The focal point of this project is mixture effects caused by pesticides, and in particular mixture effects of mixtures in which pesticide adjuvants (co-formulants) is a part. As a first step, the project examines how the current European (EU) pesticide legislation and the consequent ecological risk assessment applied in the Nordic approval-zone relate to mixture effects of mixtures where co-formulants is a part. It is concluded that the ecological risk assessment performed during the approval of pesticide formulations in accordance to the relevant legislation, to a wide extent does take into account the contribution of co-formulants to the toxicity of pesticide formulations. Requirements of ecotoxicological examination of mandatory tank mixes (i.e. mixtures of pesticides formulations or the addition of pesticide adjuvants, according to the label required for optimum effect) are also included in the legislation. However, there are no test requirements for mixtures of pesticide formulations applied to the field, solely in order to reduce the number of applications (i.e. non-mandatory tank mixtures), or to mixtures of pesticide formulations generated by sequential field application. Since there are no tests requirements for non-mandatory tank mixtures, which is the most frequently used application method of pesticides, or for sequential mixtures, there is good reason to believe that there occurs mixture effects that are not taken into account, neither in the current European pesticides legislation nor in the Nordic ecological risk assessment. Hence, it was suggested that inclusion of risk assessment of these non-mandatory mixtures could improve the European pesticides legislation. In addition to the legislative and regulatory analysis, the toxic mixture effects of the active ingredient of the widely used RoundUp herbicde, glyphosate, and the co-formulant, POEA, to the ordinary yellow onion, Allium cepa, was examined in a root growth inhibition assay and by applying the use of a "fixed-ratio" study design. The experiment is performed in five mixture ratios (1: 0, 1: 0.2, 1: 0.6, 1: 1.9, and 0: 1 (glyphosate: POEA concentration ratio)). Mixture effects were assessed in relation to the concentration addition (CA) and independent action (IA) models. The observed mixing effects were characterized as being Bliss antagonistic, both at high (EC50-level) and low (EC10-level) concentrations and Loewe additive at high concentrations and weak Loewe antagonistic at low concentrations. It was found that CA, despite the fact that glyphosate and POEA has a fundamentally different toxic mode of action, would be a useful prediction model to assess the mixture effects of glyphosate and POEA and probably also other mixtures of active substances and co-formulants.
|Uddannelser||Miljøbiologi, (Bachelor/kandidatuddannelse) KandidatTekSam - miljøplanlægning, (Bachelor/kandidatuddannelse) Kandidat|
|Udgivelsesdato||30 apr. 2015|
|Vejledere||Gary Thomas Banta & Kristian Syberg|
- mixture toxicity
- Allium assay
- Pesticide regulation