This Task Group has a long history. It is coming forth from the Task Group launched during the IUR-SETAC Meeting on the Application of Radioecology to Other Contaminants (AROC), held in Antwerp (Belgium), February 2002. The aim was to bring together experts involved in experimental research and model development in closely related areas of environmental chemistry and toxicology. Pollution science combines a multitude of highly specialised disciplines and the Task Group attempts to bridge the gap between radioecology and other areas of environmental contamination and toxicology through identification of synergies.
In 2010, an agreement was signed between IUR and IAEA on the "Practical Arrangements for the exchange and dissemination of information within the IAEA-EMRAS II project, Working Group 6 on Biota dose effects modeling - Multiple Stressors." For the duration of the EMRAS-II programme (2009-2012), the short-term objectives given below do coincide.
Contaminants never occur in isolation. Increasing industrialisation and population density have led to the situations where mankind and its environment are exposed to a multitude of factors of which very often little is known about their mid- and long-term health and ecological consequences. Legislation is still mainly based on effects of single compounds, but in real life there is 'no such thing as a single chemical exposure'. The examination of combined low-dose chronic exposures, which corresponds much more realistically to exposure conditions in the environment than the analysis of single substances, entails major methodological difficulties in the experimentation and evaluation procedure. However, the potential risk of combined exposures makes the analysis of this topic area a high-priority issue.
More and more data become available that suggest that compounds can exert effects in mixture in concentration ranges in which the single contaminants do not show effects. Because it is impossible to experimentally assess the effect of all possible mixtures for all species and exposure conditions we need tools to make extrapolations and to understand effects of mixtures.
It is internationally recognised that there are severe gaps in basic knowledge with respect to the biological responses to multiple stressor exposures. Approaches, methodologies and tools are to be developed or improved to adequately assess the impact of multiple stressor conditions at the exposure, effects and global risk assessment levels. For conventional contaminants, the issue of multiple contaminants has been addressed in a number of international projects (e.g. NoMiracle, BEAM, MIXTOX, PHIME).
Dealing with risk assessment under multiple stressor or mixed contaminant exposure conditions is a major challenge. Determining mixture effects is a complex issue as co-contaminants may interact at different levels. Co-contaminants may affect the mobility, absorption, distribution, storage, biotransformation and elimination of the contaminants of interest. Toxic effects may show unexpected patterns in time and different endpoints of the same organism can show entirely different patterns of effects in time. To fully understand the effects of multiple stressors or mixed contaminant exposure conditions on life-history responses such as growth, reproduction and survival requires challenging experimentation and a multidisciplinary approach for understanding the mechanisms and processes producing the observed effects. It requires more complex methodological and computational tools than those applied in current risk assessment practices. The subject can only be dealt with through an integrated methodological approach with shared common goals and resources of an allied multidisciplinary international consortium.
Very few studies have considered the behaviour and effects induced by natural or artificial radionuclides in a representative multi-stressor context. However there are many examples where radiocontaminants occur in association with other contaminants and where assessment of the (combined) effect on the environment could be an issue. Discharges from the nuclear industry (particularly uranium mining and milling and reprocessing) and contamination following extraction and processing NORM are but a few of the potential exposure conditions.
Building a radioprotection system that takes into account the risks of radionuclides on organisms in a heterogeneous, dynamic and multipollution context, implies that we should make the addition of radiological effects compatible with other contaminants and develop a methodology for identifying when, where and how synergetic/antagonistic effects need to be addressed. These developments will need to be integrated in radiation protection guidelines.
Recently, environmental protection criteria for ionizing radiations have been derived by a number of international and national organisations (IAEA, ICRP, UNSCEAR, US-DOE, Environment Canada, Environment Agency) and European projects (ERICA and PROTECT). Derivation of environmental protection criteria under the EC-funded ERICA and PROTECT projects was based on laboratory studies considering (chronic) gamma radiation as the only stressor. Exposure to radiation or radionuclides under mixed contaminant conditions may trigger the proposed protection criteria.
The overarching aim of the proposed activities is to contribute to the prospective analysis of the likely implications of taking into account the multi-stressor context on (evolving) radioprotection regulation and standards.
The long-term objectives of this Task Group are to:
- Familiarize with approaches in other areas of environmental contamination and toxicology used for multiple stressor exposure, effect and risk assessment and identification of synergies;
- Understand the mechanisms and processes by which mixtures of contaminants interact to induce adverse effects on biota
- To develop a research framework and common research programme for the interpretation of multiple stressor exposure and effects
- Critical evaluation on how multiple stressor conditions may affect environmental radiation protection standards.
The short term objectives are
- To conduct a literature search and data collection on multiple stressor effects studies of which at least one of the stressors is exposure to radiation or radionuclides.
- Review of approaches in ecotoxicology for risk assessment in multiple stressor scenarios and evaluation of how these approaches can be applied in the context of environmental (radiation) protection
- Tailored to the needs multiple stressor experiments with interested researchers considering relevant mixtures and biota from different organisms groups following set guidelines.
IUR-REPORT 4 To help establish above long-term objectives, a questionnaire was set up to collate information (1) on knowledge gaps and to prioritise research requirements to address them and (2) on research groups working on the issue of multipollution, their interest in this study and/or capacity to conduct multipollutant studies. The results of the questionnaire were reported (IUR Report 4, 2006, cover page, annexes) and following priority areas for future R&D multipollution programmes were highlighted: (1) a better understanding how the multipollution context affects the behaviour of a single pollutant; (2) the study of additive and synergistic effects; (3) response of biota to multiple stressors; (4) optimised remediation strategies for multipollution scenarios based on improved knowledge on effect of environmental parameters on pollutants; (5) better understanding of uncertainties in a multipollution context.
Multiple stressor database containing in a structured way the results from a literature review on stressors studies, treatments, effects endpoints considered, observed effects.
Journal paper summarizing the state of the art of multiple stressor research on non-human biota with radiation as one of the stressors
Guidance document on approaches to study/assess multiple stressor effects
Mixture toxicity workshop organised by SCK•CEN from 22-24 September 2010. For registration see: www.sckcen.be/nl/evenementen/MIXTOX
Provisional TG membership
Nick BERESFORD (Centre for Ecology and Hydrology, UK)
Clare BRADSHAW (Stockholm University, Sweden)
Simon CARROLL (Centre of Biological Diversity, Sweden)
David COPPLESTONE (Environment Agency, UK)
Shoichi FUMA (National Institute of Radiological Sciences, Japan)
Rodolphe GILBIN (IRSN, France)
José Marcus GODOY (PUC, Brasil)
Tom HINTON (IRSN, France)
Nele HOREMANS (SCK•CEN, Belgium)
Carmel MOTHERSILL (McMAster University, Canada)
Deborah OUGHTON (University of Life Sciences, Norway)
Almudena REAL (CIEMAT, Spain)
Claude ROULEAU (Fisheries and Oceans, CANADA)
Lindis SKIPPERUD (University of Life Sciences, Norway)
Karolina STARK (Stockholm University, Sweden)
Synnove SUNDELL-BERGMAN (Vattenfall, Sweden)
Hildegarde VANDENHOVE (SCK•CEN, Belgium)
Nathalie VANHOUDT (SCK•CEN, Belgium)
Christine WILLRODT (Bundesambt für Strahlenshutz, Germany)
Satoshi YOSHIDA (National Institute of Radiological Sciences, Japan)
Tamara YANKOVICH (AREVA, Canada)
 Persons interested can contact the TG leader Hildegarde Vandenhove, firstname.lastname@example.org