Grantee Research Project Results
2016 Progress Report: Integrated Modeling Approaches to Support Systems-Based Ecological Risk Assessment
EPA Grant Number: R835795Title: Integrated Modeling Approaches to Support Systems-Based Ecological Risk Assessment
Investigators: von Stackelberg, Katherine Ellen , Stark, John D , Landis, Wayne G.
Current Investigators: von Stackelberg, Katherine Ellen , Stark, John D , Landis, Wayne G. , Sunderland, Elsie M.
Institution: Washington State University , Western Washington University , Harvard University
Current Institution: President and Fellow of Harvard College , Washington State University , Western Washington University
EPA Project Officer: Aja, Hayley
Project Period: June 1, 2015 through May 31, 2017 (Extended to December 31, 2018)
Project Period Covered by this Report: June 1, 2016 through May 31,2017
Project Amount: $651,708
RFA: Systems-Based Research for Evaluating Ecological Impacts of Manufactured Chemicals (2014) RFA Text | Recipients Lists
Research Category: Chemical Safety for Sustainability
Objective:
- Develop quantitative adverse outcome pathways (AOPs) for at least one legacy contaminant (e.g., mercury, PCBs) and one emerging contaminant (e.g., PFCs) to develop exposure-response profiles for use in a larger Bayesian Network-Relative Risk Model (BN-RRM).
- Develop several ecological risk case studies demonstrating the integration and application of one or more underlying process models to synthesize and integrate available data across levels of biological organization, including exposure estimates, quantitative AOPs, non-chemical stressors, and population models.
- Apply the BN-RRM framework to demonstrate how the approach generates quantitative predictions of potential ecological risk impacts at scales relevant to policy development and regulatory decision making.
Progress Summary:
We present a general approach for the integration of AOPs into a risk based analysis that puts the molecular biology into an ecological context with the endpoint being a population—an ecosystem service. We find there is no general framework for what is necessary to estimate risk and that there are many data gaps. These data gaps exist because of the lack of a suitable framework for setting research priorities and ensuring that a the cause-effect pathway is strongly documented. The classic FIFRA or TSCA tiered system of testing do not establish causality in such a manner.
Efforts during the past year have focused on continued development of two case studies. The first is site-specific, focusing on organophosphate exposures to salmon populations in the Pacific Northwest, a data-rich context based on a vetted AOP from the literature. The second is more general, focused on perfluorinated compound exposures to fish and birds using a “what-if” framework to back-calculate allowable exposures given target population declines.
Organophosphate Exposures and Salmon in the Pacific Northwest
Relying on a published (but largely unquantified) adverse outcome pathway analysis for acetylcholinesterase inhibition leading to acute mortality, we have developed a relative risk network model focusing on organophosphate pesticide (OP) exposure to Pacific salmon in four rivers in the Pacific Northwest. The model is currently parameterized for exposure to a single OP (chlorpyrifos) and incorporates habitat attributes (dissolved oxygen and water temperature) that independently contribute to population viability. Results suggest that OP exposures, dissolved oxygen, and temperature contribute similarly in each of the systems. At measured concentrations in Puget Sound, the OPs do have an effect but that effect does not overwhelm the environmental pathways. The effect is greater with all three OPs rather than just chlorpyrifos and with malathion at a higher concentration because it is the synergist.
The figure below presents some results. Panel A compares the distribution of population size after 20 years under current conditions for each of the four rivers. The y-axis shows the probabilities of increasing population size bins along the x-axis. Population distributions for the four rivers appear very similar, but there are differences and these are highlighted in Panel B. First, results for the Skagit River under current conditions are plotted across the population size bins (orange bars). The blue bars represent a simulation with no reduction in survivorship for either juveniles or adults. The final simulation (gray bars) sets both adult and juvenile fish population reductions at 20 percent. The output distribution (gray bars) is now in the range of the typical Skagit probabilities but without the longer tail, that is, the population size distribution shifts to the lower end of the distribution as compared to the blue bars, which shows a shift to a larger population size in the absence of chemical exposures.
This leads to potentially significant policy implications. Ecological risk assessment or ecotoxicology often use an EC20 (effect level at which 20 percent of the population responds) as a threshold level. These results suggest that toxicity to one contaminant, in the context of other stressors such as dissolved oxygen and temperature with similar outcomes, result in predictions of significant population declines, and that these individual threshold levels may not be sufficiently protective.
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The context for this case study is well-summarized by a recently published chapter (Lackey RT. 2017. Science and salmon recovery. pp. 69-94. In: New Strategies for Wicked Problems: Science and Solutions in the 21st Century, Weber EP, Lack DH and Steel BS, Eds. Oregon State University Press, Corvallis, OR, 223 pp.), which describes the challenges facing salmon recovery efforts.
Perfluorinated Compounds
Building on our literature review of ecological effects of perfluorinated compounds, focusing on immunotoxicity as shown in the table below as the basis for an AOP that ultimately leads to reduced fitness and sustainability of the population. A key field study in tree swallows (Custer CM, Custer TW, Dummer PM, Etterson A, Thogmartin WE, Wu Q, Kannan K, Trowbridge A and McKann PC. 2014. Exposure and Effects of Perfluoroalkyl Substances in Tree Swallows Nesting in Minnesota and Wisconsin, USA. Arch Environ Contam Toxicol, 66:120–138, DOI 10.1007/s00244-013-9934-0) demonstrates a clear concentration-response relationship between concentrations of PFOA in eggs/plasma and hatching success, the outcome of interest. We are in the process of developing conditional probability tables (CPTs) for the model. This involves detailed descriptions of how we derive each node based on four methods of deriving CPTs. To the extent possible, most of the model is built on measured values from the environment, exposure-response models based on data, and case learning.
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Future Activities:
In our final year, we will be preparing manuscripts for publication. We will also be presenting progress thus far at SETAC, Society for Risk Analysis, and selected regional meetings and conferences.
References:
Lackey RT. 2017. Science and salmon recovery. In: New Strategies for Wicked Problems: Science and Solutions in the 21st Century, Weber EP, Lack DH and Steel BS, eds. Oregon State University Press, Corvallis, OR, pp. 69-94.
Custer CM, Custer TW, Dummer PM, Etterson A, Thogmartin WE, Wu Q, Kannan K, Trowbridge A and McKann PC. 2014. Exposure and effects of perfluoroalkyl substances in tree swallows nesting in Minnesota and Wisconsin, USA. Arch Environ Contam Toxicol, 66:120-138, DOI 10.1007/s00244-013-9934-0.
Journal Articles:
No journal articles submitted with this report: View all 13 publications for this projectSupplemental Keywords:
uncertainty, systematic review, influence diagrams, Bayes network model, probabilistic, decision analysis, integrated assessment modelsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.