Environmental exposure tier-testing

Tier 2 PRA process involved developing environmental exposure data and chronic toxicity data distributions for individual POPs. The mean concentrations of POPs in local marine water measured at various locations were used as exposure data in the construction of the exposure distribution. The chronic toxicity data distribution was established based on published international acute toxicity data (LC50, EC50) on a variety of aquatic organisms tested in many jurisdictions, drawn primarily from the USEPA ECOTOX database (2002) (available at http //www.epa.gov/ ecotox). If the upper 5th centile of the measured chemical exposure data distribution did not exceed the lower 5th centile of its estimated chronic toxicity distribution, the potential ecological risk posed by the chemical was judged to be tolerable (Hall and Giddings, 2000). 

A tiered approach is used for pesticide exposure assessment at the surface water level. Depending on the results of the initial risk assessment, more extensive testing relative to the environmental exposure or hazard may be required to define the full environmental risk. The data are generated from such increasingly comprehensive series of studies (higher tiered studies). At each tier a comparison has to take place between the estimated exposure and... 

As indicated above, the nature and amount of data required for pesticide approval depend on the properties and use of each active substance. A stepwise, tiered or triggered approach allows an efficient selection of tests essential to each individual contamination risk analysis. The environmental exposure to a pesticide depends primarily on the following factors. 

In view of these complexities, environmental studies that seek to verify proposed cause-effect relationships between contamination and response need to be carefully designed to avoid bias and misunderstanding. Most environmental assessments adopt a multi-tiered approach to testing, in which combinations of biological responses (biomarkers) are measured in tissue samples, body fluids or at the whole organism level to indicate exposure to or adverse effects of contamination.8. Auffret and colleagues60 surveyed Pacific oysters from the Atlantic coast of Brittany after the Erika oil spill between... 

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