Estimating the 5-Percentile of the Species Sensitivity Distributions Without Any Assumptions about the Distribution
A non-parametric method is described to estimate the hazardeous concentration for p% of the species, the HCp, and the confidence limits for this value, the HCp(α). For this method, all observed sensitivities are ordered from high to low sensitivity. The HC5 is the k-th observation were k is the largest integer below 0.05×(n+1). It is described how the HCp(α) can be calculated. A table is presented for easy calculation of several conservative confidence limits for the HC5. For the HC5(0.05), a second table is presented which can be used to interpolate between the conservative estimate of the HC5(0.05) and the next higher observed concentration. The non-parametric HC5 and HC5(0.05) estimation is illustrated with an example of sensitivity data on malathion. For this data set, the log-normal HC5 and HC5(0.05) estimations appear to be conservative compared with the non-parametric estimate. It is stressed that HC5 and HC5(0.05) estimates will often be much more affected by the non-randomness of the species set for which sensitivity data are available than by the choice of the statistical method.
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- Aldenberg, T. and Slob, W. (1993). Confidence limits for hazardous concentrations based on the logistically distributed NOEC toxicity data. Ecotoxicol. Enυiron. Saf. 25, 48–63.Google Scholar
- Jagoe, R.H. and Newman, M.C. (1997). Bootstrap estimation of community NOEC values. Ecotoxicology 6, 293–306.Google Scholar
- Kooijman, S.A.L.M. (1987). A safety factor for LC50 values allowing for differences in sensitivity among species. Water Res. 21, 269–76.Google Scholar
- Newman, M.C., Ownby, D.R., Mezin, L.C.A., Powell, D.C., Christensen, T.R.L., Lerberg, S.B. and Anderson, B.A. (2000). Applying species sensitivity distributions in ecological risk assessment: assumptions of distribution type and sufficient number of species. Enυiron. Toxicol. Chem. 19, 508–15.Google Scholar
- van Straalen, N.M. and Denneman, C.A. (1989). Ecotoxicological evaluation of soil quality criteria. Ecotoxicol. Enυiron. Saf. 18, 241–51.Google Scholar
- Wagner, C. and Løkke, H. (1991). Estimation of ecotoxicological protection levels for NOEC toxicity data. Water Res. 25, 1237–42.Google Scholar