2.3. Risk analysis
After determining the values for the median effect concentration (EC50)
and median lethal concentration (LC50), the results were compared with the
concentrations of residues for each pesticide, for the estimation of the
deterministic and probabilistic risk.
The deterministic risk analysis consisted of comparing the EC50 or LC50
values found in the toxicological tests performed in the laboratory with the
critical values obtained in the field. The coefficient of risk (CR), according to
the USEPA (1999), lists the maximum concentrations found in the
environment divided by the LC50 or EC50 values obtained in the tests. The risk
analysis criteria vary with the duration of the toxicity test, and for tests of
short duration (maximum of 96 h) the criteria are CR > 0.1 for situations of
risk mitigation, i.e. restriction of the use of the product, and CR > 0.5 for high
ecological risk. The values obtained for the residues were analyzed for each
river basin by adopting the maximum value recorded for a scenario of critical
contamination