Biomonitoring of Environmental Status and Trends (BEST)
Synthesis Projects and Activities (Comprehensive Biomarker Reviews)

This web page provides information on each of the biomarkers reviewed for use in the BEST program.

To monitor the exposure of organisms to xenobiotic chemicals and the effects of such exposure, the BEST program (Biomonitoring of Environmental Status and Trends) incorporates biological indicators or biomarkers spanning all levels of biological organization, from the biochemical to the population and community levels.

Through a series of workshops and meetings from which the list of candidate methods for the BEST program was derived (BEST 1996), it became evident that the information base upon which to judge the validity of biomarkers varied widely. Some biomarkers are widely used and accepted in the field of environmental toxicology, but their use in monitoring has not been tested nor has their voluminous literature been tabulated, summarized, and thoroughly evaluated with respect to the above criteria.

For other biomarkers proposed for use in the BEST program, comparatively little is known about the extent to which contaminants influence their outcomes. Therefore a series of synthesis activities was undertaken to summarize and assess the extant literature and data available for the biomarkers recommended for use in the BEST program, beginning with those methods being tested in pilot studies.

Schmitt, C.J., T.M. Bartish, V.S. Blazer, T.S. Gross, D.E. Tillitt, W.L. Bryant, and L.R. DeWeese. 1999. Biomonitoring of Environmental Status and Trends (BEST) Program: Contaminants and their effects in fish from the Mississippi, Columbia, and Rio Grande basins. Pp. 437-446 in Morganwalp, D.W. and H.T. Buxton, eds. U.S. Geological Survey Toxic Substances Hydrology Program—Proceedings of the technical meeting. Charleston, S.C., March 8-12, 1999. Volume 2 of 3—Contamination of hydrologic systems and related ecosystems. U.S. Geological Survey-Water Resources Investigations Report 99-4018B. W. Trenton, NJ. http://toxics.usgs.gov/pubs/wri99-4018/Volume2/sectionD/2507_Schmitt/index.html

Search BEST Bibliography     SEARCH Bibliography from BEST Synthesis Documents

Measurement of ethoxyresorufin-O-deethlyase (EROD) activity in fish is a well-established in vivo biomarker of exposure to particular planar halogenated/polycyclic aromatic hydrocarbons (PHH/PAH) and structurally related compounds. Providing evidence of receptor-mediated induction of cytochrome P450-dependant monooxygenases (the CYP1A subfamily specifically) by xenobiotic chemicals, EROD is a highly sensitive indicator of contaminant uptake in fish.

           Searchable tabulated data from published articles where EROD is used as a biomarker in fish:

  1.   Chemical inducers of hepatic EROD activity in fish
  2. Chemical inhibitors of hepatic EROD activity in fish
  3. Laboratory investigations of hepatic EROD activity in fish
  4. Estimated basal level of EROD activity in fish species
  5. Field studies of fish EROD induction in response to contaminant exposure
  6. Caging studies of fish EROD induction in response to contaminant exposure

The H4IIE rat hepatoma cell line bioassay (H4IIE cell bioassay) is an in vitro test used to detect and semi-quantify specific contaminants and classes of contaminants chemically extracted from environmental matrices such as sediment, water, and organisms (whole or specific tissues).

The H4IIE cell bioassay measures the catalytic activity of cytochrome P4501A1 (CYP1A1), a mixed-function oxidase (MFO) enzyme, as 7-ethoxyresorufin-O-deethylase (EROD) activity or aryl hydrocarbon hydroxylase (AHH) activity in cultured rat liver cells exposed to environmental extracts.

The H4IIE cell bioassay is consequently useful for characterizing, the presence of CYP1A1-inducing compounds including certain polycyclic aromatic hydrocarbons (PAH) and related compounds (e.g., nitrogen heterocyclics and sulfur-, oxygen-, nitro-, amino,- and alkyl-substituted PAH) and polyhalogenated hydrocarbons (PHH) in environmental samples.

Tabulated data from published articles where H4IIE cell bioassay is used as a biomarker. (coming soon)

Two types of assessments have been directed toward whole fish or gross (visible to the naked eye) observations: the incidence of gross external pathological disorders and a more comprehensive necropsy-based fish health assessment internal and external).

Changes at this level represent an advanced stage, i.e., when a high incidence of skin abnormalities or hepatic tumors are found there may already have been a significant impact on the population. Lesions observed at this level also suggest that adaptive mechanisms – immunological, physiological, biochemical – are overwhelmed. However, it must be recognized that even lesions at this level can heal or be resolved and are not necessarily life-threatening.

Reproductive success can be a reliable indicator of a population’s reproductive health and potential, but it is often difficult to evaluate, especially in aquatic environments where fish and other wildlife are not easily contained or convenient monitoring. Consequently, the development of techniques for measuring other reproductive indicators (e.g., sex steroid hormones, vitellogenin, gonadosomatic indices, and gonadal histopathology) has aided researchers in assessing the reproductive health of many fish species. These reproductive biomarkers provide quantifiable measures of biochemical, physiological, or histological changes that occur throughout the reproductive cycle.

Reproductive biomarkers are useful for (1) examining the effects of environmental stressors, such as chemical contaminants, eutrophication, and temperature fluctuations, on an individual or population, (2) predicting future reproductive trends and population abundance by serving as early indicators of sublethal effects of environmental stressors, and (3) providing insight into the causal relationships between reproductive failure and environmental stressors.

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