||17 January 2013
Volume 14 Issue 1
Reports from the Berlin World Congress Sessions
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- Ecotoxicity, Fate and Risk Assessment of Materials of Importance to the Military
Jennifer Trowell, Azimuth Group
Unsurprisingly, much of what plagues the risk assessment of, and fuels research into, materials of importance to the military is uncertain and unknown. These same unknowns and uncertainties form the issues common in many risk assessments. Hence, the findings and themes presented in this session held during the SETAC North America annual meeting in Long Beach, are applicable to all “materials,” not just those of importance to the military.
The first two talks, which were presented by James Phibbs (AECOM), focused on an ecological and human health risk assessment of a hypothetical rare earth element mine site. Rare earth metals are used in a variety of technologies, including green technology and technology of interest to the military. Rare earth metals typically co-occur in mixtures and in association with radioactive elements, so understanding mixture toxicity and radioactive exposure is key. Furthermore, rare earth metals are rarely studied, so there are no guidelines in place for soil or water concentrations, and toxicity reference values (TRVs) and reference doses are hard to come by. However, a key theme of both talks was that a lack of guidelines or standards doesn’t mean there are no risks; rather, due diligence should incentivize investigation into the primary literature to probe the potential for harm and possibly risk.
The second two talks presented the work of Hebert Allen and Dominic Di Toro (University of Delaware) who investigated and modelled the sorption and desorption of organic munitions constituents to soil. The first talk presented the laboratory work that formed the basis of the data set for the modelling work presented second. It was uncertain which played a greater role in sorption, organic carbon or clay, but the results showed a multi-linear model that incorporates the partition coefficients of the organic compound with both organic carbon and clay best describes the results of the laboratory work. The results of these works would be applicable for modelling sorption and desorption of many organic contaminants, filling in the gaps in understanding of bioavailability of organic contaminants in the soil.
Three talks in this session were cancelled due to travel funding restrictions. The final talk of this session, presented by Eun Hea Jho (Seoul National University), presented the use of hydrogen peroxide to break down 2,4-dinitrotoluene (2,4-DNT, a breakdown product of TNT) in soil co-contaminated with lead and copper. Remediation of soils contaminated with 2,4-DNT with hydrogen peroxide was shown to be highly effective, but prior removal of the heavy metals was suggested to improve efficacy. However, applicability of this technology for remediation on a large scale was not presented, so its usefulness is uncertain.
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- Sediment to Tissue and Tissue to Sediment—Bioaccumulation Measurements, Modeling and Remedial Decision Making
Nancy Judd, Windward Environmental and Henriette Selck, Roskilde University
The uptake of chemicals by organisms from the abiotic compartment, and transfer within the food web affects organisms all the way up the food chain. There are a variety of approaches to quantify the relationship between sediment and tissue chemical concentrations, including laboratory- and field-based measurements. There are also a number of modeling approaches for describing sediment- tissue relationships ranging from biota-sediment relationships, to pharmocokinetic/pharmacodynamic modeling and food web modeling.
Bioaccumulation measurements and modeling tools are routinely used in risk assessments. Bioaccumulation models can also be used in remedial decision-making to estimate acceptable sediment concentrations from risk-based tissue concentrations and to evaluate how effective different remedial alternatives will be. The "Sediment to Tissue and Tissue to Sediment—Bioaccumulation Measurements, Modeling and Remedial Decision Making" session at the SETAC North America meeting in Long Beach explored innovations in bioaccumulation evaluation and modeling from experimental (i.e., laboratory and field-based efforts) to applied approaches.
The session began with three presentations on metals. One focused on uranium availability (this seems to be affected by many of the Biotic Ligand Model parameters). The second provided a novel sediment triad approach including factors potentially helpful in predicting metal accumulation (such as organic carbon content of the sediment). The third combined field and lab work to predict tissue concentrations, determine tissue residence time and understand exposure history. The fourth talk considered the relationship strength, significance and uncertainty for tissue sediment statistical models of organic chemicals used for risk assessments and remedial decision-making. This was followed by two talks on biodynamic modeling. The first presented a site-specific application of the selenium biodynamic model (site-specific values canceled out in the model leaving the biota accumulation factor equation). The second envisioned the potential of the biodynamic model as a regulatory tool. The final two presentations focused on mechanistic modeling. One estimated the relative contribution of sediment versus water to tissue burden (20-40% of the body burden in Dungeness crab in Victoria, BC were thought to be associated with water exposure). The final talk promoted the use of mechanistic modeling for higher trophic level species, such as orcas, in order to look beyond endpoints for benthos when setting sediment quality guidelines. Overall these presentations provided several novel approaches, from laboratory to field, for understanding and application of biota-sediment relationships.
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- Advances in Assessing the Bioaccumulation and Bioconcentration of Ionizable Organics
Mark Bonnell, Environment Canada, Bryan Brooks Baylor University and Todd Gouin, Unilever U.K.
The session "Advances in Assessing the Bioaccumulation and Bioconcentration of Ionizable Organic" was organized jointly between the SETAC Bioaccumulation and Pharmaceutical Global Advisory Groups. The objective of this session was to explore the advances in assessing the bioaccumulation and bioconcentration of ionizing and permanently charged organic substances, such as those used in pharmaceutical applications. Presentations included advances in the mechanistic understanding of chemical permeation and distribution using in vitro and in vivo methods as well as modeling of bioaccumulation and bioconcentration of ionizing and permanently charged chemicals. Presentations also included regulatory drivers for the assessment of ionizing substances and techniques that can be used to profile chemicals that do not fit the baseline of neutral narcotic chemicals.
Chemical management programs strive to protect human health and the environment by accurately identifying persistent, bioaccumulative and toxic (PBT) substances or those substances that may cause adverse effects from exposure by restricting their release to the environment. It is notable that the fundamental principles underlying the hazard assessment of PBT substances have primarily been developed on the basis of our understanding of the environmental fate and behaviour of neutral non-polar organic chemicals, assuming generic exposure pathways and generic toxicological modes of action. This baseline may not fit for ionizing substances because often ionized chemicals are more bioavailable (e.g., from acid groups) in the environment and if they contain substituents (functional groups) that are “reactive” (e.g., carbonyl or epoxide groups), the combination of the two can lead to adverse effects at far lower concentrations in water than neutral organic chemicals. Chemicals such as pharmaceuticals fit this alternate paradigm and are often designed to permeate tissues to produce a biological interaction (e.g., receptor-mediated interactions). Consequently, care must be taken when current regulatory criteria and approaches designed based on legacy neutral narcotic chemicals are applied to reactive highly ionized compounds.
In this session presenters offered in silico, in vitro and in vivo methods to help us understand chemical uptake and distribution in aquatic organisms and importantly pointed out that some ionizing chemicals appear to biomagnify in air-breathing organisms, but may not exceed bioaccumulation criteria established for aquatic organisms (i.e., potential false negatives). We learned that understanding the mechanisms of bioaccumulation as a function of absorption, distribution, metabolism and elimination (ADME) properties of substances is critical for understanding how ionizing chemicals get taken up and eliminated by biota. We saw that ADME properties and mechanistic bioaccumulation models tailored for ionizing substances can be used to profile chemicals alongside criteria for regulatory purposes and in particular for determining the potential for adverse effects of ionized “reactive” chemicals, such as those that undergo covalent interactions. It was pointed out that for polar and ionizable compounds, differential partitioning to different biological substrates, such as membranes, should be considered and can be modeled using mechanistic techniques. Laboratory techniques such as immobilized artificial membranes (IAM) were offered as one way to understand the effect of pH on membrane partitioning. We also learned that there are regulatory initiatives underway tailored specifically to examine the ecological impact of pharmaceuticals in the environment and that research from sessions such as this can help in regulation building.
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- Analysis, Fate and Disposition of New Poly- and Per-fluorinated Organics in the Environment
Jonathan Benskin, AXYS Analytical Services and Claudia Müller, Stanford University
In the past, research on perfluoroalkyl acids (PFAAs) has focused on perfluoroalkyl sulfonates, such as perfluorooctane sulfonate (PFOS) and perfluoroalkyl carboxylates (PFCAs), e.g. perfluorooctanoic acid (PFOA) but recently new classes of PFAAs and PFAA-precursors have emerged. In this session, an overall picture of current topics in the environmental chemistry of PFAAs and PFAA-precursors was covered, with a particular emphasis on emerging organofluorine substances.
Environmental contamination of PFAAs is a global issue. PFAAs have been measured throughout the environment, including humans and remote Arctic wildlife, precipitation, marine and freshwater bodies. Despite recent phase-out initiatives, including the nomination of perfluorooctane sulfonate (PFOS) to the United Nations Stockholm Convention, the manufacture and use of PFAAs continues today. Meanwhile PFOS concentrations continue to increase in humans and wildlife from some parts of the world. Furthermore, the environmental presence of organofluorine pollutants has expanded beyond PFOS and PFCAs. Several poly- and per-fluorinated substances are far less understood and include perfluorophosphonates, polyfluorinated phosphoric diesters, fluorotelomer acids, fluorotelomer alcohols, perfluoroalkylsulfonamides (PreFOS), cyclic perfluorinated acids, fluorinated siloxanes, polyfluorinated alkanes, fluorotelomer acrylates, hydrofluoroethers, fluorinated dioxins and fluorinated polymers. Few data are available on these ubiquitous emerging organofluorines and the extent to which they contribute the burden of PFAAs in the environment.
The session on per- and poly-fluoroalkyl substances (PFASs) at the SETAC North America Annual Meeting in Long Beach included presentations from industry, government and academia focusing specifically on the measurement, occurrence and behavior of emerging organofluorines. In the platform session, Mark Strynar (USEPA), Anne Myers (University of Toronto), Jenn Field (Oregon State University) and Sonia Dagnino (USEPA) presented a variety of high-resolution mass spectrometry-based techniques (including time-of-flight, fast atom bombardment and ion cyclotron resonance) to identify novel commercial organofluorines and/or their transformation products. Linda Lee (Purdue University) presented a comprehensive study on the biodegradation of polyfluoroalkyl monomers in soils while Ning Wang (DuPont) presented work on the remobilization and biodegradation of 5:3 polyfluorinated acid by earthworms. The session was completed with a new global PFAS emission inventory presented by Zhanyun Wang (ETH Zurich). Highlights of the poster session included a novel advanced oxidation process to quantify the total oxidizable PFAA-precursors in aqueous fire-fighting foam (AFFF)-contaminated groundwater (E. Houtz, UC Berkley), enantiomer-specific analysis of PFOS in Chinese and Swedish blood (Y. Liu, University of Alberta) and the identification of a new class of PFAS, the polyfluorinated amides, which could be a significant and previously unrecognized source of perfluoroalkyl carboxylates in the environment (D. Jackson, University of Toronto).
The take-home message from the session was that research on PFASs encompasses much more than simply PFOS and PFCAs and that considerable attention should be given to emerging PFASs.
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- Use of Management Practices to Control and Treat Agricultural and Urban Runoff
Bryn Phillips, University of California-Davis, Brian Anderson, University of California-Davis and Matt Moore, United States Department of Agriculture-Agricultural Research Service National Sedimentation Laboratory
Agriculture and urban development have long been considered top sources of impairment for water bodies throughout the United States and abroad. It is estimated that human activities have altered 77% of Earth's ice-free land, with about half of that land in direct use by humans for agriculture and urban development. The top three impairments of US water bodies are pathogens (15%), metals (non-mercury; 10%) and nutrients (10%). While metals are typically a result of urban runoff, pathogens and nutrients are common contaminants from both urban and agricultural runoff.
Storm water and irrigation runoff from urban and agricultural landscapes often contain contaminant mixtures which may impact aquatic receiving systems. These include current-use and legacy pesticides, hydrocarbons, metals, nutrients, pathogens and heavy particle loads leading to increased sedimentation. With increased regulation of urban and agriculture runoff, there is growing emphasis on implementing practices to reduce pollutant loading. These include, but are not limited to, on-farm techniques such as vegetated treatment systems, settling ponds and water and nutrient efficiency systems and low-impact development practices in urban settings.
The urban runoff highlights from the Long Beach session on use of management practices to control and treat runoff discussed the reality of not treating all urban runoff. Source control is the economically practical, efficient and beneficial alternative. A case study from San Mateo, California emphasized this point. Other urban runoff management studies were presented, included studies of the effectiveness of rain gardens and vegetative swales for parking lot treatment. A final urban runoff presentation focused on a protecting groundwater by using underground injection.
Intertwined with talks on urban management issues were several speakers who focused on management practices used to treat agricultural runoff. Highlights included a talk on sediment capping with phosphorus inactivation agents in a New Zealand lake that had been internally loaded with nutrients; successful use of an integrated vegetated treatment system (ditches) to reduce pyrethroid pesticides and an organophosphate-hydrolyzing enzyme; initial small-scale success of rice fields in reducing loads and concentrations of herbicides and insecticides in simulated agricultural runoff; and initial use and design of a novel microbial-based bioreactor to reduce nutrient runoff associated with ornamental plant nurseries. Rounding out the highlights of agricultural practices was the unique molecular efforts of inserting an anti-atrazine antibody fragment into Lemna minor, an aquatic plant commonly used in phytoremediation efforts.
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- Wildlife Ecotoxicology Supporting Management Decision Making
Katrina Leigh, Environ and Tim Bargar, US Geological Survey
The session " Wildlife Ecotoxicology Supporting Management Decision Making," held during the Long Beach meeting, covered a range of wildlife topics highlighting the many different kinds of information critical for effective management decision making. Running the gamut from lab-based studies to restoration of wildlife habitat, with each type of information providing a piece of the puzzle for effective wildlife management in the face of chemicals present in the environment.
Topics covered fell into four general categories:
- Lab-based studies documenting effects and mechanisms of actions of chemicals on specific species
- “On the ground” studies that make use of existing data or infrastructure to identify effects of chemicals to wildlife
- Modeling and predicting risks to wildlife from chemical use
- Stewardship of wildlife resources and restoration of habitats critical for wildlife
Lab-based presentations (Effects of Embryonic Exposure to PCBs on heart development in avian laboratory species, M. Ottinger) highlighted the need to understand the mechanism of action of chemicals to specific species, sensitive developmental stages and detrimental environmental concentrations. This type of information allows the manager to make critical decisions regarding the types of exposure and chemicals that need to be managed or remediated for the safety of wildlife populations.
Unique, “on the ground” studies (Post-registration wildlife incident monitoring schemes can be used to evaluate management decisions for pesticides, P. Berny and Homing pigeons as useful biomonitors for atmospheric environmental decisions, R. Halbrook) remind us that sometimes the most useful data for evaluating historic management decisions or making new ones are those that are already available; for example, using post-mortem necropsy data obtained from the SAGIR network in France to identify non-target poisoning by pesticides and linking these cases back to key historic management decisions for evaluation purposes. Perhaps the infrastructure for obtaining key data is already in place, as in the case of collaborating with homing pigeon enthusiasts around the world to monitor the effects of air pollution on wildlife (and humans) by using homing pigeons as a surrogate species.
Spatially explicit exposure models can help bridge the gap between toxicology and realistic exposures of chemicals to wildlife (Improving risk predictions through the integration of space and habitat suitability: an application of the spatially-explicit exposure model (SEEM), M. Johnson). This approach allows the manager to evaluate whether the predicted exposure to a chemical is harmful to wildlife and what, if any, management decisions need to be taken to ensure safety of local populations.
Finally, these data, from lab and field studies to exposure models, can help inform the responsible remediation of critical wildlife habitat, help restore populations of endangered wildlife and promote the concept of stewardship of wildlife resources. Responsible use of toxicological, environmental and modelled data can aid in plans for restoring at risk wildlife populations (Demystifying Toxic Reference Values for Bald Eagles in Assessment of Damages, W. Bowerman) and restore wildlife habitat back to original conditions (Science tailored to the Natural Resource Damage Assessment and Restoration Program, N. Beyer). Importantly, restoration work (Ecological Risk Assessment for Decision making in Restoration of the Bolsa Chica Lowlands, California, H. Ohlendorf) can not only restore original habitat, but also work to improving and providing habitat for at risk species.
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