Design considerations to avoid bias in the construction of toxicity indices.
Species vary widely in their sensitivity to different toxicants. It is best to use a battery of toxicity tests, using organisms from very different trophic levels and taxonomic groups, to assess complex mixtures. The results of the various tests can then be collapsed into a toxicity index that will express the relative hazard of the different samples in a single number. As an example, a case study is presented to illustrate how decisions about the design of a toxicity index influence the ranking of effluents entering a large Canadian river. An index based on acute toxicity ranked municipal effluent as more toxic than pulp mill effluent, but when chronic tests were included the order reversed. Including the volume of discharge into the calculation caused another repositioning of the risk estimate for the two sources. This example illustrates the importance of clear objectives and precise construction of toxicity indices.
Taylor
Barry R
BR
Taylor Mazier Associates, St. Andrews, Nova Scotia, Canada. btaylor@auracom.com
D002170:Canada; D004785:Environmental Pollutants / Q000633:toxicity*; D007220:Industrial Waste / Q000009:adverse effects; D012722:Sewage / Q000009:adverse effects / Q000032:analysis; D014116:Toxicology / Q000592:standards*; D014874:Water Pollutants, Chemical / Q000633:toxicity
D004785:Environmental Pollutants; D007220:Industrial Waste; D012722:Sewage; D014874:Water Pollutants, Chemical