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

Abstract

Pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. Despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. Land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. Short-term acute toxicity trials were conducted for glyphosate in the form of isopropylamine salt (IPA) alone and mixed with 2 surfactants: Agri-dex and Competitor with western toad (Anaxyrus [Bufo] boreas) tadpoles. Glyphosate IPA mixed with Competitor was 6 times more toxic than glyphosate IPA mixed with Agri-dex, and both mixtures were more toxic than glyphosate IPA alone. The median lethal concentrations reported for 24-h and 48-h exposures were 8279 mg/L (24 h) and 6392 mg/L (48 h) for glyphosate IPA alone; 5092 mg/L (24 h) and 4254 mg/L (48 h) for glyphosate IPA mixed with Agri-dex; and 853 mg/L (24 h) and 711 mg/L (48 h) for glyphosate IPA mixed with Competitor. The present study indicates that the toxicity of a tank mix may be greatly increased by the addition of surfactants and may vary widely depending on the specific surfactant.

The Effect of Herbicide Formulations and Herbicide–Adjuvant Mixtures on Aquatic Food Web Species of the Sacramento–San Joaquin Delta, California, USA

“…Although data are lacking for comparable species, Smith et al (2004) investigated the toxicity of 4 surfactants to juvenile rainbow trout (Oncorhynchus mykiss) and found Agri-dex to be the least toxic (96-h LC50 271 mg/L) of those tested, compared to Hasten ® (74 mg/L), LI 700 ® (17 mg/L), and R-11 ® (6 mg/L). Vincent and Davidson (2015) compared the toxicity of glyphosate with and without surfactants to Anaxyrus boreas tadpoles and found the combination of glyphosate and adjuvant to be more toxic than glyphosate alone (48-h LC50 6392 mg/L). Again, Agri-dex was the least toxic of the adjuvants tested because the combination of glyphosate and Competitor ® (48-h LC50 711 mg/L) was up to 6 times more toxic than glyphosate and Agri-dex (48-h LC50 4254 mg/L; Vincent and Davidson 2015).…”

Hepato-morpholoy and biochemical studies on the liver of albino rats after exposure to glyphosate-Roundup®

“…GLP is used in commercial formulations, which include other chemical additives (including surfactant) that enhance its efficiency as a weed killer, by promoting toxicity and improving the plant's ability to take up the herbicide (Vincent andDavidson 2015 andDefarge et al 2016). It has a low permanence and because of employment of this herbicide for prevailing of weeds in agricultural fields, large quantities find their way into water bodies.…”

Towards Sustainable Environmental Quality: Priority Research Questions for the Australasian Region of Oceania

“…These "other" or "inert" ingredients have the potential to alter the environmental fate and toxicity of the active components in commercial formulations as well as in other contaminants and may also present their own inherent hazards and risks (Cox and Surgan 2006). For example, glyphosate formulations containing surfactants were more toxic than glyphosate on its own (Vincent and Davidson 2015). Such ingredients may not be listed, especially for proprietary formulations, making it difficult to identify and prioritize components of formulations for study.…”