WATER QUALITY IN THE BUENOS AIRES URBAN ECOSYSTEM

JORGE HERKOVITS, CRISTINA SILVIA PÉREZ-COLL AND LUIS CASTAÑAGA

Sao Paulo, Brasil

Congreso; IX Congresso Brasileiro de Ecotoxicologia; 2006

ECOTOX Brasil

  There is a well-accepted direct link between water quality and environmental and human health. In developing countries urban ecosystems are often heavily polluted and most rivers and streams are highly loaded with urban and industrial wastes.   By means of AMPHITOX, a versatile toxicity test with amphibian embryos, customized to acute, short-term chronic and chronic exposure periods, the toxicity of samples from rivers and streams in the metropolitan area of Buenos Aires were evaluated. By plotting the LC10 (or NOEC), LC50 and LC90 (or LC100), the toxicity profile (TOP) curves from 24 hr to 14 days of exposure were obtained allowing the visualization of concentration- and time-exposure thresholds, as well as the range of concentrations that exerts adverse effects in each case. Malformations were also evaluated in certain environmental scenarios. Because toxicity involves an inverse relationship to effective concentration (EC; the lower the EC the higher the toxicity) it is helpful to translate concentrations-based toxicity measurements into toxic units. The number of toxic units was defined as 100 divided by the EC measured: in the case of acute toxicity  (TUa)  100/LC50;  for chronic toxicity (TUc) 100/no-observed effect level. For whole industrial effluent, US EPA recommended a maximal value of 0.3 TUa and 1.0 TUc for the most sensitive of at least three test species in both case. These values were used as references for all the sample stations studied in the Buenos Aires region of Rio Reconquista and Rio Matanza-Riachuelo two major basins within the metropolitan area of Buenos Aires as well as minor basins like Las Conchitas stream. The water sampled was up to 20 times more toxic than the maximal value allowed by the US EPA for industrial effluents. In many places close by those heavily polluted rivers and streams poor populations is living precariously.  It seems that they are not fully aware on the adverse health effects of the contamination as in some cases children even play in heavily polluted water. People living a bit retired from those places consider themselves safe from water (and sediment) pollution.  No data on toxicity are available except a few scientific publications usually far away from public knowledge. Our proposal is to report and discuss by means of workshops at school level, priority issues related to the value of the water quality for the ecosystem services, biodiversity and human health. Within each workshop by means of a simple bioassay conducted in situ e.g. with amphibian embryos could illustrate the adverse effects of any pollutant (e.g. including chlorine in drinking water) on living organisms. In our view these actions could contribute to increase the awareness as well as the stewardship toward a better life quality in urban ecosystems. A copy of our activities will be provided to industry chambers, municipalities, and NGOs.