PM10 Assessing Toxicology: Critical Body Residue Approach
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM164) Effect of contaminant soil concentration and aging on earthworm critical body residues.
Johnson, K.1, Bhattarai, D.1, Friedel, C.1, 1 Southern Illinois University Edwardsville, Edwardsville, IL
ABSTRACT- Given the number of contaminated sites throughout the world we are in dire need of methods that will allow us to prioritize which sites should be remediated first. The prioritization should be based on the contaminant(s) of concern and their potential for risk. Confounding the issue is that the contaminant?s chemical properties and bioavailability change with time. Site assessments need to be based on bioavailable contaminant levels in soil rather than total soil concentrations. Conventional methods used to assess toxicity of contaminants are based on an organism?s exposure to total chemical concentrations and the corresponding mortality. This laboratory measure of toxicity has often times been criticized as an inadequate measure of a contaminant?s toxicity in the field due to many variable external factors. An approach that integrates the variability in a contaminant?s bioavailability in the field is desperately needed. One such approach is based on critical body residues (CBR) which are a measure of toxicity based on tissue residues in an organism at contaminated site. CBRs in organisms from the site of contamination may provide insight on the bioavailability of a chemical that can accumulate in the tissue of an organism regardless of external factors. This study investigated the effect of dieldrin?s soil concentration (11 concentrations) and the amount of time after fortification (aging) to that of an earthworm?s (Eisenia foetida) CBRs. Differences in dieldrin?s toxicity were observed between the fresh and aged soils with LD50s of 87 and 137 ?g dieldrin/g soil, respectively, suggesting contaminant aging does alter toxicity. However, CBRs remained constant for all soil concentrations at days 0 and 90. Critical body residues integrate all exposure routes, as well as the duration of exposure. As such CBRs may be a promising tool to assess contaminant toxicity and risk in field situations.
Key words: soil toxicity, critical body residue, aging, bioavailability