Petroleum hydrocarbon mixture toxicity and a trait‐based approach to soil invertebrate species for site‐specific risk assessments

Abstract

Although petroleum hydrocarbons released to the environment typically occur as mixtures, petroleum hydrocarbon remediation guidelines often reflect individual substance toxicity. It is well documented that groups of aliphatic petroleum hydrocarbons act via the same mechanism of action (nonpolar narcosis) and, theoretically, concentration addition mixture toxicity principles apply. To assess this theory, 10 standardized acute and chronic soil invertebrate toxicity tests on a range of organisms (Eisenia fetida, Lumbricus terrestris, Enchytraeus crypticus, Folsomia candida, Oppia nitens, and Hypoaspis aculeifer) were conducted with a refined petroleum hydrocarbon binary mixture. Reference models for concentration addition and independent action were applied to the mixture toxicity data with consideration of synergism, antagonism, and dose level toxicity. Both concentration addition and independent action, without further interactions, provided the best fit with observed response to the mixture. Individual fraction effective concentration values were predicted from optimized, fitted reference models. Concentration addition provided a better estimate than independent action of individual fraction effective concentrations based on comparison with available literature and species trends observed in toxic responses to the mixture. Interspecies differences in standardized laboratory soil invertebrate species responses to petroleum hydrocarbon-contaminated soil was reflected in unique traits. Diets that included soil, large body size, permeable cuticle, low lipid content, lack of ability to molt, and no maternal transfer were traits linked to a sensitive survival response to petroleum hydrocarbon-contaminated soil in laboratory tests. Traits linked to sensitive reproduction response in organisms tested were long life span and small clutch size. By deriving single-fraction toxicity endpoints considerate of mixtures, we can reduce the resources and time required to conduct site-specific risk assessments for the protection of a soil organism's exposure pathway. Environ Toxicol Chem 2018;37:2222-2234. © 2018 SETAC.

Species Sensitivity to Toxic Substances: Evolution, Ecology and Applications

“…A key model assumption is that this concentration is species specific, rather than universal. Traits based studies have established differences in species responses based on lipid content, with low lipid levels linked to higher sensitivity, such as for petroleum hydrocarbons in soil invertebrates (Gainer et al, 2018) and the organophosphate fenitrothion in freshwater phytoplankton species, in which this pesticide likely exhibits narcotic toxicity (Kent and Currie, 1995). However, lipid composition currently provides only a partial explanation for the sensitivity indicated by the range of species-specific critical target lipid concentrations (Di Toro et al, 2000).…”

Bioaccumulation and Toxicity of Organic Chemicals in Terrestrial Invertebrates

“…Earthworms have generally proved lower sensitivity than collembolans but higher than enchytraeids. However, Gainer et al [177] showed greater sensitivity of earthworms to lubricating mixtures including PACs and aliphatic compounds probably related to a higher uptake due to their bigger size. Deviations from nonpolar narcosis might occur for sublethal endpoints, indicating that more specific responses might be present [178].…”

Oppia nitensC.L. Koch, 1836 (Acari: Oribatida): Current Status of Its Bionomics and Relevance as a Model Invertebrate in Soil Ecotoxicology

“…To understand how O. nitens interacts with soil contaminants, it is helpful to consider the impact of certain traits of this species, that is, its physiological, morphological, and ecological attributes (Baird and Van den Brink 2007). Specifically, 3 categories of traits are considered key to O. nitens' response to soil contamination: its body size and diet, intrinsic sensitivity, and life history characteristics (Van Straalen 1993;Rubach et al 2012;Gainer et al 2018).…”

“…Lipid content also influences the toxicity of organic contaminants. Based on findings from Gainer et al (2018), O. nitens, like other oribatid mites, has relatively high lipid contents compared with other standardized soil invertebrates in soil ecotoxicology (Table 2), which influences the partitioning of hydrophobic organic chemicals into organisms (Belfroid et al 1996 invertebrates (Table 2). For instance, based on evidence from aquatic invertebrate studies, maternal transfer could be another excretion route for O. nitens, especially for metals and organics (Keteles and Fleeger 2001;Conley et al 2009;Cid et al 2010).…”

“…In a study with petroleum hydrocarbon-contaminated soil (~250 000 mg/kg total petroleum hydrocarbon), Princz et al (2012) found no mortality of O. nitens; however, they observed that reproduction was substantially impacted relative to control. Gainer et al (2018) assessed the toxicity of lubricating oil, a 50/50 mixture of F2/F3 petroleum hydrocarbons, to O. nitens in OECD artificial soil (10% peat) and reported a reproduction EC50 value of 1210 mg/kg.…”