ASSESSMENT OF METHODS FOR ESTIMATING ECOLOGICAL RISK IN THE TERRESTRIAL COMPONENT: A CASE STUDY AT THE BAIRD & McGUIRE SUPERFUND SITE IN HOLBROOK, MASSACHUSETTS

Abstract

Predictive, bioassay, and field methods were compared with regard to assessing conditions and risks to terrestrial biota at a Superfund site contaminated with pesticides. Research indicated that predictive methods could result in large uncertainties, especially when attempting to estimate food chain transfer from soil to higher trophic levels (birds and mammals). Of the examined predictive methods, the soil-to-earthworm model yielded results that agreed best with field observations and literature values. Laboratory and in-field bioassays on soils provided good information on the potential toxicity of soils and the potential for bioaccumulation. In-field bioassay tests with earthworms were useful for defining the spatial distribution of toxic soils at the site as well as for indicating potential bioaccumulation in invertebrates. An attractive feature of in-field bioassays is that samples do not have to be removed from the field and assessments can begin to be made in the field. The importance of performing reality checks by conducting field studies was clearly demonstrated in our study with regard to the soil invertebrate community as well as birds and mammals. The main advantage of the field studies is that they provide direct information on conditions and thus aid in the interpretation or application of laboratory data. Difficulties were encountered in the conduct of population studies of the birds and mammals. Therefore, although site surveys of birds and mammals provide gross indications as to the presence and diversity of animals, it is probably more useful to rely on measures of residues and biomarkers to assess potential exposures and the possibility of subtle effects. Overall, it appears that ecological risk assessments at Superfund sites are best conducted by using a mix of predictive, laboratory, and field methods.

The Toxicology of Chemical Mixtures Risk Assessment for Human and Ecological Receptors

“…This uncertainty is frequently augmented by the extrapolation between test species and site receptors; often the extrapolation is based solely on bodyweight without consideration of additional physiological differences (Fairbrother, 2003). Uncertainty in the exposure assessment portion is compounded by sequential use of models to predict exposure concentrations and then to estimate bioaccumulation (Menzie et al, 1992). Toxicity of the congener mixture is estimated by the summation of toxic equivalents (George et al, 2003).…”

“…Biomonitoring may also include the gathering of exposure biomarkers; site mollusks, earthworms, birds or mammal populations can be sampled for tissue residues to determine if exposure pathways are complete or if bioaccumulation is occurring Menzie et aL, 1992;Smolders et aL, 2003). The measurement endpoint is assumed to infer a health effect to the population of concern.…”

Toxicological benchmarks for wildlife: 1995 revision

“…Contaminant concentrations in wildlife foods may need to be estimated using contaminant uptake models such as those described in Baes et al (1984), Travis and Arms (1988), or Menzies et al (1992). Table 13 provides a simplified example of the use of NOAELbased benchmarks in a screening assessment, The purpose of the assessment in this example is to identify the contaminants and media with concentrations sufficiently high to present a hazard to a representative endpoint species (meadow vole).…”

Work plan for conducting an ecological risk assessment at J-Field, Aberdeen Proving Ground, Maryland

“…In situ toxicity tests of earthworms (Menzie et al 1992) at upland locations (e.g., upgradient and downgradient of the pits and in pushout areas) may be used to determine the spatial pattern of potential soil toxicity if conditions of soil moisture allow.…”