The present study aimed to verify the genotoxic and citotoxic potential in water samples from the basin of Tapanhon River, Pindamonhangaba, São Paulo, by using the Allium test. Water samples of the Tapanhon River and its affluents (the Primeira Água and Segunda Água Streams, the Galega Brook) as well as a sample from the Borba Spring have been collected for negative control. Six bulbs of Allium cepa have been submitted to each of the samples for 24 hours. The roots have been fixed in ethanol/acetic acid 3:1; they have also been submitted to the Feulgen reaction, and the meristematic portion has been crushed in slide for cellular analysis. As such, 6000 cells have been collected for evaluation of the mitotic index (MI) and micronuclei (MNC) as well as 300 cells in the metaphase and anaphase phases, to evaluate chromosome aberrations (CA). No MNC has been found in the samples tested. The MI values have shown to be elevated in all samples tested when compared to the control with statistical relevance, however, only for the samples from the Primeira Água Stream and the Galega Brook (p<0,05). Chromosome aberrations have been observed in all samples (p<0,05). These data suggest that along this bay there are substances which induce the citotoxic and genotoxic effects, which, in turn, have promoted alterations in the organism tested. © 2006 Sociedade Brasileira de Toxicologia.2001/02/156572Antonsiewicz, D., Analysis of the cell cycle inn the root meristem of Allium cepa under the influence of Ledakrin (1990) Folia Histochem Cyto, 28, pp. 79-96Ateeq, B., Abul, F.M., Niamat, A.M., Ahmad, W., Clastogenicity of pentachlorophenol, 2,4-D and butachlor evaluated by Allium root tip test (2002) Mutation Research - Genetic Toxicology and Environmental Mutagenesis, 514 (1-2), pp. 105-113. , DOI 10.1016/S1383-5718(01)00327-8, PII S1383571801003278Cabrera, G.L., Rodriguez, D.M.G., Genotoxicity of leachates from a landfill using three bioassays (1999) Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 426 (2), pp. 207-210. , DOI 10.1016/S0027-5107(99)00069-X, PII S002751079900069XCabrera, G.L., Rodriguez, D.M.G., Maruri, A.B., Genotoxicity of the extracts from the compost of the organic and the total municipal garbage using three plant bioassays (1999) Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 426 (2), pp. 201-206. , DOI 10.1016/S0027-5107(99)00068-8, PII S0027510799000688Estação Primavera, , http//www.cptec.inpe.br/clima, Disponível em Acessado em 02 Abril. 2005Chandra, S., Chauhan, L.K.S., Murthy, R.C., Saxena, P.N., Pande, P.N., Gupta, S.K., Comparative biomonitoring of leachates from hazardous solid waste of two industries using Allium test (2005) Sc. Total Environ, 346, pp. 56-59(2005) Relatório de Qualidade Das Águas Interiores Do Estado de São Paulo 2004, p. 297. , Companhia de tecnologia de saneamento ambiental (CETESB). São Paulo, SP(2005) Guia de Coleta e Preservação de Amostras de Água, , Companhia de tecnologia de saneamento ambiental (CETESB). Comunicação pessoalDash, S., Panda, K.K., Panda, B.B., Biomonitoring of levels of mercurial derivaties in water and soil by Allium micronucleus assay (1988) Mutation Res, 203, pp. 11-21Egito, L.C.M., Medeiros, M.G., Medeiros, S.R.B., Agnes-Lima, L.F., Cytotoxic and genotoxic potential of surface water from the Pitimbu river, northeastern/RN Brazil (2007) Genetics and Molecular Biology, 30 (2), pp. 435-441. , http://www.scielo.br/pdf/gmb/v30n2/a23v30n2.pdfEvseeva, T.I., Geras'kin, S.A., Shuktomova, I.I., Genotoxicity and toxicity assay of water sampled from a radium production industry storage cell territory by means of Allium-test (2003) Journal of Environmental Radioactivity, 68 (3), pp. 235-248. , DOI 10.1016/S0265-931X(03)00054-7Fiskesjö, G., The Allium test in wastewarter monitoring (1993) Environ. Toxicol. Water, 8, pp. 291-298Fiskesjö, G., The Allium test - A alternative in environmental studies: The relative toxicity of metal ions (1988) Mutation Res, 197, pp. 243-260Fiskesjo, G., The Allium test as a standard in environmental monitoring (1985) Hereditas, 102 (1), pp. 99-112Grant, W.F., Chromossome aberration assays in Allium (1982) Mutation Res, 99, pp. 273-291Grant, W.F., Higher plant assays for the detection of chromosomal aberrations and gene mutations-a brief historical background on their use for screening and monitoring environmental chemicals (1999) Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 426 (2), pp. 107-112. , DOI 10.1016/S0027-5107(99)00050-0, PII S0027510799000500Grisolia, C.K., De Oliveira, A.B.B., Bonfim, H., Klautau-Guimaraes, M.N., Genotoxicity evaluation of domestic sewage in a municipal wastewater treatment plant (2005) Genetics and Molecular Biology, 28 (2), pp. 334-338. , http://www.scielo.br/pdf/gmb/v28n2/a26v28n2.pdfGrover, I.S., Kaur, S., Genotoxicity of wastewater samples from sewage and industrial effluent detected by the Allium root anaphase aberration and micronucleus assays (1999) Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 426 (2), pp. 183-188. , DOI 10.1016/S0027-5107(99)00065-2, PII S0027510799000652Koivusalo, M., Pukkala, E., Vartiainen, T., Jaakkola, J.J.K., Hakulinen, T., Drinking water chlorination and cancer - A historical cohort study in Finland (1997) Cancer Causes and Control, 8 (2), pp. 192-200. , DOI 10.1023/A:1018420229802Koivusalo, M., Jaakkola, J.J.K., Vartiainen, T., Hakulinen, T., Karjalainen, S., Pukkala, E., Tuomisto, J., Drinking water mutagenicity and gastrointestinal and urinary tract cancers: An ecological study in Finland (1994) American Journal of Public Health, 84 (8), pp. 1223-1228Liu, D., Jiang, W., Li, M., Effects of trivalent and hexavalent chromium on root growth and cell division of Allium cepa (1992) Hereditas, 117, pp. 23-29Ma, T., Xu, Z., Xu, C., McConnell, H., Rabago, E.V., Arreola, G.A., Zhang, H., The improved Allium/Vicia root tip micronucleus assay for clastogenicity of environmental pollutants (1995) Mutation Res, 334, pp. 185-195Marcano, L., Carruyo, I., Del, C.A., Montiel, X., Cytotoxicity and mode of action of maleic hydrazide in root tips of Allium cepa L. (2004) Environmental Research, 94 (2), pp. 221-226. , DOI 10.1016/S0013-9351(03)00121-XMarcano, L., Bracho, M., Montiel, X., Carruyo, I., Atencio, L., Efecto mitotóxico y genotóxico del cadmio en poblaciones meristemáticas de Allium cepa L. (cebolla) (1998) Ciência, 6, pp. 93-99Matsumoto, S.T., Mantovani, M.S., Malaguttii, M.I.A., Dias, A.L., Fonseca, I.C., Marin-Morales, M.A., Genotoxicity and mutagenicity of water contaminated with tannery effluents, as evaluated by the micronucleus test and comet assay using the fish Oreochromis niloticus and chromosome aberrations in onion root-tips (2006) Genet. Mol. Biol, 29, pp. 148-158Matsumoto, S.T., Marin-Morales, M.A., Mutagenic potential evaluation of the water of a river that receives tannery effluent using the Allium cepa test system (2004) Cytologia, 69 (4), pp. 399-408. , DOI 10.1508/cytologia.69.399Mello, M.L.S., Junqueira, A.C., Maria, C.C.J., Ribeiro, D.M., Ferreira, R.C., Veríssimo, R.V., Schildknecht, P.H.P.A., Silva, E.A., Monitoramento por ensaios biológicos de poluição ambiental no lago do parque ecológico Hermóneges Freitas Leitão Filho (1998 a 2004) (2004) I Congresso de Meio Ambiente Paulínia e Região Metropolitana de Campinas, 2004, Paulínia, pp. 1-8. , Anais - CD-Rom. Campinas: UNICAMPMello, M.L.S., Vidal, B.C., A reação de Feulgen (1978) Ciência e Cultura, 30, pp. 665-676Moraes, D.S.L., Jordão, B.Q., Degradação de recursos hídricos e seus efeitos sobre a saúde humana (2002) Rev Saúde Pública, 36 (3), pp. 370-374Nielsen, M.H., Rank, J., Screening of toxicity and genotoxicity in wastewater by the use of the Allium test (1994) Hereditas, 121, pp. 249-254Odeigah, P.G.C., Nurudeen, O., Amund, O.O., Genotoxicity of oil field wastewater in Nigeria (1997) Hereditas, 126 (2), pp. 161-167Ohe, T., Watanabe, T., Wakabayashi, K., Mutagens in surface waters: A review (2004) Mutation Research - Reviews in Mutation Research, 567 (2-3 SPEC. ISS.), pp. 109-149. , DOI 10.1016/j.mrrev.2004.08.003, PII S1383574204000602Palacio, S.M., Espinoza-Quinones, F.R., Galante, R.M., Zenatti, D.C., Seolatto, A.A., Lorenz, E.K., Zacarkim, C.E., Tabacniks, M.H., Correlation between heavy metal ions (copper, zinc, lead) concentrations and root length of Allium cepa L. in polluted river water (2005) Brazilian Archives of Biology and Technology, 48 (SPEC. ISS.), pp. 191-196Dados Gerais Sobre Pindamonhangaba, , http://www.pindavale.com.br/acidade/dadosgerais.asp, Disponível em Acessado em 31 Mar. 2005Quiblier, C., Leboulanger, C., Sane, S., Dufour, P., Phytoplankton growth control and risk of cyanobacterial blooms in the lower Senegal River delta region (2008) Water Research, 42 (4-5), pp. 1023-1034. , DOI 10.1016/j.watres.2007.09.030, PII S0043135407006264Rank, J., Nielsen, M.H., Genotoxicity testing of wastewater sludge using the Allium cepa anaphase-telophase chromosome aberration assay (1998) Mutation Research - Genetic Toxicology and Environmental Mutagenesis, 418 (2-3), pp. 113-119. , DOI 10.1016/S1383-5718(98)00118-1, PII S1383571898001181Sua Região, , http://www.sabesp.com.br, Disponível em Acessado em 21 Mar. 2005Smaka-Kincl, V., Stegnar, P., Lovka, M., Toman, M.J., The evaluation of waste, surface and ground water quality using the Allium test procedure (1996) Mutation Research - Genetic Toxicology, 368 (3-4), pp. 171-179. , DOI 10.1016/S0165-1218(96)90059-2Umbuzeiro, G.A., Roubicek, D.A., Sanchez, P.S., Sato, M.I.Z., The Salmonella mutagenicity assay in a surface water quality monitoring program based on a 20 year survey (2001) Mutation Res, 491, pp. 1190-2001Geografia Do Vale - Clima, , http://www.valedoparaiba.com/geografiadovale/clima.asp, Valedoparaiba.com. Disponível em Acessado em 25 Mar. 2005Villanueva, C., Kogevinas, M., Grimalt, J., Chlorination of drinking water in Spain and bladder cancer (2001) Gac Sanit, 15 (1), pp. 48-53Wang, B., Cultural eutrophication in the Changjiang (Yangtze River) plume: History and perspective (2006) Estuarine, Coastal and Shelf Science, 69 (3-4), pp. 471-477. , DOI 10.1016/j.ecss.2006.05.010, PII S0272771406001880