Assessments of Chemical Mixtures via Toxicity Reference Values Overpredict Hazard to Ohio Fish Communities

Abstract

A diverse array of environmental data from Ohio were placed into a geographical information system (GIS). This GIS allowed for the investigation of approaches and paradigms currently advocated for ecological risk assessment. The paradigm of chemical mixture additivity was investigated in this project. Toxic units (toxic unit ) concentration of a chemical in an organism/chemical concentration causing a specified effect) for 12 organic and 11 metal contaminants were calculated from 2878 fish samples collected at 1010 sites throughout the state of Ohio. Additive analysis of TUs for organic chemicals based on regulatory-based protective limits (toxicity reference value ) USEPA water quality criterion*bioconcentration factor) overpredicted adverse effects to individual fish and fish communities. However, addition of organic chemical molar units did not overpredict adverse effects, thus, supporting the concept of baseline toxicity. Molar units of organic chemicals with diverse modes of action may be added together, so long as they are at concentrations below levels deemed protective of most species (e.g., 95%, water quality criterion). Analysis of metal TUs benchmarked against regulatorybased limits overpredicted adverse effects, whereas benchmark concentrations from population response (survival, growth, reproduction) data from the literature and Ohio reference site fish community responses corresponded better to field observations. Of the factors analyzed, habitat quality is the best single predictor of fish community integrity in Ohio, not body burdens of metals or organic chemicals.

The Toxicology of Chemical Mixtures Risk Assessment for Human and Ecological Receptors

“…Toxicity of related chemicals or those having the same mode of action can be summed using additivity or dose addition (ECETOC, 2001;Escher and Hermens, 2002). Additivity has been confirmed in various species for PAHs, triazine congeners, BTEX (benzene, toluene, ethylbenzene and xylenes) and many metals (Ankley and Mount, 1996;Dyer et at, 2000;Faust et a!, 2000;Niederlehner eta!, 1998;Ross and Bidwell, 2003;Vighi and Calamari, 1996). Additivity occurs even when components are present below the individual chemical lowest observable effect concentrations (LOECs).…”

“…The effects are reversible, provided the membrane concentration fails to reach the internal effect threshold; this threshold is specific to species, size (surface:volume ratio), lipid content and other factors (Altenburger et al, 2003;Escher and Hermens, 2002). Most organic compounds have specific toxicity at higher concentrations but low levels can result in non-specific effects (Dyer et at., 2000;Niederlehner et at., 1998).…”

“…At some sites, unexpected acute toxicity results from pulsatile releases. Storm event sampling methods may be employed to capture these exposure levels (Dyer et aL, 2000).…”

“…Metal exposure may not equate with toxicity at the site due to species adaptation to the background. This can result in overprediction of toxicity not correlated with site field assessments (e.g., index of biotic integrity) (Dyer et al, 2000).…”

Physicochemical tolerance ranges and ecological characteristics in two different populations of Carassius auratus and Cyprinus carpio

“…For these reasons, the United morphology (Wang et al 2003), and flow regime (Bunn and Arthington 2002) are known to be important factors influencing the level of fish tolerance in aquatic ecosystems. Also, chemical parameters such as organic matter pollutant (Dyer et al 2000), toxic chemicals (Brian et al 2005), ionic content or salinity (Le François et al 2004) or nutrients (N, P) are other key factors that control fish tolerance in the waterbodies of geographic regions. In addition, fish tolerance may also be associated with biological factors such as predation (Brown et al 2005).…”