Environmental toxicology the background for risk assessment

Marco Vighi, Richard Lloyd and Carolina Sbriscia Fioretti 

The potential harmfulness of a chemical in the environment depends on several major properties toxicity to organisms, bioaccumulation in tissues, persistence, mobility and distribution patterns in environmental compartments. Historically, the focus of ecotoxicology was on the first property, toxicity, and techniques were devised to enable maximum concentrations of no harmful effect to be established, usually using responses measured in whole organisms. These concentrations then formed the basis of environmental quality standards. 

Considerable attention was focused on organismal effects at the cellular or subceUular level, where they first become apparent. These were often foimd at exposure concentrations lower than those predicted to be safe from tests on whole organisms. The ensuing scientific and political debate served only to cloud the validity of existing environmental quality standards, and indeed shed doubt on the value of ecotoxicological data in pollution prevention and control. 

At the same time, the definition of pollution was changing. The original definition (Uoyd, 1991) referred to damage caused to environmental 

To some extent, this change in definition followed from the development of extremely sensitive methods of chemical analysis. These enabled very low concentrations of chemicals to be measured in environmental compartments where they had previously been presumed to be absent. This fed a general concern that pollution was becoming more widespread the fact that these minute quantities were likely to cause no harmful effects to human beings or other organisms was overridden by a public perception that truly safe concentrations of these chemicals could not be established. 

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