Grantee Research Project Results
Examination of Stormwater Toxicity Using the Microtox Bioassy
EPA Grant Number: U915005Title: Examination of Stormwater Toxicity Using the Microtox Bioassy
Investigators: Youngblood, Cecelia L.
Institution: University of Illinois Urbana-Champaign
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1996 through January 13, 1998
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1996) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology
Objective:
The objectives of this research project are to: (1) measure the toxicity of low concentrations of binary and complex mixtures of contaminants using the Microtox bioassay; and (2) determine if pollutant mixtures at low concentrations are responsible for inducing the high levels of hormesis (stimulation of activity when organisms are exposed to low levels of toxics) previously measured in stormwater samples.
Approach:
Experimentation will be conducted in two phases: binary mixture experiments and stormwater simulation experiments.
Phase 1. The Microtox screening test will be used to test pairs of metals, organic chemicals, and metal-organic combinations. A 5x5 matrix of concentrations will be used for each binary combination, resulting in 25 treatments for each pair of toxicants. Each 5x5 matrix will be replicated three times using a different lot of reagent for each replication to account for biological variability. All Microtox testing will be performed according to standard procedures recommended by Azure Corporation. Because the toxicity of mixtures may be affected by temperature, each experiment will be replicated three times at both 15°C and 23°C. Five metals and five organic chemicals will be selected for study from the following list: cadmium, chromium, lead, nickel, zinc, phenol, sodium laurel sulfate, 1-octano, benzene, acetone, ethylene glycol, atrazine, acetaldehyde, diethylene glycol. The substances chosen represent common environmental contaminants and a range of functional groups. Appropriate hormesis-inducing concentrations of each toxicant will be determined prior to the matrix experiments through the construction of individual dose-response curves.
Phase 2. After the binary combination experiments have been completed, various combinations of toxicants (mixtures containing > 2 toxicants) will be created. Previous Microtox screening tests performed on stormwater samples resulted in stimulation as high as 60 percent; however, no individual toxicant concentration has ever stimulated such a large percent effect. Using the data collected in Phase 1, combinations of chemical groups will be tested to produce high levels of stimulation. Due to the enormous number of combinations that a factorial design would require, only selected mixtures will be analyzed. Some selected mixtures will have toxicant concentrations based on actual concentrations measured in collected stormwater samples.