Toxicity of glyphosate and triclopyr using the Frog Embryo Teratogenesis Assay-Xenopus

That effects of glyphosate ([N-phosphonomethyl]glycine) and triclopyr ([[3, 5,6-trichloro-2-pyridinyl]oxy]acetic acid) on the embryonic development of Xenopus laevis were evaluated using Frog Embryo Teratogenesis Assay-Xenopus (FETAX). Rodeo(R), the isopropylamine (ipa) salt of glyphosate formulated without a surfactant was found to be the least toxic, with a LC5 and LC50 o f 3.779 and 5.407 mg acid equivalent (AE)/L, respectively. The LC5 and LC50 of Roundup(R), the ipa salt of glyphosate formulated with a surfactant, wa s 6.4 and 9.4 mg AE/L, respectively. The surfactant component of Roundup, p olyoxyethylenenmine (POEA), had a LC5 and LC50 of 2.2 and 2.7 mg/L, respect ively. Garlon(R) 3A, the triethylamine salt of triclopyr, had a LC5 and LC5 0 of 119 and 162.5 mg AE/L, respectively. The LC5 and LC50 of Garlon 4(R), the butoxyethyl cater of triclopyr, was 6.7 and 9.3 mg AE/L, respectively. Considering a theoretical worst case scenario when the highest rates: recom mended for glyphosate (12 L of Roundup/ha) or triclopyr (8 L of Garlon/ha) are applied to water 15 cm in depth, the expected environmental concentrati ons calculated on the basis of AE would be 2.8 and 2.6 mg AE/L, respectivel y. The margins of safety (LC5/expected environmental concentrations) for fr og embryos exposed to these concentrations would be approximately 2, 2, 47, and 1,312 fur Roundup, Garlon 4. Garlon 3A, and Rodeo, respectively.