Volta Redonda (RJ) - a cidade do aço: citogenotoxicidade da água do Rio Paraíba do Sul

Abstract

Volta Redonda, a city located in the state of Rio de Janeiro (Brazil), is considered one of the great industrial centers in the country. The city was strategically chosen to house CSN (Companhia Siderúrgica Nacional), one of the largest industries in the country. The city is nicknamed, then, as the city of steel. As a consequence of its industrial activity, Volta Redonda-RJ is one of the most polluted cities in Brazil, with aspects of soil, water and air pollution. In this work, we studied the cytogenotoxic effects of water samples collected in the Paraíba do Sul River. The reference point for the study was the existence of a mountain of solid industrial waste discarded by CSN, called steel slag, which is located in an area close to CSN. This waste is only 60m from the Paraíba do Sul River, probably a point of contamination in the river. Water samples were collected, then, at the entrance of the river in the city (P1), a little ahead of the slag mountain (P2) and at the exit of the river from the city (P3). Distilled water was used as a negative control treatment (NC). The treatments were evaluated for their cytogenotoxic potential through the assay on Allium cepa L., using cytogenetic technology and flow cytometry. Treatments were arranged in a completely randomized design consisting of three replications (three slides for cytogenetic analysis or 3 samples for analysis by flow cytometry). Cytogenetic analysis showed a significant reduction of MIs in all investigated treatments, except for P2 where the mitotic index increased in relation to NC (Dunnett, p<0.05). In this same treatment (P2) a significant increase in IPro was observed (Dunnett, p<0.05). In the present analysis, significant effects were observed for both clastogenic and aneugenic alterations, with a greater predominance of aneugenic alterations induced by water from the Paraíba do Sul river. In the case of this type of alteration, all treatments (P1, P2, P3) showed an increase in the percentage of its occurrence in relation to the NC (Dunnett, p<0.05). In treatments P2 and P3, the rate of this type of change is high and significant (Dunnett, p<0.05), mainly due to the occurrence of a alteration in the behavior of the mitotic spindle that leads to a type of genetic alteration called c-metaphase. This alteration showed a statistically significant increase in its percentage in treatments P2 and P3 (Dunnett, p<0.05). The increase in MI in P2 seems to be related, therefore, to both the increase in prophases and metaphases. Corroborating this effect, in the analysis by flow cytometry, there was an increase in the percentage of nuclei in G2/Prophase both in treatment P2 and in treatment P3. With regard to cell death indicators (Sub-G1, FSC, SSC, IFa and CV), treatments P2 and P3 were those that demonstrated an occurrence of cell death, but this effect does not seem to be very prominent. It is demonstrated in this pilot work that the water of the Paraíba do Sul River in Volta Redonda-RJ has cytogenotoxic effects, requiring a more comprehensive analysis of its effects.