Advances to the CROSERF protocol to improve oil spill response decision making

Predicting the toxicity of physically and chemically dispersed oil: a modelling case study with American lobster larvae (Homarus americanus)

Determining the impact of an oil spill on aquatic ecosystems is a challenge. Because of the chemical complexity of crude oil, risk assessments rely on quantitative structure associated relationships to group chemical classes of compounds based on similar modes of toxicity. Quantitative structure associated relationships like the target lipid model can be used to determine species sensitivity by determining the critical target lipid body burden (CTLBB) and can be used to calculate the toxic units (TU) of a mixture. In this study we used the CTLBB generated from single polycyclic aromatic compound toxicity data and the analytical chemistry of whole oil to predicted and validate toxicity of both water-accommodated fraction (WAF) of crude oil and chemically dispersed WAF (CEWAF) to American lobster (Homarus americanus) larvae. A two-step procedure for modelling whole oil partitioning was utilized to compute the dissolved components in each of the WAF and CEWAF dilutions. Then, a species and life stage specific CTLBB derived for lobster larvae was applied in PetroTox to compute the TUs of exposure solution. The approach used in this study was able to effectively predict the effects observed in the exposures and can be integrated into oil spill fate and effects models to improve the oil spill assessment and response.

Parsing the toxicity paradox: Composition and duration of exposure alter predicted oil spill effects by orders of magnitude

Oil spilled into an aquatic environment produces oil droplet and dissolved component concentrations and compositions that are highly variable in space and time. Toxic effects on aquatic biota vary with sensitivity of the organism, concentration, composition, environmental conditions, and frequency and duration of exposure to the mixture of oil-derived dissolved compounds. For a range of spill (surface, subsea, blowout) and oil types under different environmental conditions, modeling of oil transport, fate, and organism behavior was used to quantify expected exposures over time for planktonic, motile, and stationary organisms. Different toxicity models were applied to these exposure time histories to characterize the influential roles of composition, concentration, and duration of exposure on aquatic toxicity. Misrepresenting these roles and exposures can affect results by orders of magnitude. Well-characterized laboratory studies for <24-hour exposures are needed to improve toxicity predictions of the typically short-term exposures that characterize spills.

Setting the stage to advance oil toxicity testing: Overview of knowledge gaps, and recommendations

The Chemical Response to Oil Spills: Ecological Effects Research Forum created a standardized protocol for comparing the in vivo toxicity of physically dispersed oil to chemically dispersed oil to support science-based decision making on the use of dispersants in the early 2000s. Since then, the protocol has been frequently modified to incorporate advances in technology; enable the study of unconventional and heavier oils; and provide data for use in a more diverse manner to cover the growing needs of the oil spill science community. Unfortunately, for many of these lab-based oil toxicity studies consideration was not given to the influence of modifications to the protocol on media chemistry, resulting toxicity and limitations for the use of resulting data in other contexts (e.g., risk assessments, models). To address these issues, a working group of international oil spill experts from academia, industry, government, and private organizations was convened under the Multi-Partner Research Initiative of Canada's Oceans Protection Plan to review publications using the CROSERF protocol since its inception to support their goal of coming to consensus on the key elements required within a "modernized CROSERF protocol".