Emerging Issue: Use of Biomarkers to Assess and Quantify Injury in Natural Resource Damage Assessments

Dr. Nicholas Gard and Ms. Linda Ziccardi

Feature

Natural resource damage assessments (NRDAs) focus extensively on methods to determine whether injuries (defined as measurable adverse changes in the quality or viability of natural resources resulting from exposure to oil or a hazardous substance) have occurred, and to quantify the service losses resulting from those injuries. A rapidly emerging trend is for trustees to rely on biomarker measurements in individual organisms as a short cut to determining population scale injuries/changes as an input to service reductions calculations. This trend adds convenience to the process, but at the same time it introduces significant uncertainties.

Under U.S. Department of the Interior (DOI) NRDA regulations, determination of injury to biological resources primarily relies on measurement of sub-organism or organism-level (i.e., individual-level) endpoints. For example, 43 CFR §11.62(f)(1)(i) defines injury as occurring if a biological resource or its offspring have “undergone at least one of the following adverse changes in viability: death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including malfunctions in reproduction), or physical deformations.” By contrast, for quantification of injury, the DOI regulations state, “the extent to which the injured biological resource differs from baseline should be determined by analysis of the population or the habitat or ecosystem levels” (43 CFR §11.71(l)(1)). Thus, there is an inherent mismatch between the level of biological organization at which injuries are defined and at which they are quantified. This mismatch creates problems in NRDA cases because of the difficulty in extrapolating data for injury identification (i.e., has injury occurred) to injury quantification (i.e., measuring the extent of the injury). This is important because injury quantification is the basic metric for determining the scope of liability (restoration or monetary compensation) in an NRDA claim.

As noted above, determination of injury to biological resources is often made on the basis of adverse effects to an organism. Typically, these types of effects might be a measure of some reduction in survival, growth, or fecundity. However, as defined by the DOI NRDA regulations, injury determination can also be made on the basis of adverse effects at the cellular or subcellular level (i.e., biomarkers). The NOAA (1996) guidance document for NRDA under the Oil Pollution Act of 1990 (OPA) defines a biomarker as: “a biochemical, physiological, or histological indicator of either exposure to, or effects of, xenobiotic contaminants such as oil at the suborganismal or organismal level.” The problem regarding data extrapolation as described earlier (extrapolating data for injury identification to injury quantification) tends to be more intractable for injury determinations that rely on biomarkers than those that rely on toxicity endpoints or other measures of organism-level effect. For example, injuries such as reduction in survival, growth, or fecundity can be extrapolated to vital rates of the population, such as abundance, productivity, or survivorship, using fairly well established ecological modeling methods. However, no such methods exist for reliably extrapolating physiological or metabolic effects to populationor ecosystem-level effects. In fact, the relevance of many biomarker endpoints to the growth, survival, or reproduction of an individual organism is unknown. Thus, extrapolation of these measurement endpoints to population-level endpoints introduces substantial additional uncertainty to injury quantification[1].

Despite these limitations, natural resource trustees have implemented injury assessment approaches using biomarkers to predict ecological service losses[2] in many NRD cases, including the assessments conducted for the Lower Fox River/Green Bay, and the Exxon Valdez reopener (described below). In past CERCLA cases and oil spills, trustees used data such as counts of killed fish and birds, toxicity studies, or decreases in population abundance or fecundity to quantify injury. Today it is becoming more commonplace for trustees to measure biomarker endpoints such as enzyme induction or inhibition, physiological responses, reductions in growth, immunosuppression, and histopathology to identify natural resource injuries, and then apply simplistic approaches to infer some level of service reduction in the injury quantification phase of an NRDA. These biomarker-based injurydetermination methods are gaining popularity among trustees because they are relatively easy to perform, inexpensive, provide rapid approaches to measure exposure, and are generally more sensitive to lower contaminant concentra-tions than endpoints such as growth, survival, or reproduction.

One prominent example of the application of biomarkers is in the Exxon Valdez NRDA, where recent “reopener” claims by the Trustees are based, in part, on data from molecular endpoints such as cytochrome P450 CYP1A[3] (liver enzyme) induction and other assay techniques. The trustees are attempting to use these noncontaminant- specific biomarkers to allege continuing exposure 16 years after the spill at a very small number of sites in a vast ecosystem, and to make the case for population-level impacts.

Measurements of effects or use of biomarkers at the cellular or subcellular levels are not recommended for injury quantification because of the high degree of uncertainty in translating such measurements into population-level effects. For these reasons, Exponent recommends developing technical strategies in support of NRD claim defense that focus on evaluating impacts at the organism, population, or com-munity levels to counter trustee injury claims based on biomarker studies.

Dr. Nicholas Gard is a Managing Scientist in Exponent’s EcoSciences practice. He specializes in ecological risk assessment and natural resource damage assessment, with an emphasis on the evaluation of effects of chemicals on terrestrial, wetland, and estuarine ecosystems. He has 19 years of experience in toxicology, ecology, and wildlife biology. Dr. Gard has conducted natural resource damage assessments to quantify injuries to fish, birds, and mammals from exposure to PCBs and mercury, and to analyze habitat restoration requirements needed to appropriately compensate for damages resulting from these injuries.

Ms. Linda Ziccardi is a Senior Ecologist in Exponent’s Eco- Sciences practice. She is an ecologist with 16 years of experience evaluating environmental impacts at industrial and development sites nationwide. Her particular expertise is conducting CERCLA ecological risk assessments and natural resource damage assessments for chemically impacted sites. Her projects have included fish, wildlife, and vegetation baseline assessments, bioaccumulation studies, and quantitative risk analyses.

References

Forbes, V.E., A. Palmqvist, and L. Bach. 2006. The use and misuse of biomarkers in ecotoxicology. Environ. Toxicol. Chem. 25:272–280.

NOAA. 1996. Preassessment phase. Guidance document for Natural Resource Damage Assessment under the Oil Pollution Act of 1990. Available online at http://www.darp.noaa.gov/ library/pdf/PDF-TP.PDF.

Footnotes

[1] The limitations in using bio-markers to assess chemical impacts on populations have been discussed extensively by others; see, for example, Forbes et al. (2006).

[2] In the quantification phase of a NRDA, an attempt is made “to establish the extent of the injury to the resource in terms of the loss of services that the injured resource would have provided had the discharge or release not occurred” (43 CFR §11.13(e)(2)(i)), where services are defined as “the physical and biological functions performed by the resource including the human uses of those functions” (43 CFR §11.14(nn)).

[3] As measured by ethoxyresorufin O-deethylase (EROD) activity assays, or gene mRNA expression.