Recent Developments in Species Sensitivity Distribution Modeling

Abstract

The species sensitivity distribution (SSD) is a statistical approach that is used to estimate either the concentration of a chemical that is hazardous to no more than x% of all species (the HCx) or the proportion of species potentially affected by a given concentration of a chemical. Despite a significant body of published research and critical reviews over the past 20 yr aimed at improving the methodology, the fundamentals remain unchanged. Although there have been some recent suggestions for improvements to SSD methods in the literature, in general, few of these suggestions have been formally adopted. Furthermore, critics of the approach can rightly point to the fact that differences in technical implementation can lead to marked differences in results, thereby undermining confidence in SSD approaches. Despite the limitations, SSDs remain a practical tool and, until a demonstrably better inferential framework is available, developments and enhancements to conventional SSD practice will and should continue. We therefore believe the time has come for the scientific community to decide how it wants SSD methods to evolve. The present study summarizes the current status of, and elaborates on several recent developments for, SSD methods, specifically, model averaging, multimodality, and software development. We also consider future directions with respect to the use of SSDs, with the ultimate aim of helping to facilitate greater international collaboration and, potentially, greater harmonization of SSD methods. Environ Toxicol Chem 2021;40:293–308. © 2020 SETAC

Comparison of Species Sensitivity Distributions for Sediment‐Associated Nonionic Organic Chemicals Through Equilibrium Partitioning Theory and Spiked‐Sediment Toxicity Tests with Invertebrates

“…When a clear gap exists in the chemical sensitivity among different taxonomic groups, the use of a simple unimodal model may be problematic because of poor fitting in the left tail regions of the SSD (Fox et al, 2021). To address this, several methods have been proposed to estimate hazardous concentrations, such as using only the data from the most sensitive taxonomic groups (e.g., insects) or using a multimodal model (Del Signore et al, 2016; Fox et al, 2021; Nagai, 2016).…”

shinyssdtools: A web application for fitting Species Sensitivity Distributions (SSDs)

“…The species sensitivity distribution (SSD) is the most widely used method for getting water quality benchmarks to characterize effects of chemical contaminants for water quality or ecological risk assessment (Fox et al, 2020). This typically involves estimating the concentration of a chemical that affects 5% of the species considered (Posthuma et al, 2001).…”

“…This typically involves estimating the concentration of a chemical that affects 5% of the species considered (Posthuma et al, 2001). The ssdtools R package (Thorley & Schwarz, 2018) has recently advanced SSD methods by providing model averaging using information-theoretic criteria and the construction of confidence intervals using bootstrapping (Fox et al, 2020).…”

“…ssdtools is an R package that has provided recent advances in SSD methodology (Fox et al, 2020). shinyssdtools provides access to this functionality via a simple, modern GUI without requiring users to be familiar with the R programming language.…”

“…All historical and existing SSD software was recently reviewed by Fox et al (2020) who considered ssdtools, shinyssdtools and SSD Toolbox to be the most important contributions because they provide model averaging.…”