James R Wheeler | PubMed Health

PubMed2002

Better bootstrap estimation of hazardous concentration thresholds for aquatic assemblages.

The introduction of species sensitivity distribution (SSD) approaches to ecological risk assessment offers the potential for a more transparent scientific basis for the derivation of predicted no-effect concentrations. However, conventional SSD methodologies have relied on standard distributions (e.g., log logistic, log normal) that are not necessarily based on sound ecological or statistical grounds. More recently, bootstrap resampling techniques that do not rely on distributional assumptions have been applied to the problem. Here we describe how a more advanced bootstrap methodology may be applied to derive better point estimates and confidence intervals for SSD estimates of safe environmental concentrations. Motivated by the fact that the true SSD may not fit any standard model category, we go on to consider a hybrid bootstrap regression approach. This can yield a substantially different estimate for the SSD when compared with both the basic bootstrap and the more frequently used parametric curve approaches. With increasing use of SSDs in ecological risk assessment, it is now imperative that the scientific community develops agreement over appropriate methods for their derivation.

Data Interpretation, Statistical↗

PubMed2002

Freshwater to saltwater toxicity extrapolation using species sensitivity distributions.

There is generally a lack of saltwater ecotoxicity data for risk assessment purposes, leaving an unknown margin of uncertainty in saltwater assessments that utilize surrogate freshwater data. Consequently, a need for sound scientific advice on the suitability of using freshwater data to extrapolate to saltwater effects exists. Here we use species sensitivity distributions to determine if freshwater datasets are adequately protective of saltwater species assemblages for 21 chemical substances. For ammonia and the metal compounds among these data, freshwater data were generally protective because freshwater organisms tended to be more sensitive. In contrast, for pesticide and narcotic compounds, saltwater species tended to be more sensitive and a suitable uncertainty factor would need to be applied to surrogate freshwater data. Biological and physicochemical factors contribute to such differences in freshwater and saltwater species sensitivities, but the species compositions of datasets used are also important.

Animals↗