Corexit Research Articles

Chemical dispersant potentiates crude oil impacts on growth, reproduction, and gene expression in Caenorhabditis elegans

The economic, environmental, and human health impacts of the deepwater horizon (DWH) oil spill have been of significant concern in the general public and among scientists. This study employs parallel experiments to test the effects of crude oil from the DWH oil well, chemical dispersant Corexit 9500A, and dispersant-oil mixture on growth and reproduction in the model organism Caenorhabditis elegans. Both the crude oil and the dispersant significantly inhibited the reproduction of C. elegans. Dose-dependent inhibitions of hatched larvae production were observed in worms exposed to both crude oil and dispersant. Importantly, the chemical dispersant Corexit 9500A potentiated crude oil effects; dispersant-oil mixture induced more significant effects than oil or dispersant-alone exposures. While oil-alone exposure and dispersant-alone exposure have none to moderate inhibitory effects on hatched larvae production, respectively, the mixture of dispersant and oil induced much more significant inhibition of offspring production. The production of hatched larvae was almost completely inhibited by several high concentrations of the dispersant-oil mixture. This suggests a sensitive bioassay for future investigation of oil/dispersant impacts on organisms. We also investigated the effects of crude oil/dispersant exposure at the molecular level by measuring the expressions of 31 functional genes. Results showed that the dispersant and the dispersant-oil mixture induced aberrant expressions of 12 protein-coding genes (cat-4, trxr-2, sdhb-1, lev-8, lin-39, unc-115, prdx-3, sod-1, acr-16, ric-3, unc-68, and acr-8). These 12 genes are associated with a variety of biological processes, including egg-laying, oxidative stress, muscle contraction, and neurological functions. In summary, the toxicity potentiating effect of chemical dispersant must be taken into consideration in future crude oil cleanup applications.

Response of larval frogs to Corexit 9500

The use of dispersants in the Gulf of Mexico has created a number of environmental and human health concerns, chief among them are questions regarding the potential impact of Corexit 9500 on the health and fitness of Gulf wildlife. These studies were designed to use a biological toxicity test during post-fertilization and early development to evaluate Corexit 9500A effect on The Frog Embryo Teratogenesis Assay-Xenopus (FETAX) assay. Frog embryos were exposed to concentrations ranging from 1000 to 1 uL L−1 for Corexit 9500 A. Various forms of malformations were recorded following exposure to Corexit 9500. These abnormalities included pharyngeal and thoracic edema, severe optic edema, and incomplete and reversed gut coiling. The percent of males was higher in the Corexit-treated groups, while control was closer to the expected 50:50 males to females ratio. In addition, a statistically greater number of hypomelanistic animals were observed in the Corexit-treated animals versus controls. Exposure of early life stage frogs to dispersants may exert chronic effects on health status of adults and as such consideration and evaluation of Corexit exposure to vulnerable life stages needs to be given high priority in the determination of risk and long-term impact and recovery of the ecosystem.

Lung epithelial cell death induced by oil-dispersant mixtures

The dispersants used in oil spill disasters are claimed to be safe, but increased solubility of high-molecular-weight components in crude oil is of public health concern. The water-accommodated fractions (WAF) of crude oil mixed with dispersants may become airborne and cause lung epithelial damage when inhaled. This study was designed to examine the cell death and related death pathways of lung epithelial cells in response to WAF. Cultured A549 cells were treated for 2 or 24h with different concentrations of WAF. The WAF was prepared by mixing each of the dispersants (Corexit EC9527A, Corexit EC9500A and Corexit EC9580A) with crude oil for extraction with PBS. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay, lactate dehydrogenase assay, morphology and cleaved caspase 9 protein, and microtubule-associated protein 1 light chain 3 were all used to measure cell viability, necrosis, apoptosis and autophagy quantitation, respectively. Results showed that the WAF of oil-dispersant mixtures caused cell death in the lung epithelial cells, in a dose-dependent manner, with the major cellular pathways of necrosis and apoptosis involved. Autophagy also occurred in cells exposed to WAF mixtures at lower concentrations before any detectable cell death, indicating greater sensitivity to WAF exposure. The three types of cell behavior, namely necrosis, apoptosis and autophagy, may play different roles in oil spill-related respiratory disorders.

In vitro toxicity screening of chemical mixtures using HepG2/C3A cells

Traditional toxicological methods that utilize only single pure compounds may not accurately predict risks from substances with multiple chemical constituents. A complementary approach to conventional methodologies includes in vitro systems that assess toxicity of chemical mixtures and identify components that may adversely impact biological processes. Compared to animal models, in vitro assays are inexpensive, rapid, and reduce and refine related animal testing. We utilized HepG2/C3A cells as a hepatotoxicity screening model to evaluate the cytotoxic and metabolic effects of three commercially available oil dispersants, Corexit EC9500A and EC9527A and ZI-400. The surfactant DOSS, a primary active constituent of the Corexit dispersants, was also evaluated. Biologically relevant endpoints were measured including cell viability, oxidative stress, and mitochondrial activity. Significant increases in cytotoxicity were observed with Corexit dispersants (LC50∼250ppm), whereas ZI-400 was moderately cytotoxic (LC50 >>400ppm). Each dispersant caused an accumulation of reactive oxygen species and altered mitochondrial activity and other cellular processes. Generally, DOSS made notable contributions to the effects of EC9500A and EC9527A, however, they were observed at concentrations higher than those used in most consumer products. Overall, this system may represent a valuable complementary tool for predicting the toxicity of complex mixtures.

Investigating the effectiveness of the surfactant dioctyl sodium sulfosuccinate to disperse oil in a changing marine environment

We investigated the surfactant dioctyl sodium sulfosuccinate (DOSS) and its delivery system Corexit 9500A, used to disperse oil released during the Gulf of Mexico spill during the summer of 2010. DOSS is an organic sulfonic acid salt that acts as a synthetic detergent and disrupts the interfacial tension between the salt water and crude oil phases. The disruption reaches a maximum at or above the critical micelle concentration (CMC). The CMC for the surfactant was determined to be 0.17% solution in deionized water at a pH of 7.2 and a temperature of 21.1 °C (70°F). The CMC is lower in salt water, at 0.125% solution. This has been identified as a “salting out” effect (Somasundaran, 2006). The CMC of DOSS in both saline and deionized water occurred at lower-percent solutions at higher temperatures. The surface tension versus concentration plots can be modeled using a power equation, with correlation coefficients consistently over 0.94. Surface tension versus concentration plots are scalable to fit the desired temperature by the function f(x) = (1/1+Xα), where α =T1/T2. Tests measured the stability of the DOSS micelles when exposed to a continuous UVA radiation. This photodegradation is directly related to the duration of exposure.

Potential Immunotoxicological Health Effects Following Exposure to COREXIT 9500A during Cleanup of the Deepwater Horizon Oil Spill

Workers involved in the Deepwater Horizon oil spill cleanup efforts reported acute pulmonary and dermatological adverse health effects. These studies were undertaken to assess the immunotoxicity of COREXIT 9500A, the primary dispersant used in cleanup efforts, as a potential causative agent. COREXIT 9500A and one of its active ingredients, dioctyl sodium sulfosuccinate (DSS), were evaluated using murine models for hypersensitivity and immune suppression, including the local lymph node assay (LLNA), phenotypic analysis of draining lymph node cells (DLN), mouse ear swelling test (MEST), total serum immunoglobulin E (IgE), and the plaque-forming cell (PFC) assay. Dermal exposure to COREXIT 9500A and DSS induced dose-responsive increases in dermal irritation and lymphocyte proliferation. The EC3 values for COREXIT 9500A and DSS were 0.4% and 3.9%, respectively, resulting in a classification of COREXIT 9500A as a potent sensitizer and DSS as a moderate sensitizer. A T-cell-mediated mechanism underlying the LLNA was supported by positive responses in the MEST assay for COREXIT and DSS, indicated by a significant increase in ear swelling 48 h post challenge. There were no marked alterations in total serum IgE or B220+/IgE+ lymph-node cell populations following exposure to COREXIT 9500A. Significant elevations in interferon (IFN)-γ but not interleukin (IL)-4 protein were also observed in stimulated lymph node cells. The absence of increases in IgE and IL-4 in the presence of enhanced lymphocyte proliferation, positive MEST responses, and elevations in IFN-γ suggest a T-cell-mediated mechanism. COREXIT 9500A did not induce immunosuppression in the murine model.

A Computer-Controlled Whole-Body Inhalation Exposure System for the Oil Dispersant COREXIT EC9500A

An automated whole-body inhalation exposure system capable of exposing 12 individually housed rats was designed to examine the potential adverse health effects of the oil dispersant COREXIT EC9500A, used extensively during the Deepwater Horizon oil spill. A computer-controlled syringe pump injected the COREXIT EC9500A into an atomizer where droplets and vapor were formed and mixed with diluent air. The aerosolized COREXIT EC9500A was passed into a customized exposure chamber where a calibrated light-scattering instrument estimated the real-time particle mass concentration of the aerosol in the chamber. Software feedback loops controlled the chamber aerosol concentration and pressure throughout each exposure. The particle size distribution of the dispersant aerosol was measured and shown to have a count median aerodynamic diameter of 285 nm with a geometric standard deviation of 1.7. The total chamber concentration (particulate + vapor) was determined using a modification of the acidified methylene blue spectrophotometric assay for anionic surfactants. Tests were conducted to show the effectiveness of closed loop control of chamber concentration and to verify chamber concentration homogeneity. Five automated 5-h animal exposures were performed that produced controlled and consistent COREXIT EC9500A concentrations (27.1 ± 2.9 mg/m3, mean ± SD).

Acute Effects of COREXIT EC9500A on Cardiovascular Functions in Rats

These studies characterized cardiovascular responses after an acute inhalation exposure to COREXIT EC9500A, the oil dispersant used in the Deepwater Horizon oil spill. Male Sprague-Dawley rats underwent a single 5-h inhalation exposure to COREXIT EC9500A (average exposure level 27.12 mg/m3) or air. On d 1 and 7 following the exposure, rats were implanted with indwelling catheters and changes in heart rate and blood pressure were assessed in response to increasing levels of adrenoreceptor agonists. A separate group of rats was euthanized at the same time points, ventral tail arteries were dissected, and vascular tone along with dose-dependent responses to vasoconstricting and dilating factors were assessed in vitro. Agonist-induced dose-dependent increases in heart rate and blood pressure were greater in COREXIT EC9500A-exposed than in air-exposed rats at 1 d but not 7 d after the exposure. COREXIT EC9500A exposure also induced a rise in basal tone and reduced responsiveness of tail arteries to acetylcholine-induced vasodilation at 1 d but not 7 d following the exposure. These findings demonstrate that an acute exposure to COREXIT EC9500A exerts transient effects on cardiovascular and peripheral vascular functions.

Neurotoxicity Following Acute Inhalation Exposure to the Oil Dispersant COREXIT EC9500A

Consequent to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, there is an emergent concern about the short- and long-term adverse health effects of exposure to crude oil, weathered-oil products, and oil dispersants among the workforce employed to contain and clean up the spill. Oil dispersants typically comprise of a mixture of solvents and surfactants that break down floating oil to micrometer-sized droplets within the water column, thus preventing it from reaching the shorelines. As dispersants are generally sprayed from the air, workers are at risk for exposure primarily via inhalation. Such inhaled fractions might potentially permeate or translocate to the brain via olfactory or systemic circulation, producing central nervous system (CNS) abnormalities. To determine whether oil dispersants pose a neurological risk, male Sprague-Dawley rats were exposed by whole-body inhalation exposure to a model oil dispersant, COREXIT EC9500A (CE; approximately 27 mg/m3 × 5 h/d × 1 d), and various molecular indices of neural dysfunction were evaluated in discrete brain areas, at 1 or 7 d postexposure. Exposure to CE produced partial loss of olfactory marker protein in the olfactory bulb. CE also reduced tyrosine hydroxylase protein content in the striatum. Further, CE altered the levels of various synaptic and neuronal intermediate filament proteins in specific brain areas. Reactive astrogliosis, as evidenced by increased expression of glial fibrillary acidic protein, was observed in the hippocampus and frontal cortex following exposure to CE. Collectively, these findings are suggestive of disruptions in olfactory signal transduction, axonal function, and synaptic vesicle fusion, events that potentially result in an imbalance in neurotransmitter signaling. Whether such acute molecular aberrations might persist and produce chronic neurological deficits remains to be ascertained.

Pulmonary Effects after Acute Inhalation of Oil Dispersant (COREXIT EC9500A) in Rats

COREXIT EC9500A (COREXIT) was used to disperse crude oil during the 2010 Deepwater Horizon oil spill. While the environmental impact of COREXIT has been examined, the pulmonary effects are unknown. Investigations were undertaken to determine whether inhaled COREXIT elicits airway inflammation, alters pulmonary function or airway reactivity, or exerts pharmacological effects. Male rats were exposed to COREXIT (mean 27 mg/m3, 5 h). Bronchoalveolar lavage was performed on d 1 and 7 postexposure. Lactate dehydrogenase (LDH) and albumin were measured as indices of lung injury; macrophages, neutrophils, lymphocytes, and eosinophils were quantified to evaluate inflammation; and oxidant production by macrophages and neutrophils was measured. There were no significant effects of COREXIT on LDH, albumin, inflammatory cell levels or oxidant production at either time point. In conscious animals, neither breathing frequency nor specific airway resistance were altered at 1 hr, 1 d and 7 d postexposure. Airway resistance responses to methacholine (MCh) aerosol in anesthetized animals were unaffected at 1 and 7 d postexposure, while dynamic compliance responses were decreased after 1 d but not 7 d. In tracheal strips, in the presence or absence of MCh, low concentrations of COREXIT (0.001% v/v) elicited relaxation; contraction occurred at 0.003–0.1% v/v. In isolated, perfused trachea, intraluminally applied COREXIT produced similar effects but at higher concentrations. COREXIT inhibited neurogenic contractile responses of strips to electrical field stimulation. Our findings suggest that COREXIT inhalation did not initiate lung inflammation, but may transiently increase the difficulty of breathing.

Comparative toxicity of eight oil dispersants, Louisiana sweet crude oil (LSC), and chemically dispersed LSC to two aquatic test species

The present study describes the acute toxicity of eight commercial oil dispersants, South Louisiana sweet crude oil (LSC), and chemically dispersed LSC. The approach used consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the predominant dispersant applied during the DeepWater Horizon spill in the Gulf of Mexico. Static acute toxicity tests were performed using two Gulf of Mexico estuarine test species, the mysid shrimp (Americamysis bahia) and the inland silversides (Menidia beryllina). Dispersant-only test solutions were prepared with high-energy mixing, whereas water-accommodated fractions of LSC and chemically dispersed LSC were prepared with moderate energy followed by settling and testing of the aqueous phase. The median lethal concentration (LC50) values for the dispersant-only tests were calculated using nominal concentrations, whereas tests conducted with LSC alone and dispersed LSC were based on measured total petroleum hydrocarbon (TPH) concentrations. For all eight dispersants in both test species, the dispersants alone were less toxic (LC50s: 2.9 to >5,600 µl/L) than the dispersant-LSC mixtures (0.4-13 mg TPH/L). Louisiana sweet crude oil alone had generally similar toxicity to A. bahia (LC50: 2.7 mg TPH/L) and M. beryllina (LC50: 3.5 mg TPH/L) as the dispersant-LSC mixtures. The results of the present study indicate that Corexit 9500A had generally similar toxicity to other available dispersants when tested alone but was generally less toxic as a mixture with LSC.

Pulmonary effects of inhaled oil dispersant (COREXIT® EC9500A) in rats

COREXIT® EC9500A (CE) was used to disperse crude oil during the 2010 Deepwater Horizon oil spill response. While the environmental impact of CE has been examined, the pulmonary effects of CE are unknown. Here we investigated whether inhaled CE elicits airway inflammation, alters pulmonary function, or affects airway reactivity to methacholine (MCh). Rats were exposed to CE (mean 27 mg/m3, 5 h) and examined 1 and 7 d post‐exposure. Under anesthesia, the lung lavage fluid was harvested. Lactate dehydrogenase (LDH) and albumin (A) were measured as indices of lung injury, recovered lung cells were differentiated (macrophages, neutrophils, lymphocytes, and eosinophils) to evaluate inflammation, and oxidant production by macrophages was measured. There were no significant differences in LDH, A, inflammatory cell levels or oxidant production between air‐ and CE‐exposed groups at either time point. Pulmonary function assessed in conscious animals indicated that neither breathing frequency nor specific airway resistance were altered at 1 and 7 d post‐exposure. Airway resistance responses to MCh aerosol in anesthetized animals were unaffected at 1 and 7 d post‐exposure, while dynamic compliance responses were decreased at 1 d but not at 7 d post‐exposure. Our findings suggest that CE inhalation does not initiate lung inflammation, but may transiently increase the difficulty of breathing.

Mechanical responses to COREXIT® EC9500A in rat trachea in vitro

Oil dispersant COREXIT® EC9500A (CE) was used to reduce the environmental impact of the Deepwater Horizon oil spill in 2010. Little is known of the pulmonary effects of CE on airway smooth muscle and nerves. We investigated in vitro the effects of CE on rat tracheal preparations. In tracheal strips, CE (0.001 %v/v) elicited relaxation. Contraction occurred at higher concentrations (0.003–0.1 %v/v; EC50 0.0031 %v/v). CE (>0.1 %v/v) elicited relaxation of methacholine (MCh; 3×10−5 M)‐contracted strips (EC50 0.39 %v/v). CE (0.003 %v/v) had no effect on MCh‐induced tone but inhibited neurogenic contractile responses of strips to electrical field stimulation (10 Hz). In the isolated, perfused trachea preparation (IPT), in which agents may be applied separately to the mucosal or serosal surface, CE (0.3–10 %v/v) administered to the mucosal bath resulted in contraction. In MCh‐contracted perfused tracheas, mucosal CE (0.1–10 %v/v) elicited contraction followed by relaxation. Thus, CE was less potent in the IPT compared to strips. CE produced a progressive precipitate at >0.1 %v/v. Our results indicate that CE contracts airway smooth muscle and inhibits excitatory neurotransmission. Relaxation at high CE concentrations cannot be distinguished from precipitate formation or osmotic effects.

Tracking the Dispersant Applied during the MC252 Deepwater Horizon Incident

Abstract As part of the response strategy, dispersant was applied to oil from the MC252 Deepwater Horizon both at the surface and at the well head. Around 90% of the dispersant used was Corexit EC9500A, with a small amount of Corexit 9527 used during the initial stages of the response. In total, around 1.8 million gallons of dispersants were applied. The purpose of the dispersant was as follows: Remove oil from the surface and enhance its microbial degradation within the water column Reduce airborne concentrations of volatile organic compounds (VOCs) around the source site Reduce the amounts of oil ultimately reaching the shoreline. Corexit EC9500A contains several surface active agents in a solvent package; all of the components are individually used in other formulations in cosmetics, medicines, or cleaning products. This report focuses on one of these, dipropylene glycol n-butyl ether (DPnB), a component of the solvent package with weak surfactant properties itself. Corexit EC9500A contains two isomers...

Wave Tank and Swirling Flask Dispersant Effectiveness Testing on Fresh Mississippi Canyon 252 Oil

Nine dispersants were tested at the high energy setting (Figure 2). Five dispersants that performed well at high energy were then tested at the low energy setting (Figure 3).Each test case was completed in triplicate. Four of the dispersants tested did not perform any better than the control tests (see Figure 2). Three dispersants (Corexit 9500a, Corexit 9527a and Finasol OSR 52) clearly performed better than all of the others. These dispersants generated smaller oil-drop sized dispersions in the form of classic cafe-au-lait clouds. The Dispersit SPC 1000 and JD-2000 dispersants also worked well at the high-energy setting but neither of these dispersants generated small drop sized cafe-au-lait clouds of dispersed oil. High Energy SL Ross Wave Tank Test Results

Comparative Acute Toxicity of Eight Oil Spill Dispersants, Louisiana Crude Oil and Chemically Dispersed Oil to Two Gulf of Mexico Aquatic Species

Abstract Approximately two million gallons of oil dispersants were applied in response to the Deepwater Horizon spill. This study determined the acute toxicity of eight commercial oil dispersants, South Louisiana crude oil (SLC), and chemically dispersed SLC using each of the eight oil dispersants. The approach utilized consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the dispersant applied offshore to surface waters and directly to the leak source. Static acute toxicity tests were performed with two Gulf of Mexico estuarine test species to determine 48-hr LC50 values for mysid shrimp (Americamysis bahia) and 96-hr LC50 values for inland silversides (Menidia berylina). Dispersant-only test solutions were prepared with high energy mixing, whereas water accommodated fractions of SLC and chemically dispersed SLC were prepared with moderate energy followed by settling and testing of the aqueous phase. For all e...