Toxicity tests use specific aquatic and terrestrial microorganisms to measure biological response to specific contaminants or mixes of contaminants. The toxicity test measures the light output of luminescent microorganisms that emit light as a normal consequence of respiration. A luminometer reads the bacterial light output. Chemicals or chemical mixtures, which are toxic to the bacteria, cause a reduction in light output proportional to the strength of the toxin.
The Army has used a somewhat different approach to assess the effectiveness of various bio-treatment technologies at sites contaminated with high-explosive compounds. It used the Ames test and the Ceriodaphnia Dubia test to assess residual human health risk and ecological risk. To measure human health risk, the Ames test evaluates how much treatment reduces the mutagenic properties in Salmonella. To measure ecological risk, the Ceriodaphnia Dubia test assesses how much treatment reduces aquatic toxicity.
Limitations and Concerns
Matching specific microorganisms to specific contaminants in specific media is difficult.
The total toxicity of a sample can be readily measured, but the nature of the contaminant must still be determined by chemical analysis.
Temperature, pH, and handling may affect organisms/microorganisms, thus affecting results.
The two toxicity tests used by the Army can only be used as indicators of risk, but they should not be used to evaluate toxicity risk unless a full suite of toxicity tests are run in conjunction with them. These tests only provide limited information.
Toxicity tests using specific types of microorganisms can be used to assess high explosive compounds, semi volatile organic compounds (SVOCs), volatile organic compounds (VOCs), pesticides, metals and radionuclides. They are available to test soil, water and air.
Technology Development Status
The analytical methods are commercially available with moderate field experience.
Other Resources and Demonstrations
None identified except the Army’s test of two toxicity tests for the pilot-scale demonstration of the soil slurry bio-reactor (SSBR) at Joliet Army Ammunition Plant (JOAAP), and composting demonstration at the Umatilla Army Depot, in 1995 and 1992 respectively.