Derivation of environmental quality standards for biota using reliable bioaccumulation data
Abstract
The Water Framework Directive (2000/60/EC), or WFD, sets the strategy against the chemical pollution of surface water bodies. The evaluation of the chemical status allows parallel with the evaluation of the ecological status, to determine the overall quality of a water body. The environmental quality standards (EQS) are tools used to assess the chemical status of water bodies. Daughter directive (2013/39/EU) considers that EQS must be established in the matrix of the aquatic environment (water, sediment or biota) where a substance is likely to be found and where its concentration is most likely to be measurable. Some substances pose a significant risk through indirect toxicity (i.e. secondary poisoning resulting from food-chain transfer) and their analysis is more feasible in other environmental matrices, such as biota, then a biota standard may be required alongside, or instead of, the water column EQS. This work aims to derive quality standards applicable in biota equivalent to EQS for four dangerous and priority classified substances by the WFD (tributyltin, diethylhexylphthalate, short chains chloralkanes (C10-13) and pentachlorobenzene). Quality standards were derived using bioaccumulation factors. All retrieved literature was evaluated with respect to its relevance and reliability according to the TGD-EQS. Composition and completeness of the marine and freshwater food-chains are evaluated and only reliable and relevant data are considered valid for use in setting a quality standard. According to the matrix of the EQS, the principle of this deriving approach is based on: a conversion of the EQS from water to biota using bioaccumulation factors for each trophic level, or a conversion between different trophic levels (biota) directly by using the biomagnification factor if the substance is biomagnified, or by performing an intermediate conversion into the water if the substance is not biomagnified. Based on this principle, a general methodology for biota standards derivation is proposed. It seeks to determine, using a decision diagram, the best approach to convert a biota standard taking into account the availability of reliable bioaccumulation data. This methodology for deriving biota standards need to be validated for other substances in the context of monitoring of aquatic environments.