Study of toxicity of pesticides using luminescent bacteria photobacterium phosphoreum

Abstract

The relative toxicity (expressed as 5-mm EC5O value - the concentration of chemical which reduces the light output of bacteria by 50% after contact for 5 minutes) of 13 pesticides (e.g., 2,4-dichiorophenoxyacetic acid, atrazine, coumarin, glyphosate, paraquat, pentachlorophenol, lindane, malathion) and 14 solvents was evaluated using Biotox™ test that is based on reconstituted freeze-dried viable Photobacterium phosphoreum. The most toxic of the 13 pesticides analyzed using Biotox™ was pentachlorophenol (5-mm EC5O=O.55 mg/L) and the less toxic was paraquat (5-mm EC5O=14800 mg/L). The 5-mis EC5O data for Biotox™ were compared to the respective data for Microtox™ test (also based on freeze-dried P. phosphoreum) and rodent oral LD5O values. For Biotox™ vs Microtox™ the log-log correlation coefficients for the whole data set (pesticides+ solvents, pesticides, solvents) were 0.78, 0.37 and 0.95, respectively. The less toxic solvents to Biotox™ were ethylene glycol, DMSO, methanol, ethanol, acetone and acetonitrile and, therefore, these solvents could be used for increasing the solubility of lipophilic compounds, e.g., for testing the toxicity of pesticides.In order to analyze toxic effects of pesticides in complex mixtures the EC5O values of pentachlorophenol, coumarin and glyphosate as pure substances and in their mixtures were compared: the toxic effects of the above-mentioned pesticides in their mixtures were not additive.