Toxicity assessment of the maize herbicides S-metolachlor, benoxacor, mesotrione and nicosulfuron, and their corresponding commercial formulations, alone and in mixtures, using the Microtox(®) test.
The Microtox(®) test, using the prokaryote Vibrio fischeri, was employed to assess the toxicity of the maize herbicides S-metolachlor, benoxacor, mesotrione and nicosulfuron, and their formulated compounds: Dual Gold Safeneur(®), Callisto(®) and Milagro(®); alone and in mixtures. For each compound we obtained original IC50 values, with consistent higher toxicities for formulated compounds compared to active ingredients alone. Mixtures of the four herbicides, prepared according to application doses encountered in agriculture, were found to be toxic at a lower concentration than single molecules. Mesotrione and nicosulfuron mixture appeared to be highly toxic to V. fischeri, however, this recommended post-emergence combination for maize crops got its toxicity decreased in formulated compound mixtures, suggesting that chemical interactions could potentially reduce the toxicity. Data comparisons to theoretical models showed a good prediction of mixture toxicity by Concentration Addition concept. Results seemed to exclude any synergistic effects on V. fischeri for the tested herbicide mixtures. Additional work coupling these bioassay data to ecosystemic level studies (aquatic and soil compartments) and data on additives and degradation products toxicity, will help to fill the gap in our knowledge of the environmental impact of these xenobiotics and in the choice of a more sustainable use of pesticides.
Clermont Université, Université Blaise Pascal, LMGE, F-63000 Clermont Ferrand, France; CNRS, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, F-63177 Aubière, France. Electronic address: pierre.joly@univ-bpclermont.fr.
Pierre
P
Joly
Frédérique
F
Bonnemoy
Jean-Christophe
JC
Charvy
Jacques
J
Bohatier
Clarisse
C
Mallet
D000081:Acetamides / Q000633:toxicity; D048908:Aliivibrio fischeri / Q000187:drug effects*; D003512:Cyclohexanones / Q000633:toxicity; D006540:Herbicides / Q000633:toxicity*; D010078:Oxazines / Q000633:toxicity; D011725:Pyridines / Q000633:toxicity; D013453:Sulfonylurea Compounds / Q000633:toxicity; D018675:Toxicity Tests; D003313:Zea mays
D000081:Acetamides; D003512:Cyclohexanones; D006540:Herbicides; D010078:Oxazines; D011725:Pyridines; D013453:Sulfonylurea Compounds; C432907:mesotrione; C416723:nicosulfuron; C085163:benoxacor; C051786:metolachlor
Formulated compounds; Herbicides mixtures; Microtox®; Toxicological study