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Cristais River, located in the metropolitan region of São Paulo city, is used as source of drinking water and mutagenic activity was observed in the extracts obtained from its waters. This effect was associated to a discharge of a textile dye processing plant that contains, among other mutagenic compounds, the dyes C.I. Disperse Blue 373, C.I. Disperse Violet 93 and C.I. Disperse Orange 37. The objective of this work was to assess the mutagenic activity using the blue rayon hanging technique (BR)/Salmonella microsome assay and the Tradescantia-MCN mutagenicity test exposed in the fieldfor 24 hours before and after the discharge of the cited industrial effluent. The BR/Salmonella microsome assay showed to be sensitive to detect the mutagenicity, after the textile dye processing plant discharge. The Trad-MCN assay, using plant cuttings exposed directly in the river showed an increased response after the industrial discharge. Due to its simplicity and low cost, the Trad-MCN assay seems to be a good alternative for screening surface waters for mutagenic activity. Both techniques have the advantage of better represent the environmental conditions because the extraction/exposure is performed in the field during 24 hours.

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Organic extracts of raw water from 11 water courses of SLo Paulo State, Brazil, were collected during one year bimonthly and tested for mutagenicity using the Ames test, with strains TA98 and TAlOO of Salmonella typhimurium with and without metabolic activation. The samples were extracted with XADz resin and eluted with methanol and methylene chloride. From the 75 samples analyzed, 14 showed positive responses and 8 were considered marginal, making up 29% of mutagenic samples. The percentage of mutagenic samples in October (spring) was 9%, increasing to 64% in February (summer), and decreased to 9% again in August (winter). Paraiba do Sul river showed the higher percentage of mutagenic samples (67%) and Capivari river the highest mutagenic sample (1787 and 3265 revertants per liter for TA98 without and with S9, respectively).The amplitude of the mutagenic response was 39-3265 revertants per liter for TA98 and 83-467 for TA100. The mutagenic samples showed direct and indirect mutagens, and TA98 detected the majority of responses, indicating prevalence of frameshift mutagens in these samples. 0