Application of bioassays for toxicity screening

2 Application of bioassays for toxicity screening Bioassays used as screening tools aim at the identification of toxic samples. Short test duration, sensitivity, reliability and ease of use are favourable characteristics for test selection. Screening test applications include  

One step in assessment of a contaminated site is the determination of the spatial extent and distribution of the contamination. For heterogeneous pollution, screening tests may determine hot spots and areas with no or low toxicity within a short time period at reasonable cost. However, if historical data provide sufficient information on the type of contamination, then chemical analysis may be preferable when focusing on single toxicants or simple groups of toxicants (e.g. BTEX) ecotoxicological information can be ascertained from literature or databases. 

Remediation aims at the reduction of risk. The disappearance of native pollutants during remediation does not necessarily result in a reduction of risk. Screening tests may be valuable monitoring tools to evaluate remediation measures as they may indicate, for example, an undesirable formation of toxic intermediates or an unwanted increase of pollutant mobility. 

False negative results. The detection of no effects for toxic samples may have the following reasons  

Insufficient sensitivity is the most relevant factor, others are considered to reduce toxicity responses but are hardly able to totally mask toxicity. Estimation of the probability of obtaining false negative results will help to decide whether further investigation is required. 

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