Fractionation of Metals in Anaerobic Sediment Samples from Reconquista River and Assessment of its Biological Impact as Atmospheric Particles

FERRARO S., TASAT D., CURUTCHET G.

New Orleans

Congreso; SETAC North America 30th Annual Meeting held 16-20 November 2009; 2009

Reconquista River is one of the most polluted water courses in Argentina. It crosses heavily populated zones in San Martín city, presenting serious conflicts regarding its water and sediments quality. Its flooding plain remains dry on the low water seasons, and oxidation of both sulphur and organic matter present in the sediment noticeably raises the heavy metals bioavailability. In addition, particulate matter (PM) from the dry sediments moves to the atmosphere and deposits on the respiratory tract of people living on the Reconquista`s bank. The metal composition of Reconquista River PM (RRPM) and their bioavailability have been analyzed by fractionation using a BCR sequential extraction procedure. Fine particles (PM2.5) have been characterized morphologically by SEM, and its elemental composition by EDAX finding Chrome, Zinc and Lead levels higher than the imposed by the National Regulation of Dangerous Residues of Argentina (Law 831/93). We studied the biological effect of RRPM on the airways of healthy Balb/c mice (control group C), intranasally exposed to 10 μg/ml RRPM (group PM), sensibilised with ovalbumin 20 µg/ 2 mg Aluminum (group S) (emulating lung allergic inflammation) and intranasally sensibilized and exposed to RRPM 10 μg/ml (group S+PM) (n=6 per group). Previously, we suggested that variations in several metabolic parameters observed in exposed to RRPM groups were associated to the presence of heavy metals. RRPM rose the total cell number mainly the polymorphonuclear (PMN) population and augmented proinflammatory mediators levels (specifically IL-6) and the generation of reactive oxygen species (particularly O2-). In this work we studied the response of two key-role antioxidant enzymes, superoxide dismutase (SOD) activity and catalase (CAT) concentration, in animal lungs exposed to RPMM. We found that only SOD rose on the PM group. Antioxidant defense mechanism seems to better respond in exposed to RRPM animals than in sensibilized animals, where SOD activity was partially impaired falling by half even when compared to the control group. In addition we studied in the bronchoalveolar lavage cells obtained from exposed animals to RRPM, RRPM stripped of its metal bioavailable fraction (EDTA treatment) or to the bioavailable fraction alone, the occurrence of apoptosis. Apoptosis was evaluated by immunocytochemical (PARP and Caspase3) and histochemical (Hoechst) techniques. We observed that the metallic bioavailable fraction present in RRPM was the main responsible for the DNA damage. These results suggest that RRPM provokes adverse biological impact on the respiratory tract, which is largely aggravated in previously sensibilised animals.