Adapting EDC Bioassays to Monitor Performance of Risk Management Processes

Impact Statement : Often, the performance of risk management techniques is evaluated by measuring the concentrations of the chemicals of concern before and after risk management efforts. However, using bioassays and chemical data provides a more robust understanding of the effectiveness of risk management strategies. For example, bioassay testing evaluates the aggregate effect of the environmental sample on the reporting organisms, and thus includes aspects such as environmental matrix effects, sorption/desorption behavior, bioavailability, and chemical mixture interactions. As a result, bioassay testing can demonstrate changes in toxicity rather than merely inferring risk reduction from chemical concentrations. Also, when bioassays are used to evaluate samples following risk management techniques, increased responses are observed in some cases. Whether these increased responses are due to incomplete treatment or toxicity introduced through process amendments, these responses can be identified through bioassay testing and risk management techniques can be altered to correct the problem. The combination of chemical and bioassay data has been helpful in evaluating risk reduction technologies treating soils contaminated with hazardous wastes. Due to the limited knowledge about the endocrine activity of various chemicals and their degradation products, bioassays are very important in evaluating the performance of EDC risk management treatments.

"Red" Fathead minnow photo by Konrad Schmidt

Project Description/Current Status: Overtime, several EDC bioassays have been developed. However, these bioassays are developed to meet the needs of the exposure and effects research, and not necessarily the needs of risk management projects. As a result, assays may need to be adapted to suit risk management purposes. This project started by canvassing the peer reviewed literature Assays were evaluated based on: reported sensitivity, range of applications and chemicals studied, acceptance in the academic community, the details of the assay protocol, and the EDSTAC Tier I Screening Battery recommendations. Practical concerns such as cost, time, equipment and space needs, and personnel skills were also included in the evaluation process. Since most current risk management projects are concerned with estrogenic compounds, androgenic and thyroid assays were not considered at this time. Bioassays which seemed to be most promising for use in the risk management context and for EPA’s National Risk Management Research Laboratory’s (NRMRL’s) EDC projects were evaluated further.

The process of adapting the assay for risk management use involves several aspects such as: establishing a quality assurance and quality control framework for conducting these assays and developing sampling techniques for various environmental media and different concentration ranges. Many EDC bioassays have been developed to assess endocrine disruption by pure compounds. Since risk management EDC projects involve EDCs in environmental matrices such as groundwater, surface waters, sediments, or soils, assays and sampling procedures will need to be developed to cope with these different matrices. Additional controls may be needed to understand assay results in the context of environmental samples.

Results: The bioassay project is working with colleagues in the Molecular Ecology Research Branch of EPA’s National Exposure Research Laboratory (NERL) to adapt an assay for risk management projects. David Lattier, Jim Lazorchak, and Greg Toth have developed an assay which detects transcription of the vitellogenin gene in several fish species. Vitellogenin (Vg) is an egg yolk protein typically produced by female fish during spawning season. However, vitellogenin transcription has been observed in male fish exposed to estrogenic compounds. The MERB Vg mRNA assay involves exposing naive male fish to environmental samples, and measuring Vg mRNA production. The Vg mRNA assay was selected for several reasons. First, the assay measures the response in fish, an ecologically relevant organism. Second, as a whole organism assay, metabolic activation and other reactions will be included in the Vg mRNA assay. Third, the Vg mRNA assay has demonstrated effects to 17 ß-estradiol in the ng/L range and has been used in risk management EDC projects. Lastly, the Vg mRNA assay is logistically practical, and the MERB staff have been helpful in the assay selection process.

Contact Information: For more information concerning Adapting EDC Bioassays to Monitor Performance of Risk Management Processes, please contact Carolyn Acheson, Ph.D. at phone (513) 569-7194 or fax (513) 569-7105.

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Adapting EDC Bioassays to Monitor Performance of Risk Management Processes

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