Influence of natural radon and metal contamination on surface water quality from a Brazilian Semiarid Region / Influência da contaminação natural pelo radônio e metais na qualidade das águas superficiais da Região Semiárida Brasileira

The Brazilian semiarid region presents some adverse environmental conditions for the settled population such as a restricted water availability and the presence of radon and metal natural sources that can contaminate the water reservoirs and consequently become a concern for human health. The present study evaluated the water quality of the Riacho das Cachoeiras Dam located in the urban area of Lajes Pintadas (state of Rio Grande do Norte, Brazil) as source for human consumption. An analysis of Physicochemical parameters, heavy metal content and Radon in water samples was performed along with the assessment of the water mutagenic potential through Micronucleus Test (MN) on Tradescantia pallida and Oreochromis niloticus. The content of metals in water for Al, Cd, and Ni were above water quality guidelines for human consumption. Moreover, high levels of Pb along with dissolved Radon were found. An acute and chronic mutagenic water capability was observed. These findings demonstrated that the water quality is unsuitable for human consumption due to the presence of high levels of contaminants mainly from geogenic origin and its deleterious effect on living systems.

A região semiárida brasileira apresenta condições ambientais adversas para população local, como a escassez na disponibilidade de água e a presença de fontes naturais de radônio e de metais que podem contaminar os reservatórios de água e, consequentemente, tornar-se um problema de saúde humana. O estudo avaliou a qualidade da água do Açude do Riacho das Cachoeiras localizado na área urbana de Lajes Pintadas (Rio Grande do Norte, Brasil) como fonte para o consumo humano. Foram realizadas análises físico-químicas, de conteúdo de metais e de radônio em amostras de água em conjunto com a avaliação do potencial mutagênico da água por meio do teste de micronúcleos (MN) em Tradescantia pallida e Oreochromis niloticus. Os metais Al, Cd, e Ni estavam acima das diretrizes de qualidade da água para o consumo humano. Além disso, foram encontrados altos níveis de Pb dissolvido, juntamente com o radônio. Observou -se um potencial de indução de efeito mutagênico nas amostras de água testadas, tanto na exposição aguda quanto na crônica. Estes resultados demonstram que a qualidade da água do Açude está imprópria para o consumo humano devido à presença de elevados níveis de contaminantes de origem geogênica, com capacidade de exercer efeito deletério sobre os organismos.

Micronucleus study of the quality and mutagenicity of surface water from a semi-arid region.

The present study evaluated the mutagenic potential of surface water from the Lucrecia dam. The Tradescantia-micronucleus (Trad-MCN) test and CBMN assay in human peripheral blood lymphocytes were applied, corresponding to an in vivo and in vitro system, respectively. Heavy metals and some physicochemical properties were also measured. Water samples were collected in November 2009 (dry season) and May 2010 (rainy season) at three different points. Results of both assays for raw water showed positive responses for the points analyzed when compared to the negative control. The CBMN assay showed that diluted water was still able to induce a significant increase in micronucleus frequency. For both assays, the highest mean MN was observed in the dry season. Chemical analyses detected an increase in heavy metal levels at the sampling points and in the different seasons. These findings indicate the presence of genotoxins, such as heavy metals, in the water, which may be affecting the entire ecosystem, as well as human health. More prolonged monitoring is recommended in order to better characterize this public water supply.

Genotoxic analysis in aquatic environment under influence of cyanobacteria, metal and radioactivity.

The micronucleus (MN) and nuclear abnormality (NA) tests were employed to evaluate the genotoxic potential of the Lucrecia dam (RN, Brazil) located in a semi-arid region and influenced by crop irrigation and irregular rainfall. The analyses of these water samples demonstrated the presence of several cyanobacteria as well as metals and radioactivity. The Nile Tilapia (Oreochromis niloticus) was used for micronucleus and nuclear abnormality assays and analysis of metal concentrations in gills and liver samples. Genotoxic assays in source water fish showed a significant increase in the frequency of nuclear damage (MN and NA) in relation to the negative control group. In conclusion, the results obtained with water surface and biological samples from the Lucrecia dam suggest that this important water resource contains a number of chemical and microbiological pollutants with genotoxic potential and that these substances may be compromising the species inhabiting this ecosystem. Particular care must be taken to prevent further degradation of this water supply. Capsule: A battery of assay was successfully applied to assess the water quality of Lucrecia dam from a Northeastern region of Brazil.