WP15 Soil Ecotoxicology and Risk Assessment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(AEL-1117-818936) Use of Microtox® to predict heavy metal concentrations in urban residential soils.

Aelion, C¹, Davis, H¹, ¹ University of South Carolina, Columbia, South Carolina, USA

ABSTRACT- Clusters of developmental delay and mental retardation (DD/MR) were identified in children born in Greenville County, South Carolina. Although it is difficult to identify one factor that causes the observed DD/MR outcome, exposure of pregnant women to environmental contaminants such as heavy metals can induce DD/MR in infants through a variety of pathways. Because it is impractical and expensive to measure the concentrations of individual metals in large numbers of environmental samples, the general toxicity test, Microtox® Toxicity System, was used to identify highly toxic soils. Approximately 200 soil samples were collected from residential areas in Greenville County and analyzed to determine an effective concentration (EC₅₀) of soil required to kill 50% of the luminescent bacteria test organisms (Vibrio fischeri). Lower EC₅₀ values denote greater toxicity. A subset of 56 high and low toxicity soil samples was then analyzed by inductively coupled plasma emission spectrophotometry for arsenic, lead, and chromium (EPA method 6010) which are known toxins. Significant negative correlations were found between the Microtox® EC₅₀ values and soil metal concentrations (-0.6022, p<0.0001 for arsenic; -0.6201, p<0.0001 for chromium; -0.3006, p=0.0244 for lead). The Microtox® test was effective in identifying soils with elevated concentrations of arsenic, chromium, and lead, even in residential neighborhoods where limited soil toxicity was expected. This screening tool appears to be a good surrogate for environmental exposure and a first step for quantifying environmental exposure and determining its possible association with DD/MR in these children.

Key words: heavy metals, soil contamination, environmental exposure, Microtox®