SETAC Globe - Environmental Quality Through Science
 
  17 February 2011
Volume 12 Issue 2
 

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Ecological Risk Assessment highlights from SETAC-NA

Berit Berquist, Windward Environmental, and Katherine von Stackelberg, E Risk Sciences

Ecological risk assessment (ERA) topics were well represented at this year’s SNA Annual Meeting in Portland. Over 100 platform presentations and almost 150 posters were presented during the four-day meeting. Topics were wide-ranging, covering issues related to assessing risks associated with genetically-modified crops, use and interpretation of tissue residues, incorporating the Endangered Species Act (ESA) requirements in pesticide registration procedures, the role of computational toxicology in risk assessment, status and use of risk assessment guidance, modeling approaches to address population-level effects, evaluating unique compounds used in military applications, assessing and managing risks associated with human and animal pharmaceuticals, ecosystem diagnostics at varying scales, salinization of freshwater, harmonization of human health and ecological risk assessment methods and concepts, and use and applications of databases.

Transgenic Crops: Despite being widely-adopted in the USA, the global acceptance of genetically-modified crops remains highly contested. This is the first time there has been a session on ERA of transgenic crops at a SETAC conference. In addition to highlighting ERA refinements unique to plant-incorporated insecticidal technology, this well-attended session was organized to demonstrate applications of traditional ERA principles to evaluating risk of genetically-modified crop proteins on non-target organisms. Authors from academia, industry, and government presented current research, discussed challenges of analytical methodologies, made recommendations for the design of early tiered tests, and stressed the importance of thorough problem formulation for the risk assessment of current and future traits. All of the presentations were relevant to the current and future evaluation of biotech traits by registrants and agencies around the world.

Tissue Residue Toxicity: Estimates of toxicity based on tissue residue data are in principle superior to external dose-based estimates in that they represent the internal (absorbed) dose of contaminant to the organism. Comparison of a predicted tissue concentration to a tissue residue-based toxicity value might reduce the uncertainty introduced in backing out from a tissue residue to a dose. This set of talks focused on the latest data and results for tissue residue studies, largely from the field. For aquatic organisms, predicting tissue residues is fairly straightforward (e.g., equilibrium partitioning, bioaccumulation models). For terrestrial organisms, particularly at higher trophic level, this becomes more challenging due to greater environmental heterogeneity. Six of the eight talks in this session were based on research that will be presented in an updated and expanded edition of the popular text “Environmental Contaminants in Wildlife: Interpreting Tissue Concentrations” scheduled for release in February 2011. The session was co-chaired by the editors, Nelson Beyer and James Meador. A summary of this session appeared in the January 20 Globe. Presentations were focused on data compilations used to derive threshold tissue residue concentrations. Tissue thresholds were presented for selenium and DDE in bird eggs, total PCBs and toxicity equivalents in piscivorous mammals, and tributyltin and triphenyltin in whole-body fish and aquatic invertebrates. For these and other chemicals, it was concluded that the relationship between tissue residue concentrations and associated effects is becoming better understood and more refined. On the other hand, the knowledge about active pharmaceutical ingredients in tissue and related effects is rudimentary, but growing. The usefulness of insecticide tissue residue data in evaluating toxicity to aquatic organisms was questioned because of multiple analytical challenges.

Assessing Ecological Risk of Pesticides to Endangered/Threatened Species: The U.S. Environmental Protection Agency (USEPA) has a huge task ahead as part of the current pesticide registration review process, during which it must meet the requirements of the Endangered Species Act (ESA) to protect over a 1,000 federally-listed species. These requirements present a number of challenges including determining the overlap of species ranges and critical habitat with pesticide use sites on a national scale, considering future uses of pesticides and how that might change spatially, understanding and accounting for the life-history of each listed species, accounting for indirect effects, estimating off-site exposures, addressing the potential toxicity of mixtures, and relating potential sublethal effects to survival, growth and reproduction. This set of talks approached each of those issues, first by describing an effort to map habitat use on a national scale and what data sources are required for that, followed by a specific case study of a tiered approach to evaluating exposures and risks to glufosinate. Several talks in this session focused on aspects of estimating risk to Pacific Northwest salmon from exposure to acetylcholinesterase-inhibiting pesticides, concluding that direct effects on growth and survival of salmonids in Washington State are unlikely, and that probable exposure is far less than for hypothetical conditions assumed in ESA consultations. Other talks included approaches for developing a comprehensive national geodatabase for land cover and species habitats; a four-tiered approach for assessing indirect effects; the quantification of major pesticide source areas in California; and a refined evaluation of the effects of dimethoate on the California red-legged frog.

Computational Toxicology: Mathematical or computational modeling is not a new endeavor in biology or toxicology, but is a growing research area in toxicology. Many “omics” technologies (i.e., genomics, transcriptomics, proteomics, and metabolomics) are now being applied to study toxicological effects of contaminants, and researchers are finding themselves overwhelmed by the volume of data these technologies produce. This session provided a forum to discuss the roles that computational toxicology plays in environmental risk assessment, particularly in the mathematical, computational and statistical analysis and modeling of high dimensional omics datasets. It was convincingly demonstrated that computational toxicology has an important role to play in the predictive aspect of risk assessment, with many more challenges and new questions emerging. Some of these important new challenges include linking molecular effects to population effects; separating confounding environmental effects in the field to those observed in laboratory studies, predicting effects of mixtures based on data of single compound exposure, and improving extrapolation power across species. In the words of session co-chair Ping Gong, “It is widely accepted that math will rock the world. We believe computational toxicology will rock environmental risk assessment. We can foresee expanded computational toxicology sessions at future SETAC meetings.”

Ecological Risk and Related Ecological Assessments at EPA: Twelve Years after the Guidelines. This day-long session focused on ecological risk assessment guidelines, how they are being used, what is missing, and what might be coming next. The first set of talks focused on how existing guidance is being used, including the experience of one company in applying guidance over the years. There were several talks that gave the perspective from the Science Advisory Board, including specific recommendations for improving the ecological risk assessment process that rose out of a 3-year review project. EPA has recently developed a (soon-to-be) web-accessible, linked table that categorizes 58 documents identified as containing “guidance” on conducting ecological risk assessments. Speakers generally concluded that there is a lot of guidance that is underutilized, and there is a need for better communication to users of guidance, particularly with respect to risk managers. There seems to be a perception that “routine” issues don’t require detailed guidance, and that existing guidance doesn’t adequately address “simple” problems. Despite that, EPA is currently evaluating the development of several additional guidance documents including weight-of-evidence, quality assurance, systems approaches, multiple stressors, specific receptors (e.g., reptiles, amphibians, marine mammals), adaptive management, uncertainty analysis, life cycle analysis, and large scale assessments. The session concluded with the idea that as an alternative to additional guidance, ERA might benefit more from structured communities of practice through which the state of the practice can be discussed, and more informal methods of communication such as success stories, white papers, and case studies.

Advancing Population-Level Ecological Risk Assessment: An International Perspective. This day-long special symposium featured a variety of case studies and a discussion of specific modeling approaches that ran the spectrum from generating data (e.g., scaling mesocosm results to the situation in the field) to regulatory applications based on site-specific field data. Several of the talks focused on extrapolation of organism-level results using Daphnia and other species for use in Leslie matrix and other population-level modeling approaches. These talks addressed the ways in which observations can be scaled for use in true population-level modeling. On the other end of the spectrum, a number of the talks focused on regulatory applications of population-level models, recognizing that the non-cancer human health hazard quotient paradigm was not suitable for most determinations of ecological risk (save, perhaps, for endangered species) given that protection of individual organisms is not necessarily the regulatory focus.

Ecotoxicity, Fate and Risk Assessment of “Materials of Importance to the Military,” and Innovative Methods to Carry Out Such Investigations. Compounds used primarily at military installations, including energetics, smokes, and obscurants , pose unique ERA challenges in that there are often few data available, both with respect to predicting exposure as well as toxicity. This set of talks focused on those unique military compounds and ran the gamut from risks associated with unexploded ordnance and how changes in vegetative cover might be used to determine the locations of such ordnance, to phytotoxicity, to screening level soil concentrations (Eco-SSLs) based on potential ecological risks. One talk presented the results of several SERDP-funded studies to determine the toxicities of major nitramine and nitroaromatic energetics to invertebrates and terrestrial plants utilizing soils that support high relative bioavailability, then integrate the effects of weathering and aging in soil on organism exposures and toxicity benchmarks, to ultimately develop Eco-SSL values for ecologically relevant soil receptors. Another mesocosm study looked at toxicity of different concentrations of energetics in soil to specific plant receptors and developed threshold levels and/or dose response relationships for those.

Advancements in Environmental Risk Assessment and Management of Pharmaceuticals in the Environment. This series of talks focused largely on regulatory requirements and constraints associated with assessing potential risks, both human health and ecological, of pharmaceuticals in the environment. The regulatory situations in Canada, the EU, and the US were discussed, followed by a series of talks focusing on specific data that exist as well as data gaps. Pharmaceuticals often contain, or are characterized by, nanoparticles, so in many ways there is an overlap with methods to evaluate nanotoxicity, and one of the talks focused on the lack of basic data for ecotoxicity of pharmaceutical-based nanoparticles. Because many human-related pharmaceuticals are hormonally-based, there are issues related to endocrine disruption, and one of the talks focused on methods for improving the removal of endocrine disrupting compounds in waste streams using static bed biofilters. A related session, Risk Assessment of Veterinary Pharmaceuticals in the Environment, focused specifically on veterinary pharmaceuticals, particularly antibiotics. The first talk in that session discussed the regulatory process for approving veterinary drugs and described a tiered approach starting with simple comparisons of predicted environmental concentrations to no observed effect concentrations (and if such data are lacking, they must be obtained). The next talk focused on the situation in Europe, specifically with respect to methods for evaluating constituents found in manure, which is a primary pathway for veterinary pharmaceuticals to enter the environment. In a related talk, solid extraction and clean-up methods for targeted veterinary antibiotics in complex solid matrices, including fresh and processed manure, was discussed. These authors found that ultrasonic-assisted extraction was significantly more efficient in extracting antibiotics than other methods. The remainder of the talks focused on specific risk assessment applications under EU and US regulatory frameworks.

Emerging Contaminants and Ecosystem Diagnostics at Varying Spatial Scales. This session focused on quantifying trace organics in waste streams (e.g., non-point discharges) entering aquatic environments. One talk focused on legislation enacted in 2007 by Oregon to identify pollutants found in municipal wastewater following treatment. That process identified 118 priority persistent pollutants, and a framework for establishing trigger levels at individual water treatment plants. Several of the talks discussed potential diagnostic tools, including US EPA’s CADDIS, which is a causal analysis framework for determining potential causes of observed impairment in receiving water bodies and application of these tools in specific areas, including Ohio and Ontario. This session is also summarized in the January 20 edition of the Globe.

Salinization of Fresh Water: Toxicity and Risks. This series of talks focused on site-specific analyses of salinity as a cause of impairment in water bodies from Appalachia to Australia, and sources ranging from road salt to mountaintop mining. Salinity was found to cause impairment of macroinvertebrate assemblages in the coal fields of Central Appalachia based on a systematic weight-of-evidence approach. In a separate talk, the authors were able to develop species sensitivity distributions (SSDs) based on site-specific field data and using extirpation concentrations rather than some other metric (e.g., LC50s or chronic values). The causal analysis complemented the derivation of benchmarks, since by using field data it is impossible to control exposures and therefore establish causal relationships as in a laboratory setting. Another talk described a combination of field and laboratory methods using toxicity tests with reconstituted site waters to determine if combinations of major cations or major anions in site waters contributed to the toxicity in the absence of other contaminants, thereby focusing on causal mechanisms. Another laboratory study explores sulfate toxicity and impacts in mayflies with the goal of identifying causal relationships between exposures and observed reduced macroinvertebrate assemblages with respect to mining-related impacts.

Transferring Concepts between ERA and HHRA. This session focused on ways in which the risk assessment process can be leveraged to address both human health and ecological risk assessment needs, particularly with respect to predicting exposures. Themes that emerged included greater communication and discussions as sampling plans and analyses are being developed (e.g., detection levels appropriate for both kinds of analyses, what measurements will be taken, such as whole fish versus edible fillets, etc.). Several talks focused on bioavailability and bioaccessibility in the environment and the extent to which these are applicable across human and ecological receptors. Finally, one talk focused on the view that there are inherent limitations to harmonizing human health and ecological risk assessment methods.

Use and Application of Databases in Environmental Toxicology. This series of talks focused on specific databases that are available for use in ecological risk assessments. These include the Chemical Aquatic Fate and Effects (CAFĂ©) Database from the National Oceanic and Atmospheric Administration's Emergency Response Division (ERD); Web-ICE, available from www.epa.gov/ceampubl/fchain/webice, an extensive acute toxicity database for aquatic species; a web-based user interactive toxicological database capable of calculating protective cleanup levels specific to Texas; and, the Toxic Release Inventory (TRI) database from US EPA. Several additional talks focused on specific applications, such as developing threshold criteria under REACH, and how uncertainty factors can be used to derive screening level criteria. This session is further discussed in the January 20 issue of the Globe.

Authors’ contact information: beritb@windwardenv.com, kvon@erisksciences.com

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