title: Assessing single and joint toxicity of three phenylurea herbicides using Lemna minor and Vibrio fischeri bioassays.
abstract: Single and joint toxicity of three substituted urea herbicides, namely monolinuron [3-(4-chlorophenyl)-1-methoxy-1-methylurea], linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and diuron [1-(3,4 dichlorophenyl)-3,3 dimethyl urea], were studied. The duckweed Lemna minor and the luminescent bacterium Vibrio fischeri were used for the toxicity assessment and they were exposed to various concentrations of the herbicides, individually and in binary mixtures. The exposure time was 7d for the duckweed and 30 min for the bacterium. Estimation of EC50 values was performed by frond counting and reduction in light output for Lemna minor and Vibrio fischeri, respectively. Lemna minor was found to be much more sensitive than Vibrio fischeri to target compounds. The toxicity of the three herbicides applied solely was estimated to be in decreasing order: diuron (EC50=28.3 μg L(-1))≈linuron (EC50=30.5 μg L(-1))>monolinuron (EC50=300 μg L(-1)) for the duckweed and linuron (EC50=8.2 mg L(-1))>diuron (EC50=9.2 mg L(-1))>monolinuron (EC50=11.2 mg L(-1)) for the bacterium. Based on the environmental concentrations reported in the literature and EC50 values obtained from Lemna minor experiments, Risk Quotients (RQ) much higher than 1 were calculated for diuron and linuron. In Lemna minor experiments, combination of target compounds resulted to additive effects due to their same mode of phenylurea action on photosynthetic organisms. Regarding Vibrio fischeri, synergistic, additive and antagonistic effects were observed, which varied according to the concentrations of target compounds.
authors.affiliation: Water and Air Quality Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece. Electronic address: ggatid@env.aegean.gr.
authors.forename: Georgia
authors.initials: G
authors.lastname: Gatidou
authors.affiliation: Water and Air Quality Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece.
authors.forename: Athanasios S
authors.initials: AS
authors.lastname: Stasinakis
authors.affiliation: Water and Air Quality Laboratory, Department of Environment, University of the Aegean, University Hill, 81100 Mytilene, Greece.
authors.forename: Evangelia I
authors.initials: EI
authors.lastname: Iatrou
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects* / Q000378:metabolism; D029064:Araceae / Q000187:drug effects* / Q000502:physiology; D001681:Biological Assay; D004237:Diuron / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity*; D008044:Linuron / Q000031:analogs & derivatives* / Q000633:toxicity; D049449:Luminescence; D010788:Photosynthesis / Q000187:drug effects; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D008044:Linuron; C030651:monolinuron; D004237:Diuron
keywords: Additivity; Combined toxicity; Effects; Risk assessment; Water