To compare the toxicity of samples collected at the different stages of the SBR cycles, two types of assays were used with the eukaryotic model S. cerevisiae. The microplate susceptibility assay measured their inhibitory effects on yeast growth as an indication of potential cytotoxicity [15]. The gene expression assay [16] measured modifications on the transcription of the yeast genesGRE2 (related with general response to stress) [20] and RAD54and RNR3 (both related with specific responses to DNA damage)[17,21] caused by the samples, where increases in gene expression indicate potential cytotoxicity/oxidative stress and genotoxicity,respectively.