Toxicity Ranking and Toxic Mode of Action Evaluation of Commonly Used Agricultural Adjuvants on the Basis of Bacterial Gene Expression Profiles

Abstract

The omnipresent group of pesticide adjuvants are often referred to as “inert” ingredients, a rather misleading term since consumers associate this term with “safe”. The upcoming new EU regulation concerning the introduction of plant protection products on the market (EC1107/2009) includes for the first time the demand for information on the possible negative effects of not only the active ingredients but also the used adjuvants. This new regulation requires basic toxicological information that allows decisions on the use/ban or preference of use of available adjuvants. In this study we obtained toxicological relevant information through a multiple endpoint reporter assay for a broad selection of commonly used adjuvants including several solvents (e.g. isophorone) and non-ionic surfactants (e.g. ethoxylated alcohols). The used assay allows the toxicity screening in a mechanistic way, with direct measurement of specific toxicological responses (e.g. oxidative stress, DNA damage, membrane damage and general cell lesions). The results show that the selected solvents are less toxic than the surfactants, suggesting that solvents may have a preference of use, but further research on more compounds is needed to confirm this observation. The gene expression profiles of the selected surfactants reveal that a phenol (ethoxylated tristyrylphenol) and an organosilicone surfactant (ethoxylated trisiloxane) show little or no inductions at EC20 concentrations, making them preferred surfactants for use in different applications. The organosilicone surfactant shows little or no toxicity and good adjuvant properties. However, this study also illustrates possible genotoxicity (induction of the bacterial SOS response) for several surfactants (POEA, AE, tri-EO, EO FA and EO NP) and one solvent (gamma-butyrolactone). Although the number of compounds that were evaluated is rather limited (13), the results show that the used reporter assay is a promising tool to rank commonly used agricultural adjuvants based on toxicity and toxic mode of action data.

Effects-Directed Analysis of Dissolved Organic Compounds in Oil Sands Process-Affected Water

“…The steep dose−response curve of acute lethality caused by F3-NE2a is similar to that caused by surfactant-like compounds that act via a narcosis mode of action. 43,44 Because NAs are surfactants, it has been suggested that narcosis is the mode of acute toxicity of OSPW. 43,45 Acute toxicity of fractions from the esterifiable and acid-extractable fraction of OSPW also displayed a steep dose−response, similar to characteristics of surfactants.…”

How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate-based herbicides?

“…Most of the surfactants used in the formulation of GBHs are designed to accelerate the movement of glyphosate across plant surface membranes and also foster the movement of glyphosate into mammalian cells [31,35]. Many co-formulants are more toxic than technical glyphosate [31,36] and synergistic activity may occur in some exposure scenarios with certain formulations. Accordingly, differential toxicity arises from variable combinations of the innate toxicity of the surfactant(s) in a GBH compared to technical glyphosate, the impact of the surfactant(s) on the movement of glyphosate through human skin and into cells, and possible synergistic impacts [30,[37][38][39].…”

Genome-Wide Transcriptional Profiling and Metabolic Analysis Uncover Multiple Molecular Responses of the Grass Species Lolium perenne Under Low-Intensity Xenobiotic Stress

“…Such mechanisms are often studied under conditions of high exposures corresponding to application levels in the field. High levels of xenobiotics strongly impact organism physiology and defense responses, by inducing molecular injury and damages (Teixeira et al, 2007 ; Ramel et al, 2009 ; Das et al, 2010 ; Nobels et al, 2011 ; Gomes et al, 2014 ), mainly related to oxidative stress, membrane disruption, lipid peroxidation, protein damage, or DNA damage. In contrast, few studies deal with the responses to conditions of low exposure to pesticides in a context of runoff or residual contaminations.…”