Water quality criteria: application of a procedural approach of numeric criteria and risk assessment protocols to regulated toxicant concentrations in the aquatic environment

RESUMO

The purpose of this study is to discuss the adequacy of developing water quality criteria based on site/region specific conditions in place of using general legal standards to protect human health from the impacts of pollutants in aquatic systems. Human noncarcinogenic criteria (HNC) were developed for Zn, Mn, Ni, Hg, As and Cd and compared with legal standards adopted in Brazil and the US. Uncertainty analyses were carried ou to provide a quantitative estimate of the variation range of HNC model outputs. Finally a risk assessment based on a scenario of Hg pollution in a river in the Amazon basin was carried out. It has been found that with the exception of As and Cd, the Brazilian legal standar values are more restrictive than the HNC values. It is pointed out that the HNC equation is only based on the protection of human health and thus, it does not consider the protection of aquatic life. The risk assessment concerning Hg contamination suggested that the local riverine population is exposed to due Hg concentrations and adverse health effects are likely to occur.