RESUMO
In this study, the onion (Allium cepa) root test was used to evaluate the genotoxicity of the Pitimbu River (Natal city, Brazil) surface water. The water was collected at five sampling sites along the river and one sample was obtained after the treatment (flocculation, chlorination and pH correction) of the river water for human consumption. All raw river water samples increased the frequency of chromosomal abnormalities and/or micronuclei and two of the water samples produced alterations in the mitotic index of the root cells. Two of the water samples also altered root growth and two produced morphological modifications in the A. cepa roots. Water collected from a site near an industrial area was the most consistently toxic and genotoxic of the samples. Although the water chlorinated for human consumption was not genotoxic, the data indicate that surface water from the Pitimbu River contains toxic and genotoxic compounds that potentially may impact this aquatic ecosystem.