorus moiety of glyphosate produces phosphoric acid upon chlorination. In addition to these terminal chlorination products, a number of labile intermediates were also identified including N-chloromethanimine, N-chloroaminomethanol, and cyanogen chloride. The chlorination products identified in this study are not unique to glyphosate and are similar to those expected from chlorination of amino acids, proteins, peptides, and many other natural organic matters present in drinking water.

Carbon Dioxide↗

PubMed2002

Linker-assisted immunoassay and liquid chromatography/mass spectrometry for the analysis of glyphosate.

A novel, sensitive, linker-assisted enzyme-linked immunosorbent assay (L'ELISA) was compared to on-line solid-phase extraction (SPE) with high-performance liquid chromatography/mass spectrometry (HPLC/MS) for the analysis of glyphosate in surface water and groundwater samples. The L'ELISA used succinic anhydride to derivatize glyphosate, which mimics the epitotic attachment of glyphosate to horseradish peroxidase hapten. Thus, L'ELISA recognized the derivatized glyphosate more effectively (detection limit of 0.1 microg/L) and with increased sensitivity (10-100 times) over conventional ELISA and showed the potential for other applications. The precision and accuracy of L'ELISA then was compared with on-line SPE/HPLC/MS, which detected glyphosate and its degradate derivatized with 9-fluorenylmethyl chloroformate using negative-ion electrospray (detection limit 0.1 microg/ L, relative standard deviation +/- 15%). Derivatization efficiency and matrix effects were minimized by adding an isotope-labeled glyphosate (2-13C15N). The accuracy of L'EUSA gave a false positive rate of 18% between 0.1 and 1.0 microg/L and a false positive rate of only 1% above 1.0 microg/L The relative standard deviation was +/- 20%. The correlation of L'ELISA and HPLC/MS for 66 surface water and groundwater samples was 0.97 with a slope of 1.28, with many detections of glyphosate and its degradate in surface water but not in groundwater.

Chromatography, High Pressure Liquid↗

PubMed1995

Reevaluating glyphosate as a transition-state inhibitor of EPSP synthase: identification of an EPSP synthase.EPSP.glyphosate ternary complex.

Numerous studies have confirmed that glyphosate forms a tight ternary complex with EPSP synthase and shikimate 3-phosphate. It has been proposed [Anton, D., Hedstrom, L., Fish, S., & Abeles, R. (1983) Biochemistry 22, 5903-5908; Steinrücken, H. C., & Amrhein, N. (1984) Eur. J. Biochem. 143, 351-357] that in this complex glyphosate functions as a transition-state analog of the putative phosphoenolpyruvoyl oxonium ion. For this to be true, glyphosate must occupy the space in the enzyme active site that is normally associated with PEP and, through turnover, the carboxyvinyl group of the product EPSP. According to this model, one would predict that, in the reverse EPSP synthase reaction with EPSP and phosphate as substrates, there should be little if any interaction of glyphosate with enzyme or enzyme.substrate complexes. In contrast to this expectation, rapid gel filtration experiments provided direct evidence that glyphosate could be trapped on the enzyme in the presence of EPSP to form a ternary complex of EPSPS.EPSP.glyphosate. The experimentally determined stoichiometry for this complex, 0.62 equiv of glyphosate/mole of EPSPS, is similar to that found for the EPSPS.S3P.glyphosate ternary complex (0.66). This direct binding result was corroborated and quantitated by fluorescence titration experiments which demonstrated that glyphosate forms a reasonably tight (Kd = 56 +/- 1 microM) ternary complex with enzyme and EPSP. This finding was further verified, and its impact on substrate turnover analyzed, by steady-state kinetics. Glyphosate was found to be an uncompetitive inhibitor versus EPSP with Kii(app) = 54 +/- 2 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed1996

An EPSP synthase inhibitor joining shikimate 3-phosphate with glyphosate: synthesis and ligand binding studies.

A novel EPSP synthase inhibitor 4 has been designed and synthesized to probe the configurational details of glyphosate recognition in its herbicidal ternary complex with enzyme and shikimate 3-phosphate (S3P). A kinetic evaluation of the new 3-dephospho analog 12, as well as calorimetric and (31)P NMR spectroscopic studies of enzyme-bound 4, now provides a more precise quantitative definition for the molecular interactions of 4 with this enzyme. The very poor binding, relative to 4, displayed by the 3-dephospho analog 12 is indicative that 4 has a specific interaction with the S3P site. A comparison of Ki(calc) for 12 versus the Ki(app) for 4 indicates that the 3-phosphate group in 4 contributes about 4.8 kcal/mol to binding. This compares well with the 5.2 kcal/mol which the 3-phosphate group in S3P contributes to binding. Isothermal titration calorimetry demonstrates that 4 binds to free enzyme with an observed Kd of 0.53 +/- 0.04 microM. As such, 4 binds only 3-fold weaker than glyphosate and about 150-fold better than N-methylglyphosate. Consequently, 4 represents the most potent N-alkylglyphosate derivative identified to date. However, the resulting thermodynamic binding parameters clearly demonstrate that the formation of EPSPS x 4 is entropy driven like S3P. The binding characteristics of 4 are fully consistent with a primary interaction localized at the S3P subsite. Furthermore, (31)P NMR studies of enzyme-bound 4 confirm the expected interaction at the shikimate 3-phosphate site. However, the chemical shift observed for the phosphonate signal of EPSPS x 4 is in the opposite direction than that observed previously when glyphosate binds with enzyme and S3P. Therefore, when 4 occupies the S3P binding site, there is incomplete overlap at the glyphosate phosphonate subsite. As a glyphosate analog inhibitor, the potency of 4 most likely arises from predominant interactions which occur outside the normal glyphosate binding site. Consequently, 4 is best described as an S3P-based substrate-analog inhibitor. These combined results corroborate the previous kinetic model [Gruys, K. J., Marzabadi, M. R., Pansegrau, P. D., & Sikorski, J. A. (1993) Arch. Biochem. Biophys. 304, 345-351], which suggested that 4 interacts well with the S3P subsite but has little, if any, interaction at the expected glyphosate phosphonate or phosphoenolpyruvate-Pi subsites.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2002

An analysis of glyphosate data from the California Environmental Protection Agency Pesticide Illness Surveillance Program.

Glyphosate is among the pesticides most frequently reported to the California EPA Pesticide Illness Surveillance Program. We analyzed glyphosate-related calls to the Pesticide Illness Surveillance Program in order to assess the number of reports involving systemic symptoms and to better understand the nature and severity of reported cases. Data on glyphosate and other pesticides are available for the years 1982-1997 including: type of exposure (agricultural/other); target organ(s) affected (skin/eye/respiratory/systemic); exposure(s); an assessment of causal relationship (possible, probable, or definite); and limited medical text. Of 815 total glyphosate calls, most involved topical irritation of the eye (n = 399), skin (n = 250), upper airway (n = 7), or combinations of these sites (n = 32) without systemic symptoms. Of the 187 systemic cases, only 22 had symptoms recorded as probably or definitely related to glyphosate exposure alone. The reported symptoms were not severe, expected to be limited in duration, and frequently inconsistent with the route of exposure and/or previous experience with glyphosate. We conclude that call volume is not a reliable indicator of the actual incidence or severity of glyphosate-related incidents in California.

Accidents, Occupational↗

PubMed2003

Leaching of pesticides through normal-tillage and low-tillage soil--a lysimeter study. II. Glyphosate.

Glyphosate is a widely used non-selective herbicide. Leaching of glyphosate (N-(phosphonomethyl)glycine) and/or its metabolite AMPA (aminomethylphosphonic acid) was studied in four lysimeters, two of them being replicates from a low-tillage field (lysimeter 3 and 4), the other two being replicates from a normal tillage field (lysimeter 5 and 6). In both cases the soil was a sandy loam soil with 13-14% clay. The lysimeters had a surface area of 0.5 m2 and a depth of 110 cm. Lysimeter 3 and 4 were sprayed with a mixture of 14C-labelled glyphosate and unlabelled glyphosate, while lysimeter 5 and 6 were sprayed with unlabelled glyphosate. The spraying took place September 18, 1997. The total amount of glyphosate sprayed onto each lysimeter was 40 mg, corresponding to 0.8 kg active ingredient per ha. The lysimeters were installed in an outdoor system in Research Centre Flakkebjerg and were thus exposed to normal climatic conditions of the area. A mean of 260 l drainage water were collected from lysimeter 3 and 4 and a mean of 375 litres from lysimeter 5 and 6. The mean yearly concentration of leached glyphosate and/or AMPA was significantly below 0.1 microg/l from both sets of lysimeters, and thus no significant difference between the two lysimeter sets was shown. However, in both sets of lysimeters several single findings at concentrations above 0.1 microg/l was seen, which might be due to the leaching of particle-bound compounds. A significant difference between the soil residual concencentrations of AMPA was seen, the higher concentration was found in the set of lysimeter where low-tillage had been practiced and where Round Up had been used several times in the years before sampling of the lysimeter soil.

Carbon Radioisotopes↗