SETAC Globe - Environmental Quality Through Science
  15 March 2012
Volume 13 Issue 3

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EXCESS: A New SETAC Advisory Group on the Effects of Extreme Stress on Ecosystems and Subsequent Recovery

Frederik De Laender, Ghent University

The chemical risk assessment procedures imposed by regulatory bodies require the derivation of chemical concentrations that can be used as a basis for setting environmental quality standards. In the European risk assessment framework, such a concentration is called a "predicted no effect concentration" (PNEC)(1). To quantify risk, this PNEC is compared to a predicted environmental concentration (PEC) in a risk quotient (RQ = PEC/PNEC). In response to this requirement by regulatory bodies, the ecotoxicological research community is—and has been—very active in examining the toxicity of the relatively low concentrations one expects in the environment. Likewise, many existing SETAC advisory groups use the regulatory risk assessment procedure as a framework.

An accurate risk assessment safeguards the environment from undesired effects from the daily production and use patterns of chemicals. However, chemical production and use may occasionally lead to the accidental exposure to elevated chemical concentrations. Such accidents may expose the environment to concentrations that by far exceed the PNEC, resulting in an unknown degree of unwanted effects on the exposed ecosystem(s). Although the probability of such accidents to occur is low, the resulting effects are potentially high, making the associated risks non-negligible. Note that here, risk is defined as probability ∙ effect and is therefore not the same as the RQ-based risk (RQ = PEC/PNEC).

Depending on the chemical type and the accident’s spatial and temporal scale, exposure concentrations may gradually decrease to the concentrations before the accident, either because the chemical is lost from the environment (e.g., microbial degradation) or because of remediation efforts. During this period, both recovery as well as delayed effects may occur. The rates of these processes are co-determined by intra- and inter-specific interactions showing that knowledge about such interactions is needed to predict ecosystem effects and subsequent recovery (2).

Currently, no SETAC AGs exist that focus on ecosystem-level effects and subsequent recovery following large-scale accidental exposure to high chemical concentrations. With this effort, we aim to assemble the expertise available within SETAC into an advisory group (AG). We argue that streamlining the available expertise on this matter is necessary, as the heterogeneity in the available data and scientific opinions does not contribute to consistent ecosystem effect assessments. In addition, this uncertainty makes it difficult to propose suitable remediation actions, as experienced with the Deepwater Horizon oil spill (3), and often leads to ambiguous communication to the public regarding the actual environmental effects of an extreme stress event, as was the case with the Ajka alumina plant accident (4). This demonstrates that assembling the available expertise on ecosystem-level effects is needed to synthesise the available knowledge into scientifically defensible assessments in a fast and efficient way in case extreme stress events occur.

In conclusion, we feel that this new AG is a timely and much needed initiative that has the potential to enhance the synergy within the SETAC community so that new knowledge will be produced that can be used by environmental managers and other scientists. That said, we encourage all interested parties, regardless of their methodological background (e.g., statistical and mechanistic modelling, biological and chemical monitoring techniques, micro- and mesocosm testing) to join us in this effort to better understand how ecosystems respond to and recover from extreme stress events.

References cited

  1. ECHA REACH: Guidance on Registration. ECHA-11-G-03-EN; Helsinki, Finland, 2011.
  2. Fleeger, J. W.; K. R. Carman, et al. Indirect Effects of Contaminants in Aquatic Ecosystems. Science of the Total Environment 2003, 317, (1-3), 207-233.
  3. Kerr, R.; Kintisch, E.; Stokstad, E., Gulf Oil Spill: Will Deepwater Horizon Set a New Standard for Catastrophe? Science 2010, 328, (5979), 674-675.
  4. Rosenthal, E., Hungary’s Red Sludge Spill: The Media and the Eco-Disaster. Yale Environment ( 2010, 360).

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