Preliminary Study on the Toxicity of Some Anions Using Vibrio Fischeri as a Biological Target

Aim of the study is to establish dose-response curves for: nitrates (NO3), nitrites (NO2), sulphates (SO4), and fluorides (F-) in aqueous solutions. It appears that the Microtox test is sensitive enough to detect toxicity of some anions with respect to European Union (EU) official regulations dealing with pollution control.Microtox analysis was conducted as planned in ISO 11348–3:2007 for waste water analysis using anion standards Merck and Diluent SDI reagent. The anion solutions were prepared according to the limit of concentrations allowed in industrial waste water of the EU official regulations: NO3 20 mg/L, NO2 0.6 mg/L, SO4 1000 mg/L, and F- 6 mg/L; from this solution 3 dilutions were made: 3/4, 1/2, 1/4. Practically, the EC50 values were calculated by regression analysis of the linear relationship between the logarithm of the anions concentration against the logarithm of the lost/remaining light intensity ratio.All anions investigated result with toxicity <50% both at 5 to 15 minutes. As expected, NO3 and SO4 have a nourishing effect on Vibrio fischeri; NO2, and F instead have a constant effect in all dilutions. When the mix of all anions indagated was tested, at the same dilution, the toxicity resulting is less than the individual anion. This could be caused by many factors, such as the nutrient effect and to not mention physical factors.Our study underscores the difficulty to predict the resulting toxicity of a chemical mixture. Regarding adequate environmental safeguards, the single low limits of waste water cannot take account of the synergy effects caused by the different possible combination of the effluents composition. However, any possible synergistic enhancements in toxicity cannot be ignored.