The objective of this research was to evaluate the toxicity of the industial xenobiotic Aroclor 1248 (A) and natural origin substances~elemental sulfur (S80) and oleic acid (OA) and their binary mixtures to V. fischeri bioluminescence during the prolonged exposure time (up to 60 min). The bioluminescence quenching test was used to determine the toxic effects. Full factorial experiment design and multiple regression analysis and the comparison of binary mixture effect with the sum of effects of individual chemicals were used for the evaluation of combined effects of toxicants.
The analysis of general trend of mixture toxicity to bioluminescence showed that mixture toxic effects were reversible up to 60 min. Data analysis revealed different joint effects, which were depended on mixture composition. S80 enhanced toxic effect of A and acted additively with synergistic interaction. Hydrophobic OA in mixture with A acted antagonistically and in mixture with sulfur caused an additive effect with antagonistic component of interaction.
It was concluded that low concentrations of natural toxic substances present in environmental samples as mixtures of chemicals can define the toxicodynamic character of industrial xenobiotics.

Abstract
 1. Introduction
 2. Materials and Methods
  2.1. Materials
  2.2. Methods
 3. Results and Disccusion
  3.1. Trend of binary mixture toxicity
  3.2. Joint effects of Aroclor 1248, oleic acid andsulfur in binary mixtures
 4. Conclusions
 REFERENCE

• Virginija Kalciene(Centre for Ecology and Environmental Research, Faculty of Natural Sciences, Vilnius University) Corresponding author
• Daiva Dabkeviciene(Department of Biochemistry and Molecular Biology, Faculty of Natural Sciences, Vilnius University)
• Anolda Cetkauskaite(Department of Biochemistry and Molecular Biology, Faculty of Natural Sciences, Vilnius University)