Residues of glyphosate (N-phosphonomethylglycine) and its metabolite aminomethylphosphonic acid (AMPA) were followed on three forested sites in Oregon, Michigan, and Georgia. Eight-hectare residual stands of low-quality hardwoods were treated with 4.12 kgha glyphosate ae applied aerially in late summer. Residues were highest in upper crown foliage. Overstory reduced exposure of understory vegetation and streams. Residues in streams were close to the detection limit or undetectable in 3-14 days. Residues in soils were highest where cover was sparse and where litter was removed. No residues were detectable in soil 409 days after treatment; movement below 15 cm was negligible. AMPA appeared at low levels in all degrading matrices, including sediments, soon aRer deposition of glyphosate. In pond sediments, both glyphosate and AMPA remained bound and inactive. Residue concentrations in foliage, water, and soil were below levels known to be biologically active in nontarget fauna.

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)

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A new residue method for the analysis of glyphosate and (aminomethyl)phosphonic acid has been validated with an interlaboratory study. Five different analysts from Monsanto Co. and other laboratories participated in testing of five different matrixes: alfalfa forage, cabbage, grapes, soybean grain, environmental water. These were chosen to represent the wide variety of matrixes analyzed for glyphosate-related residues. The cornerstone of the method is concentration and isolation via chelation ion exchange, with subsequent quantitation by HPLC with postcolumn reaction detection. The method was validated over the concentration range from 0.05 to 5.00 ppm with overall analytical recoveries of 80.9 ± 13.8% for glyphosate and 79.2 ± 13.8% for (aminomethyl)phosphonic acid. The coefficient of variation for both analytes was 17%, which fits well with that predicted for the analysis of compounds in this concentration range.

A liquid chromatographic method for determining glyphosate (GLYPH) and its major metabolite aminomethylphosphonic acid (AMPA) in various environmental substrates is described. Ion-exchange column chromatography is coupled with post-column ninhydrin derivatization and absorbance detection at 570 nm. Use of a valve-switching technique allowed quantitation of both analytes in a single chromatographic run and eliminated slow-eluting, coextracted interferences. The method was successfully used to quantitate GLYPH and AMPA in organic and mineral soils, stream sediments, and foliage of 2 hardwood brush species. Mean recovery efficiencies for GLYPH as determined from fortified blank field samples were as follows: bottom sediment 84%, suspended sediment 66%, organic soils 79%, mineral soils 73%, alder leaf litter 81%, salmonberry leaf litter 84%, and artificial deposit collectors 87%. Precision for GLYPH determination was good with less than 14% coefficient of variation on mean recovery for all substrates. Limits of detection were lowest for sediments (0.01 μg/g dry mass) and highest for foliage substrates (0.10 μg/g dry mass). Using this system, 6 samples/person/day were routinely analyzed.