Understanding single‐species and model ecosystem sensitivity: Data‐based comparison

Abstract

Abstract-Risk assessments for compounds released to the environment typically rely on single-species toxicity studies to predict concentrations at which effects may be observed. These single-species toxicity studies are usually conducted with a few species, cultured under optimum conditions (diet, temperature, light, etc.) and tested in clean water with constant exposure to the compound of interest. Chronic toxicity data are then extrapolated to the ecosystem during risk assessments to predict concentrations that will not adversely impact the environment. Several approaches have been developed that apply statistical methods to estimate toxicant concentrations adversely affecting a small percentage of single species (e.g., 5%). There are several rarely stated, and infrequently tested, biological and statistical assumptions required to make this extrapolation. One test of the ability to use single-species toxicity data to protect ecosystems is to compare effects on single species with effects on experimental and natural ecosystems (e.g., microcosms, model ecosystems, field). Towards this end, we summarized the chronic single-species and experimental ecosystem data on a variety of substances (n ϭ 11), including heavy metals, pesticides, surfactants, and general organic and inorganic compounds. Single-species data were summarized as genus-specific geometric means using the NOEC or EC20 concentration.Genus mean values spanned a range of values with genera being affected at concentrations above and below those causing effects on model ecosystems. Geometric mean model ecosystem no effect concentrations corresponded to concentrations expected to exceed the NOEC of 10 to 52% of genera. This analysis suggests that laboratory-generated single-species chronic studies can be used to establish concentrations protective of model ecosystem, and likely whole ecosystem, effects. Further, the use of the 5% of genera affected level is conservative relative to mean model ecosystem data but is a fairly good predictor of the lower 95% confidence interval on the mean model ecosystem NOEC.

Aquatic Risks of Pesticides, Ecological Protection Goals, and Common Aims in European Union Legislation

“…Studies of other pesticides that compared threshold concentrations for direct toxic effects as a result of chronic exposure between model ecosystem experiments are not known to us. However, evidence suggests that threshold concentrations for chronic exposure to the surfactant dodecyl trimethyl ammonium chloride do not differ much between model stream experiments (range of NOEC ecosystem values, 180-300 lg/L; n ¼ 5; Versteeg et al 1999). Similarly, only a 3-fold difference in threshold concentrations is reported for long-term exposure to copper (hardness adjusted to 50 mg/L as CaCO 3 ) derived from 1 lentic mesocosm and 6 artificial stream studies conducted in the United States and Europe (Versteeg et al 1999).…”

Comparing Sensitivity of Ecotoxicological Effect Endpoints between Laboratory and Field

“…Risk assessment of toxic compounds released to the aquatic environment is mostly based on results extrapolated from single-species (SS) laboratory tests using algae, daphnids, and "sh (e.g., Rand and Petrocelli, 1985;OECD, 1992;Zeeman and Gilford, 1993;Forbes and Forbes, 1993;van Leeuwen, 1996b), where the measured endpoints generally include survival, growth, and reproduction (Versteeg et al, 1999). Available toxicity data may include L(E)C , which is the concentration of toxicant that causes lethality (L) or e!ect (E) in 50% of an exposed population, or the concentration in a concentration}response experiment that does not cause a stastically detectable e!ect: no-observede!ect concentration (NOEC).…”

“…The most commonly used distribution models assume a log-normal (Wagner and L+kke, 1991) or log-logistic (Aldenberg and Slob, 1993) distribution of NOEC values for di!erent species. Several biological and statistical assumptions are implied in the SSD models to make the extrapolation from laboratory tests to e!ects at the ecosystem level including the assumptions that (1) the variability in the sensitivity of the laboratory test species is similar to the variability among the species for which one aims to assess risk, (2) the endpoints measured in laboratory tests are indicative of e!ects on populations in the "eld, and (3) the estimated toxicant concentration, at which the NOECs of, generally, 95% of the species are not exceeded, protects ecosystem structure and function to an appropriate degree (Versteeg et al, 1999). However, in practice neither the assessment factor approach nor the SSD approach consistently ful"lls these assumptions (Forbes and Calow, 2002).…”

LCA-measured environmental improvements in Pampers® diapers

“…For decades, P&G has worked collaboratively with government, academic, and other industry scientists to develop the methods and assessments to understand and improve both the environmental safety, and life cycles of products that people use every day (Bradbury et al 2004;Cowan et al 1995;Cowan-Ellsberry et al 2004;de Koning et al 2010;Fava et al 1991;Pittinger et al 1991;Saouter et al 2002;van de Plassche et al 1999;Versteeg et al 1999 Fava et al 1990;Franklin and Ltd 1992;Lentz et al 1989;MRI Project No. 3746-D 1974;Nylander 1991;Sandgren 1993;Sauer et al 1994;UK Environment Agency 2005, 2008Vizcarra et al 1994).…”