Citation:

LAZORCHAK, J. M. AND MARK E. SMITH. A SURROGATE SUBCHRONIC TOXICITY TEST METHOD FOR WATERS WITH HIGH TOTAL DISSOLVED SOLIDS. Presented at SETAC North America, Millwaukee, WI, November 11 - 15, 2007.

Impact/Purpose:

The indeterminate condition of exposure indicator research stands to change markedly with the ability to connect molecular biological technologies with cellular or tissue effects and outcomes. Three focal areas of ecological research aim to develop a sequence of approaches where "the earliest recognizable signatures of exposure" (i.e., unique patterns of up- and down-regulated genes and proteins) are identified for numerous stressors, demonstrable in case studies and incorporated into Agency, State and Regional studies supported by EMAP and other programs.

Area 1, Computational Toxicology Research: Exposure assessment has historically been based on use of chemical analysis data to generate exposure models. While biological activity of chemicals has been recognized to be important for exposure risk assessments, measurement of such activity has been limited to whole organism toxicity tests. Use of molecular approaches will:

improve extrapolation between components of source-to-outcome continuum (source , exposure , dose , effect , outcome)

Using a systems modeling approach, gene and protein expression data, in small fish models (fathead minnow and zebrafish), will be integrated with metabolomic and histopathological data. This will assist in prediction of environmental transformation and chemical effects based on structural characteristics, and enhance quantitative risk assessments, including areas of uncertainty such as a basis for extrapolation of effects of endocrine disrupting chemicals, interspecies extrapolation, complex chemical mixtures and dose-response assessment.

Area 2, Ecological Research-Environmental Diagnostics: Development of molecular diagnostic indicators contributes to several of the GPRA Diagnostic Research Goals. Methods will employ DNA microarray technology and expression proteomics, focusing on species of relevance to aquatic ecosystem risk assessment. Significantly, these diagnostic indicators will open the door to understanding subcellular interactions resulting from exposure to complex chemical mixtures.

define relationship between genetic disposition of populations and degree/specificity of stressor-specific gene transcriptional response in aquatic organisms (fish and invertebrates)

identify of chemical mixture induced transcriptional "patterns" using microarrays and hyperspectral scanning - via collaboration with DOE Sandia National Labs

apply molecular indicators to watershed level stressor study, including pilot studies with targeted pesticides and toxins indicators

develop molecular indicators of exposure for invertebrates (Daphnia, Lumbriculus, Chironomus)

Area 3, Exposure Research in Endocrine Disruptors:

Subobjective 1: Develop exposure methods, measurement protocols, and models for assessment of risk management practices of endocrine disrupting compounds. As risk management approaches are identified and developed, there will be a need to identify, adapt and develop bioassay screening tools and other analytical methods to assess their efficacy. Measurements research will be performed to define management needs. This effort will entail cross-lab participation from NRMRL, NERL and NHEERL.

Subobjective 2: Determine extent of environmental and human exposures to EDCs, characterize sources and factors influencing these exposures, develop and evaluate risk management strategies to reduce exposures. In order to develop effective risk management strategies, it is important to understand the extent of exposures to endocrine disrupting compounds and factors influencing source-to-exposure-to-dose relationships.

apply molecular indicators of exposure to estrogenic compounds in selected wastewater treatment plants located in ten USEPA Regions

identify differential gene expression following exposure of fathead minnows to environmental androgens and androgen-like compounds

apply molecular indicators of exposu

Description:

Total dissolved solids (TDS) are often identified as a toxicant in whole-effluent toxicity (WET) testing. The primary test organism used in WET testing, Ceriodaphnia dubia, is very sensitive to TDS ions, which can be problematic when differentiating the toxicity of TDS from those of other contaminants. Daphnia magna is not as sensitive to common ion toxicity as C. dubia, but is still relatively sensitive to other contaminants. We used a 4-d static-renewal survival and growth method using D. magna to help identify the toxicant in an effluent from a discharger with elevated TDS. Because of the high TDS, we needed a test organism that was sensitive to most contaminants but less so to TDS ions. We compared the sensitivity of the 4-d D. magna method to the standard, short-term chronic 3-brood C. dubia method and to the 21-d D. magna chronic study to determine its applicability in WET testing, toxicity identification evaluations (TIEs), and other toxicity testing scenarios. The statistical endpoints calculated for the 4-d D. magna study were similar to the 21-d D. magna study but were substantially higher than for the 3-brood C. dubia study. For example, the IC25s for the 4-d D. magna study, the 3-brood C. dubia study and the 21-d D. magna study were (based on chloride): 1,449 mg/L, 377 mg/L, and 2,108 mg/L, respectively. Results indicate that this test would be useful for differentiating TDS toxicity from other contaminants in TIEs and as a compliance study method for dischargers where the presence of TDS ions is an ongoing issue.

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