Validation of EQS in the Field

Environmental and Human Health Standards for Water and Soil 

The USEPA has also validated freshwater EQS approaches (10 compounds to show proof of principle). It deploys this validation approach each time a new method (e.g., aquatic guidelines or sediment guidelines methodology) is being developed but not for every occasion when deriving a specific substance EQS. The United States addresses bioavailability in this approach (USEPA 1986). 

The goal of the validations is to ensure that concentrations at or below the EQS will not cause an adverse effect. The EQS therefore indicates the concentration below which an unacceptable adverse effect is unlikely to occur. Concentrations above the EQS may or may not cause effects depending on both the magnitude and frequency of the exceedance. In the USEPA approach, as in the aquatic life water quality criteria approach, newly generated data exceeding the standard (for that matter, all newly generated data of acceptable quality) will not replace this standard but will be added to the database from which data for estimating the standard are taken. 

Similar validation is conducted by some other regulatory authorities. For example, it was shown in an Australian study that there was no effect on sensitive species at concentrations 10 times above the EQS values for metals in sediments because of the EQS derivation method in which toxicity was equally ascribed to cooccurring chemicals (leading to concerns over the ecological realism of sediment metal EQS values) (Simpson et al. 2005). In Canada, no formal validation programs of this type have been undertaken. 

In summary, we are in favor of validating EQSs by inspecting field data. 

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