In order to simulate an offshore oil spill event, we assessed the acute toxicity of the non-dispersed and the chemically dispersed water-accommodated fraction (WAF) of crude oil using Louisiana sweet crude and Corexit(®) 9500A with juvenile Harris mud crabs (Rhithropanopeus harrisii), an important Gulf of Mexico benthic crustacean. The chemical dispersion of crude oil significantly increased acute toxicity of the WAF in juvenile mud crabs compared to naturally dispersed oil. The majority of the mortality in the chemically dispersed treatments occurred within 24 h. While higher concentrations of chemically dispersed WAF had no survivors, at lower concentrations surviving juvenile crabs displayed no long-term effects. These results suggest that if the juvenile crabs survive initial exposure, acute exposure to dispersed or non-dispersed crude oil may not induce long-term effects.
Chemical dispersants are an important technology in the remediation of oil spills in the aquatic environment, facilitating degradation of crude oil and salinity is an important factor in dispersant effectiveness. The aim of the present study was to explore the role of salinity on the degradation chemistry of crude oil polycyclic aromatic hydrocarbons (PAHs) and acute toxicity of the wateraccommodated fraction (WAF) of the dispersant COREXIT 9500A and chemically dispersed crude oil on a common estuarine fish. Laboratory microcosms were designed at salinities of 4 parts per thousand (ppt), 12 ppt, or 18 ppt and spiked with crude oil, COREXIT 9500A, or a combined exposure to crude oil and COREXIT and allowed to biodegrade for 1 wk, 4 wk, and 16 wk. The WAF was harvested for analytical PAH analysis and acute toxicity testing in juvenile Fundulus grandis. Compared with undispersed oil, COREXIT exponentially increased the PAH concentrations in the WAF for up to 16 wk; hopane-normalized concentrations indicated that biodegradation was slowed for the first 4 wk. Dispersed crude oil and COREXIT were acutely toxic following 1 wk of biodegradation with no correlation between PAH concentrations and crude oil WAF mortality. Both dispersant and dispersant oil mixtures remained toxic for at least 4 wk at the lowest salinity tested, suggesting increased sensitivity or reduced biodegradation of toxic components in low-saline environments. At the lowest salinity, oil dispersed with COREXIT was more toxic than either the COREXIT alone or oil alone, even after 16 wk of biodegradation. Environ Toxicol Chem 2013;32:2611-2620. # 2013 SETAC
Naphthenic acids (NAs) are primarily cycloaliphatic carboxylic acids with 10 to 16 carbons. To characterize the potential of refined NAs (>70% purity) to cause reproductive and/or developmental effects, Sprague-Dawley rats (12/group) were given oral doses of 100, 300, or 900 mg/kg/d, beginning 14 days prior to mating, then an additional 14 days for males or through lactation day 3 for females (up to 53 days) in a repeated dose/reproductive toxicity test (Organization for Economic Cooperation and Development [OECD] 422). Potential mutagenic effects were assessed using Salmonella (OECD 471) and in in vivo micronucleus tests (OECD 474) using bone marrow taken from treated animals in the screening study described previously. Systemic effects included reduced terminal body weights, increased liver weights, and changes in a number of blood cell parameters. The overall no effect level for all target organ effects was 100 mg/kg/d. In the reproductive/developmental toxicity assessment, there were significant reductions in numbers of live born offspring in groups exposed to 300 and 900 mg/kg/d. The overall no effect level for developmental effects was 100 mg/kg/d. The data from the Salmonella and micronucleus tests provide evidence that refined NAs are not genotoxic.
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