Role of sediments in modifying the toxicity of two Roundup formulations to six species of larval anurans

Abstract

The role of sediment in modifying the toxicity of the original formulation of Roundup® and Roundup WeatherMAX® was examined in aqueous laboratory tests. Six species of anurans (Bufo fowleri, Hyla chrysoscelis, Rana catesbeiana, Rana clamitans, Rana sphenocephala, and Rana pipiens) were exposed at Gosner stage 25 to concentrations of the 2 herbicide formulations in 96-h, static, nonrenewal experiments in the presence and absence of sediment. All species tested had lower median lethal concentration values in water-only exposures of both formulations compared with exposures with sediment. Sediment significantly altered the potency slopes in all tests with the exceptions of H. chrysoscelis and R. clamitans when exposed to the original formulation of Roundup and H. chrysoscelis and R. sphenocephala when exposed to Roundup WeatherMAX. Thresholds were significantly different in all tests, including those in which potency slopes did not differ. Based on water-sediment exposures of the original formulation of Roundup, all 6 species tested had a margin of safety when compared with the predicted environmental concentration of the highest label application rate. Of the 6 species, 5 had a margin of safety when exposed to Roundup WeatherMAX. During incidental exposures in the field, sediments and organic matter present in aquatic systems provide significant sources of environmental ligands. If used according to label instructions, both herbicides should pose minimal risk to anuran amphibians in actual field applications. Environ Toxicol Chem 2014;33:2616-2620. © 2014 SETAC.

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate‐containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure

“…Based on the results from our study , and those of others , it appears that adsorption of POEA to sediment is not rapidly reversible and may even reduce bioavailability for benthos. This is consistent with observations from studies that have attempted to extract MON 0818 from soils and sediment for analytical purposes .…”

“…To their surprise, they observed differential effects, with reduced toxicity to the floating macrophyte Lemna minor, but enhanced toxicity to the cladoceran Daphnia pulex, which the authors attributed to the filter-feeding and the binding of the formulation components to filtered suspended particles. The consensus since has been that sediments reduce the toxic effects of glyphosate formulations [19,22,23,[36][37][38]. Of these studies, 3 [36][37][38] focused their attention on amphibians, whereas the other 3 [19,22,23] assessed the effect of sediment on toxicity to cladocerans.…”

“…The consensus since has been that sediments reduce the toxic effects of glyphosate formulations [19,22,23,[36][37][38]. Of these studies, 3 [36][37][38] focused their attention on amphibians, whereas the other 3 [19,22,23] assessed the effect of sediment on toxicity to cladocerans. Only Tsui and Chu [22] included a benthic invertebrate (Hyalella azteca) in their study.…”

The toxicity of glyphosate alone and glyphosate–surfactant mixtures to western toad (Anaxyrus boreas) tadpoles

“…Even fewer studies have examined the toxicity of aquatic herbicides. A number of recent studies have examined the effects of glyphosate-based herbicides on amphibians [10][11][12][13][14][15][16][17], but did not examine how the toxicity changed when a surfactant was added. Previous studies conducted on nonamphibian test species suggest that glyphosate-based herbicide mixtures are more toxic than glyphosate alone [18][19][20][21].…”

Supportive use of cyclodextrins as decontamination agents for herbicides: the case of fenoxaprop‐p‐ethyl

“…However, the US Environmental Protection Agency regulates the inclusion of certain ingredients in adjuvant formulations, but it does not stringently test and regulate the manufacture and use of adjuvant products (as they do for herbicides and other pesticides) . Actually, if the so‐called inert compounds such as surfactants, co‐solvents, stabilizers, preservatives, and buffers, improve the AI properties (such as solubility, penetration, efficacy, chemical and thermal stability, biodegradability, smell, volatility, soil mobility, persistence, and poor wettability), on the other hand, they may amplify its adverse effects . It is therefore necessary to evaluate the toxicity of the formulations as a whole rather than focusing only on AI and to propose new functional ingredients capable of improving the AI properties without increasing its toxicity profile, but if anything, minimizing the toxicity.…”