An approach to assess the regulatory relevance of micro-evolutionary effects in ecological risk assessment of chemicals

An approach to assess the regulatory relevance of micro-evolutionary effects in ecological risk assessment of chemicals: A case-study with Cd

etc thumb medium121 159Through ecological risk assessment (ERA) policy makers try to set protective norms for harmful chemicals in the environment. Typically, such ERAs are based on ecotoxicological research performed in the lab. However, these laboratory conditions tend to lack some measure of realism compared to the actual situation in the environment. For instance, usually only one particular individual of a species is considered in ecotoxicological tests, while in the environment multiple, different individuals are present. As with us, humans, some of these individuals can cope better with a certain chemical in the environment than others. Under continuous presence of such a chemical these, more tolerant, individuals will survive and reproduce, while the other individuals will perish. Overall, the group of individuals will become more tolerant to the chemical, a process which is called micro-evolution. In this most recent paper an approach is suggested to take this micro-evolutionary processes into account in ERA to, ultimately, make our risk assessment of chemicals in the environment more realistic.

 

Scientific abstract

The authors suggest an approach to assess the regulatory relevance of microevolutionary effects of chemicals based on a comparison of concentrations at which microevolutionary effects have been reported in the literature and conventionally derived ecotoxicological threshold concentrations. The authors found reports of microevolutionary effects of cadmium in freshwater organisms at hardness-normalized concentrations between 0.5 µg Cd L−1 and 6290 µg Cd L−1 (normalized to a hardness of 50 mg CaCO3 L−1). These concentrations were at least 1.5 times higher than the hardness-normalized hazardous concentration for 5% of the organisms of 0.34 µg Cd L−1. This suggests that there is no immediate need to consider microevolutionary effects of Cd in environmental risk assessments of freshwater environments. However, some other aspects should be kept in mind as well. First, microevolutionary effects have so far only been investigated at few, relatively high concentrations of Cd and not encompassing the 5% hazardous concentration. Second, different types of microevolutionary effects or investigated ecotoxicological end points may influence the conclusions of the suggested comparative approach. Finally, factors influencing the bioavailability of Cd were not commonly reported in the literature, which made normalization of concentrations at which evolutionary effects occurred impossible and affected the number of studies that could be evaluated in the suggested approach.

 

Full reference

De Coninck D, Janssen C, De Schamphelaere K. 2014. An approach to assess the regulatory relevance of micro-evolutionary effects in ecological risk assessment of chemicals: A case-study with Cd. Environmental Toxicology and Chemistry 33(2), 453-457. DOI: 10.1002/etc.2434

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