Development and Application of an Oil Toxicity and Exposure Model, Oiltoxex

Self Cite

137

An oil toxicity and exposure model (OilToxEx) was developed and validated for estimation of impacts to aquatic organisms resulting from acute exposure to spilled oil. Because oil exposure is shorter than the time required for equilibrium between the organism and the water to be reached, the time and temperature dependence of toxicity is addressed. Oil toxicity is a function of aromatic composition and the toxicity of individual aromatics in the mixture. Lethal concentration to 50% of exposed organisms (LC50), as a function of octanol-water partition coefficient (Kow), and an additive model are used to estimate the toxicity of monoaromatic and polycyclic aromatic hydrocarbon mixtures in water-soluble fractions (WSF) and oil-in-water dispersions (OWD) of oil. The toxicity model was verified by comparison with oil bioassay data where the exposure concentrations of aromatics were measured. The observed toxicity in the bioassays could be accounted for by the additive narcotic effects of the dissolved aromatics in the exposure media. Predicted LC50s were compared to those calculated from measured concentrations after spills to verify the exposure model for field conditions. These results indicate that the additive toxicity and exposure model may be used to estimate toxicity of untested oils and spill conditions.

Section: Resultssupporting

confidence: 59%

“…A total of 278 MAH and PAH LC50 estimates were obtained from the literature, 115 for fish, 129 for crustaceans, and the remainder (34) for other invertebrates [74]. Forty‐one species are represented in the data set.…”

Section: Resultsmentioning

confidence: 99%

Development and application of an oil toxicity and exposure model, OilToxEx

French-McCay

2002

Self Cite

137

“…This is an important observation, because often, only the aromatic component, specifically BTEX, is considered when assessing aquatic toxicity hazards from gasoline. The situation is similar for oils, in which dissolved aromatics are believed to be the main components responsible for toxicity [36]. Barron et al [37] demonstrated that PAHs were not the majority determinant for the toxicity of three middle‐distillate oils to mysid shrimp in laboratory tests.…”

Section: Resultsmentioning

confidence: 99%

Validation of the narcosis target lipid model for petroleum products: Gasoline as a case study

McGrath¹,

Parkerton

Hellweger

et al. 2005

The narcosis target lipid model (NTLM) was used to predict the toxicity of water-accommodated fractions (WAFs) of six gasoline blending streams to algae (Pseudokirchnereilla subcapitata, formerly Selenastrum capricornutum), juvenile rainbow trout (Oncorhynchus mykiss), and water flea (Daphnia magna). Gasolines are comprised of hydrocarbons that on dissolution into the aqueous phase are expected to act via narcosis. Aquatic toxicity data were obtained using a lethal-loading test in which WAFs were prepared using different gasoline loadings. The compositions of the gasolines were determined by analysis of C3 to C13 hydrocarbons grouped in classes of n-alkanes, iso-alkanes, aromatics, cyclic alkanes, and olefins. A model was developed to compute the concentrations of hydrocarbon blocks in WAFs based on gasoline composition and loading. The model accounts for the volume change of the gasoline, which varies depending on loading and volatilization loss. The predicted aqueous composition of WAFs compared favorably to measurements, and the predicted aqueous concentrations of WAFs were used in the NTLM to predict the aquatic toxicity of the gasolines. For each gasoline loading and species, total toxic units (TUs) were computed with an assumption of additivity. The acute toxicity of gasolines was predicted to within a factor of two for algae and daphnids. Predicted TUs overestimated toxicity to trout because of experimental factors that were not considered in the model. This analysis demonstrates the importance of aliphatic hydrocarbon loss to headspace during WAF preparation and the contribution of both aromatic and aliphatic hydrocarbons test to the toxicity of gasolines in closed systems and loss of aliphatics to headspace during WAF preparation. Model calculations indicate that satisfactory toxicity predictions can be achieved by describing gasoline composition using a limited number of aromatic and aliphatic hydrocarbon blocks with different octanol-water partition coefficients.

“…Toxicity testing data from laboratory studies have facilitated our understanding of the effects of oil and oil constituents on a diverse number of aquatic species. This information has been reviewed by the US National Academy of Sciences, the American Petroleum Institute, the National Oceanic and Atmospheric Administration, and other institutions and scientists facilitating the development of useful benchmarks that help inform decision makers . However, shortcomings are inherent in the use of standard laboratory toxicity data to assess the effects to water column biota from chemically treated oil spills, as well as to support management decisions on the offshore use of dispersants.…”

Section: Introductionmentioning

confidence: 99%

Issues and challenges with oil toxicity data and implications for their use in decision making: A quantitative review

Bejarano¹,

Clark²,

Coelho³

2014

Aquatic toxicity considerations are part of the net environmental benefit analysis and approval decision process on the use of dispersants in the event of an offshore oil spill. Substantial information is available on the acute toxicity of physically and chemically dispersed oil to a diverse subset of aquatic species generated under controlled laboratory conditions. However, most information has been generated following standard laboratory practices, which do not realistically represent oil spill conditions in the field. The goal of the present quantitative review is to evaluate the use of standard toxicity testing data to help inform decisions regarding dispersant use, recognizing some key issues with current practices, specifically, reporting toxicity metrics (nominal vs measured), exposure duration (standard durations vs short-term exposures), and exposure concentrations (constant vs spiked). Analytical chemistry data also were used to demonstrate the role of oil loading on acute toxicity and the influence of dispersants on chemical partitioning. The analyses presented here strongly suggest that decisions should be made, at a minimum, based on measured aqueous exposure concentrations and, ideally, using data from short-term exposure durations under spiked exposure concentrations. Available data sets are used to demonstrate how species sensitivity distribution curves can provide useful insights to the decision-making process on dispersant use. Finally, recommendations are provided, including the adoption of oil spill-appropriate toxicity testing practices. Environ Toxicol Chem 2014;33:732-742. # 2014 SETAC