Deepwater Horizon Research Articles

Using Blood Gas Analysis and Capnography to Determine Oxygenation Status in Bottlenose Dolphins (Tursiops truncatus) Following the Deepwater Horizon Oil Spill.

Following the Deepwater Horizon (DWH) oil spill in 2010, poor pulmonary health and reproductive failure in bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico were well-documented. One postulated etiology for the increased fetal distress syndrome and pneumonia found in affected perinatal dolphins was maternal hypoxia caused by lung disease. The objective of this study was to evaluate the utility of blood gas analysis and capnography in determining oxygenation status in bottlenose dolphins with and without pulmonary disease. Blood and breath samples were collected from 59 free-ranging dolphins in Barataria Bay, Louisiana (BB), during a capture-release health assessment program, and from 30 managed dolphins from the U.S. Navy Marine Mammal Program in San Diego, CA. The former was the oil-exposed cohort and the latter served as a control cohort with known health histories. Capnography and select blood gas parameters were compared based on the following factors: cohort, sex, age/length class, reproductive status, and severity of pulmonary disease. Animals with moderate-severe lung disease had higher bicarbonate concentrations (p = 0.005), pH (p < 0.001), TCO2 (p = 0.012), and more positive base excess (p = 0.001) than animals with normal-mild disease. Capnography (ETCO2) was found to have a weak positive correlation with blood PCO2 (p = 0.020), with a mean difference of 5.02 mmHg (p < 0.001). Based on these findings, indirect oxygenation measures, including TCO2, bicarbonate, and pH, show promise in establishing the oxygenation status in dolphins with and without pulmonary disease.

Volatile Hydrocarbon Exposures and Incident Coronary Heart Disease Events: Up to Ten Years of Follow-up among Deepwater Horizon Oil Spill Workers.

During the 2010 Deepwater Horizon (DWH) disaster, response and cleanup workers were potentially exposed to toxic volatile components of crude oil. However, to our knowledge, no study has examined exposure to individual oil spill-related chemicals in relation to cardiovascular outcomes among oil spill workers. Our aim was to investigate the association of several spill-related chemicals [benzene, toluene, ethylbenzene, xylene, n-hexane (BTEX-H)] and total hydrocarbons (THC) with incident coronary heart disease (CHD) events among workers enrolled in a prospective cohort. Cumulative exposures to THC and BTEX-H across the cleanup period were estimated via a job-exposure matrix that linked air measurement data with self-reported DWH spill work histories. We ascertained CHD events following each worker's last day of cleanup work as the first self-reported physician-diagnosed myocardial infarction (MI) or a fatal CHD event. We estimated hazard ratios (HR) and 95% confidence intervals for the associations of exposure quintiles (Q) with risk of CHD. We applied inverse probability weights to account for bias due to confounding and loss to follow-up. We used quantile g-computation to assess the joint effect of the BTEX-H mixture. Among 22,655 workers with no previous MI diagnoses, 509 experienced an incident CHD event through December 2019. Workers in higher quintiles of each exposure agent had increased CHD risks in comparison with the referent group (Q1) of that agent, with the strongest associations observed in Q5 (range of ). However, most associations were nonsignificant, and there was no evidence of exposure-response trends. We observed stronger associations among ever smokers, workers with education, and workers with body mass index . No apparent positive association was observed for the BTEX-H mixture. Higher exposures to volatile components of crude oil were associated with modest increases in risk of CHD among oil spill workers, although we did not observe exposure-response trends. https://doi.org/10.1289/EHP11859.

Aerial remote sensing of sub-sea dispersant injection effects during the Deepwater Horizon (MC-252) oil spill

During the Deepwater Horizon oil spill in 2010, subsea dispersant injection (SSDI) was utilized for the first time in an effort to reduce the amount of oil reaching the sea surface and thus potentially decrease its environmental impact and enhance responders' safety. Since then, controversy has developed about SSDI's effectiveness. Most of the analysis is based on modeling, with some models concluding SSDI significantly reduced surfacing oil volumes, and others predicting that processes unrelated to the dispersant caused most of the subsurface oil retention. This study utilized a multispectral aerial sensor image time series to correlate the surface area covered by freshly upwelled oil with changes in SSDI rates, accounting for an approximate 4 hour oil rise time lag. A significant negative correlation was found between oil-covered surface area and SSDI rates, providing direct observation support that the technique did reduce the amount of surfacing oil around the wellhead.

Environmental awareness and shareholder proposals: the case of the Deepwater Horizon oil spill disaster

Purpose The authors study the effect of increasing environmental awareness on shareholders' activism. Specificallly, this study aims to examine whether growing environmental awareness is reflected in more aggressive environmental shareholder proposals. Design/methodology/approach This study uses the 2010 Deepwater Horizon oil spill disaster as an exogenous event that increased shareholders' environmental awareness. This study analyzes the spill’s effect on the tone of proposals about environmental issues and nonenvironmental topics. Findings After the disaster, the tone of environmental proposals (i.e. the treatment group) is significantly more negative. In contrast, the tone of nonenvironmental proposals (i.e. the control group) is unaffected. This study interprets this finding as direct evidence that the oil spill led to increased shareholder environmental activism through proposals that targeted the environmental risks surrounding the business more aggressively. By contrast, this study finds no effect of the oil spill on the tone of managers' responses to the proposals, consistent with managers refraining from emphasizing environmental threats. Originality/value Anecdotal evidence and recent studies suggest a link between environmental disasters and shareholder pressure for corporate change. However, no prior research has investigated the channel through which shareholders could have exerted such pressure or has looked for direct evidence of it in the negotiations between shareholders and managers. By finding such evidence in shareholder proposals, this study fills in this gap.

Sun may make oil stick atop cold ocean

New research suggests that oil spills in cold locations with lots of sun exposure could play out much differently than warm-water spills, such as the one that followed the Deepwater Horizon explosion in 2010. Last week at the ACS Spring 2023 meeting, Danielle Haas Freeman , a PhD candidate at Woods Hole Oceanographic Institution, detailed how sunlight-driven photooxidation could leave a larger-than-expected fraction of spilled oil suspended on the surface of cold water. “What that means is that you would have more oil to clean up, and then you’d also end up with potentially more oil reaching sensitive coastal ecosystems,” said Collin P. Ward , a geochemist at Woods Hole who led the study. Freeman and Ward looked at the physical properties governing two different pathways for oil to be removed naturally from the water’s surface: entrainment, a process in which oil gets broken up and drawn down into the

Framing Environmental Disasters for Nonviolent Protest: A Content Analysis

ABSTRACT This article presents a content analysis of news coverage of three environmental disasters: the 2014 Mount Polley mine leak, the 2010 Deepwater Horizon oil spill, and the 2011 Fukushima nuclear disaster. The aim is to better understand how political actors talk about industrial environmental disasters in their aftermath. Since most people understand dramatic events through news media, an examination of post-disaster media framing may begin to shed light on the variation of public response after disasters. Specifically, the findings challenge some prevailing assumptions about nonviolent protest mobilization and prompt a further investigation of the role of uncertainty in political participation.

Shifting linguistic patterns in oyster restoration news articles surrounding the Deepwater Horizon disaster

Populations of the eastern oyster Crassostrea virginica are declining globally. With the loss of oysters, sustainable provision of natural resources and ecosystem services are also threatened. In 2010, the Deepwater Horizon (DWH) oil spill became the largest marine oil spill in history, imperiling coastal and marine habitats in the Gulf of Mexico. Whereas ecological restoration serves as an important tool in natural resource management, its success depends on achieving ecological objectives and meeting public expectations. However, little is known about how the public perceives ecological restoration—even less in the context of disasters. It has long been understood that mass media messaging helps shape public understanding. Documenting patterned representation of oyster restoration in mass media texts can help set goals, improve stakeholder communication, and ensure required support for restoration activities. To address this goal, this study asks, does newspaper language on the topic of oyster reef restoration change in relation to an environmental disaster? If so, how? A 1.1 million-word Deepwater Horizon Oyster Restoration (DHORN) Corpus—a comprehensive body of newspaper articles about oyster restoration from 3 national and 18 gulf-state newspapers—was developed for the period April 2008–April 2014. The distribution and deployment of collocates of oyster* across three DHORN subcorpora delimited by time (pre-, during, and post-Deepwater Horizon oil spill) were compared through iterative quantitative and qualitative analysis. Examination of salient collocates in use over time indicated an increase in the representation of oysters as quantifiable entities during/post-DWH; at the same time, there was a decrease in the representation of the roles of oyster* in the Gulf ecosystem. Furthermore, multiple propositions associating oysters and oyster restoration activity with DWH and oil spills were introduced into language use by the disaster and persisted for years afterwards. This association was not present pre-DWH. Understanding shifts in linguistic patterns of oyster restoration in news articles before, during, and after Deepwater Horizon can be used to deliberately refine communication between the conservation community and both journalists and policymakers to promote conservation initiatives.

Spatiotemporal patterns in the prevalence of microscopic hepatic changes in Gulf of Mexico Tilefish (Lopholatilus chamaeleonticeps) and associations with hepatic PAHs

Following the 2010 Deepwater Horizon blowout, demersal longline surveys were conducted across the Gulf of Mexico (GoM) continental shelf to evaluate polycyclic aromatic hydrocarbon (PAH) exposure, tissue accumulation, and health indices in demersal fishes. Tilefish (Lopholatilus chamaeleonticeps), a target species due to Gulf-wide distribution with documented high exposure to PAHs, were collected in the north central GoM at repeat stations 2012 to 2015, and from the northwest GoM, Bay of Campeche, and Yucatán Shelf in 2015 and 2016. Liver samples (n = 239) were analyzed for microscopic hepatic changes (MHCs) by a board-certified veterinary pathologist. Histological analyzes identified 14 MHCs. Prevalence of MHCs was generally uniform throughout the GoM, except for low prevalence on the Yucatán Shelf. Inflammatory and vacuolar changes were most prevalent, while pre-neoplasia and neoplasia were rare. Tilefish sampled annually in the north central GoM showed increases in inflammatory MHCs and glycogen-type vacuolar change over time, while lipid-type vacuolar change decreased over time. Short-term exposure to PAHs was assessed by measuring PAH metabolites in bile (n = 100) using high performance liquid chromatography with fluorescence detection. Longer-term accumulation of PAHs in tissue was assessed by analyzing liver (n = 111) for PAHs and alkylated homologs using QuEChERS extractions and gas chromatography tandem mass spectrometry. Six MHCs including glycogen-type vacuolar change, biliary fibrosis, foci of cellular alteration, parasites, hepatocellular atrophy, and necrosis were significantly associated with hepatic PAH accumulation in Tilefish from the northern central GoM; however, no MHCs were associated with biliary PAH metabolites. Combined with previous studies of PAH exposure and health indices in north central GoM Tilefish post-Deepwater Horizon, which also identified decreases in hepatic lipid storage and Fulton's condition factor that were correlated to increasing PAH exposure, these data indicate concerning temporal trends and changes in hepatic energy storage.

Are environmental lawsuits related to the cost of bank loans?

PurposeConsidering the importance of environmental lawsuits in the capital market specifically and society more generally, the authors examine whether environmental lawsuits are related to the cost of bank loans for the first time.Design/methodology/approachThis study uses a US sample of 7,684 loans from 1,409 individual borrowing firms over the 1995–2015 period. The hypothesis is tested using lagged data from the year before the start of a bank loan, and firm fixed effects panel regression analysis is applied to control for correlated omitted variable bias. To further address endogeneity concerns, the authors use a difference in differences analysis that exploits the Deepwater Horizon oil spill on April 20, 2010, to establish causality. Finally, the authors use the entropy balancing method as an additional endogeneity check.FindingsThe authors find a positive relationship between environmental lawsuits and firms' bank loan costs. The results are economically significant. In particular, a one standard deviation increase in environmental lawsuits is related to a 2.07 basis point increase in bank loan costs. The results are robust to various endogeneity checks. Cross-sectional analyses indicate that a poor information environment, weak corporate governance, and low corporate social responsibility (CSR) levels strengthen the positive relationship between environmental lawsuits and bank loan costs. Finally, additional analyses show that environmental lawsuits are significantly negatively related to the loan amount and maturity contract provisions.Originality/valueThe authors provide new empirical evidence that increasing understanding of the economic consequences of environmental lawsuits on bank loan costs.

Metabarcoding analysis of meiobenthic biodiversity along the Gulf of Mexico continental shelf

This study explores how diverse the meiobenthic (meiofauna and other benthic micro-eukaryotes) community is throughout the United States Gulf of Mexico (GOM) continental shelf. In late 2010 and 2011, 51 sediment samples were collected along GOM from Texas through Florida at a range of depths (40m–496m). An additional six deep-sea slope sediment cores were collected in December 2010 near the Deepwater Horizon platform (1370–1385m and 1865m). Metabarcoding of the 18S hypervariable V9 region was conducted to assess biodiversity. Within continental shelf samples, there was greater meiobenthic diversity off the Eastern GOM coast in comparison to both Central and Western GOM coast locations. The Eastern GOM coast has known sediment differences from Western GOM sites. These sediment differences along with influences from the Gulf of Mexico Loop Current may account for observed variations in GOM meiobenthic diversity.

Legal Protection of the Marine Environment from Oil and Petroleum Product Spills

The article deals with social relations arising in the process of preventing and eliminating emergency oil and petroleum product spills in the marine environment. The danger of pollution of the marine environment by oil and petroleum products is reviewed, two major accidents related to the spill of oil and petroleum products are mentioned: the release of oil from the Exxon Valdez tanker and the Deepwater Horizon oil spill. The methods used to eliminate accidents in the Baltic Sea, as well as some features of this region, are considered. The special role of the Polar Code in the prevention of pollution of polar waters by oil and petroleum products is considered. The article also discusses the requirements for the prevention of accidental spills contained in international acts. The article notes that most of the existing international legal norms, as well as legal acts of national legislation, are aimed at ensuring compliance with the established rules for the transportation of oil and petroleum products, requirements for the operation of ships, their design features, as well as for the proper operation of equipment. It is necessary to eliminate gaps in legislation regarding the regulation of oil collection under ice in the polar region. It seems necessary to legislatively regulate the use of special means for monitoring oil spills. Legislation in the field of forecasting, accident prevention, as well as taking into account the natural features of the region of production and transportation of petroleum products needs further improvement

Exploring the use of Transition Path Theory in building an oil spill prediction scheme

The Transition Path Theory (TPT) of complex systems has proven to be a robust means to statistically characterize the ensemble of trajectories that connect any two preset flow regions, say 𝒜 and ℬ, directly. More specifically, transition paths are such that they start in 𝒜 and then go to ℬ without detouring back to 𝒜 or ℬ. This way, they make an effective contribution to the transport from 𝒜 to ℬ. Here, we explore its use for building a scheme that enables predicting the evolution of an oil spill in the ocean. This involves appropriately adapting TPT such that it includes a reservoir that pumps oil into a typically open domain. Additionally, we lift up the restriction of the oil not to return to the spill site en route to a region that is targeted to be protected. TPT is applied on oil trajectories available up to the present, e.g., as integrated using velocities produced by a data assimilative system or as inferred from high-frequency radars, to make a prediction of transition oil paths beyond, without relying on forecasted oil trajectories. As a proof of concept, we consider a hypothetical oil spill in the Trion oil field, under development within the Perdido Foldbelt in the northwestern Gulf of Mexico, and the Deepwater Horizon oil spill. This is done using trajectories integrated from climatological and hindcast surface velocity and winds as well as produced by satellite-tracked surface drifting buoys, in each case discretized into a Markov chain that provides a framework for the TPT-based prediction.

A multi-targeted investigation of Deepwater Horizon crude oil exposure impacts on the marine teleost stress axis

The toxicity of the polycyclic aromatic hydrocarbons (PAHs) in Deepwater Horizon (DWH) oil is well-established, but a knowledge gap exists regarding how this combination of PAHs affects the vertebrate stress axis. We hypothesized that (1) marine vertebrates exposed to DWH PAHs experience stress axis impairment, and co-exposure to an additional chronic stressor may exacerbate these effects, (2) serotonin (5-hydroxytryptamine; 5-HT) may act as a secondary cortisol secretagogue in DWH PAH-exposed fish to compensate for impairment, and (3) the mechanism of stress axis impairment may involve downregulation of cyclic adenosine monophosphate (cAMP; as proxy for melanocortin 2 receptor (MC2R) functionality), total cholesterol, and/or mRNA expression of CYP1A and steroidogenic proteins StAR, P450scc, and 11β-h at the level of the kidney. We found that in vivo plasma cortisol and plasma adrenocorticotropic hormone (ACTH) concentrations in Gulf toadfish exposed to an environmentally relevant DWH PAH concentration (ΣPAH50= 4.6 ± 1.6 μg/L) for 7 days were not significantly different from controls, whether fish were chronically stressed or not. However, the rate of cortisol secretion by isolated kidneys after acute stimulation with ACTH was significantly lower in PAH-exposed toadfish compared to clean seawater (SW) controls. 5-HT does not appear to be acting as a secondary cortisol secretagogue, rather, PAH-exposed + stressed toadfish exhibited significantly lower plasma 5-HT concentrations than clean SW + stressed fish as well as a reduced sensitivity to 5-HT at the level of the kidney. There was a tendency for kidney cAMP concentrations to be lower in PAH-exposed fish (p = 0.069); however, mRNA expression of steroidogenic proteins between control and PAH-exposed toadfish were not significantly different and a significant elevation in total cholesterol concentration in PAH-exposed toadfish compared to controls was measured. Future work is needed to establish whether the slower cortisol secretion rate by isolated kidneys of PAH-exposed fish is detrimental, to determine the potential role of other secretagogues in compensating for the impaired kidney interrenal cell function, and to determine whether there is a reduction in MC2R mRNA expression or an impairment in the function of steroidogenic proteins.

Temporal variability of microbial response to crude oil exposure in the northern Gulf of Mexico

Oil spills are common occurrences in the United States and can result in extensive ecological damage. The 2010 Deepwater Horizon oil spill in the Gulf of Mexico was the largest accidental spill recorded. Many studies were performed in deep water habitats to understand the microbial response to the released crude oil. However, much less is known about how planktonic coastal communities respond to oil spills and whether that response might vary over the course of the year. Understanding this temporal variability would lend additional insight into how coastal Florida habitats may have responded to the Deepwater Horizon oil spill. To assess this, the temporal response of planktonic coastal microbial communities to acute crude oil exposure was examined from September 2015 to September 2016 using seawater samples collected from Pensacola Beach, Florida, at 2-week intervals. A standard oil exposure protocol was performed using water accommodated fractions made from MC252 surrogate oil under photo-oxidizing conditions. Dose response curves for bacterial production and primary production were constructed from 3H-leucine incorporation and 14C-bicarbonate fixation, respectively. To assess drivers of temporal patterns in inhibition, a suite of biological and environmental parameters was measured including bacterial counts, chlorophyll a, temperature, salinity, and nutrients. Additionally, 16S rRNA sequencing was performed on unamended seawater to determine if temporal variation in the in situ bacterial community contributed to differences in inhibition. We observed that there is temporal variation in the inhibition of primary and bacterial production due to acute crude oil exposure. We also identified significant relationships of inhibition with environmental and biological parameters that quantitatively demonstrated that exposure to water-soluble crude oil constituents was most detrimental to planktonic microbial communities when temperature was high, when there were low inputs of total Kjeldahl nitrogen, and when there was low bacterial diversity or low phytoplankton biomass.

Automatic detection of thin oil films on water surfaces in ultraviolet imagery

AbstractAmong the various remote sensing technologies that have been applied to monitor oil spills on the sea surface, passive ultraviolet (UV) imaging is a controversial one that has raised some disputes in the community of oil spill remote sensing. As a result, the research and applications of oil spill detection using passive UV imaging have not been as developed as other methods. In order to clarify some existing questions on oil spill detection using passive UV remote sensing technology, this paper discusses the needs of thin oil film detection, examines the feasibility of thin oil film detection using passive UV imaging through field experiments under controlled conditions and validates it with the UV imagery derived from the airborne visible/infrared imaging spectrometer (AVIRIS) observation of the Deepwater Horizon oil spill. Two types of fully automatic models are designed to extract the thin oil films on the water surface: (1) a binary classification model based on an adaptive threshold; (2) an unsupervised image segmentation model based on image clustering and greyscale histogram analysis. The two models are tested on the UV imagery obtained through both field experiments and AVIRIS observations. The results indicate that the binary classification model can extract the thin oil films with reasonable accuracy under stable imaging conditions, while the unsupervised image clustering model can robustly detect the thin oil films at the cost of higher computational complexity. These results infer that passive UV imaging is an effective way to detect thin oil films and could be applied to provide early warning at the beginning stage of oil spills and reduce further damage. It may also be applied as a supplementary method for oil spill detection to achieve comprehensive oil spill monitoring.

Ocean oil spill detection from SAR images based on multi-channel deep learning semantic segmentation

One of the major threats to marine ecosystems is pollution, particularly, that associated with the offshore oil and gas industry. Oil spills occur in the world's oceans every day, either as large-scale spews from drilling-rig or tanker accidents, or as smaller discharges from all sorts of sea-going vessels. In order to contribute to the timely detection and monitoring of oil spills over the oceans, we propose a new Multi-channel Deep Neural Network (M-DNN) segmentation model and a new and effective Synthetic Aperture Radar (SAR) image dataset, that enable us to emit forewarnings in a prompt and reliable manner. Our proposed M-DNN is a pixel-level segmentation model intended to improve previous DNN oil-spill detection models, by taking into account multiple input channels, complex oil shapes at different scales (dimensions) and evolution in time, and look-alikes from low wind speed conditions. Our methodology consists of the following components: 1) New Multi-channel SAR Image Database Development; 2) Multi-Channel DNN Model based on U-net and ResNet; and 3) Multi-channel DNN Training and Transfer Learning. Due to the lack of public oil spill databases guaranteeing a correct learning process of the M-DNN, we developed our own database consisting of 16 ENVISAT-ASAR images acquired over the Gulf of Mexico during the Deepwater Horizon (DWH) blowout, off the west coast of South Korea during the Hebei Spirit oil tanker collision, and over the Black Sea. These images were pre-processed to create a 3-channel input image IM = {IO, IW, IV}, to feed in and train our M-DNN. The first channel IO represents the radiometric values of the original SAR Images, the second and third channels are derived from IO; in particular, IW represents the output of the wind speed estimation using CMOD5 algorithm (Hersbach et al., 2003) and IV represents the variance of IO that incorporates texture information and at the same time encapsulates oil spill transition regions. IM channels were split and linearly transformed for data augmentation (rotation and reflection) to obtain a total of 80,772 sub-images of 224 × 224 pixels. From the entire database, 80 % of the sub-images were used in the DNN training process, the remaining (20 %) was used for testing our final architecture. Our experimental results show higher pixel-level classification accuracy when 2 or 3 channels are used in the M-DNN, reaching an accuracy of 98.56 % (the highest score reported in the literature for DNN models). Additionally, our M-DNN model provides fast training convergence rate (about 14 times better on the average than previous works), which proves the effectiveness of our proposed method. According to our knowledge, our work is the first multi-channel DNN based scheme for the classification of oil spills at different scales.

In Memoriam: William T. Hogarth

In Memoriam: William T. Hogarth

The long-run relationship between the prices of WTI and Brent crude oils – Periodogram based cointegration analyses

The purpose of this article is to investigate the presence of a cointegrating relationship between the prices of the two most important crude oil price benchmarks, which are West Texas Intermediate and Brent, for June 1987-July 2021. We use the periodogram-based methodology. Our finding suggests a global long-run relationship between two major crude oil prices for the 1987:06-2010:03 period until the Deepwater Horizon oil spill took place at the Macondo Field, located in the Gulf of Mexico. After this accident, the relationship breaks down. We also find statistically significant closely 12-month common periodicities in both series for the pre-oil spill accident. We conclude that the cointegrating relationship between the two oil prices maintained up to 2010:03. This finding provides a practical implication that these two crude oil prices cannot be used for hedging purposes after this date.

Risk of longer-term neurological conditions in the Deepwater Horizon Oil Spill Coast Guard Cohort Study – Five years of follow-up

BackgroundLong-term neurological health risks associated with oil spill cleanup exposures are largely unknown. We aimed to investigate risks of longer-term neurological conditions among U.S. Coast Guard (USCG) responders to the 2010 Deepwater Horizon (DWH) oil spill.MethodsWe used data from active duty members of the DWH Oil Spill Coast Guard Cohort Study (N=45224). Self-reported oil spill exposures were ascertained from post-deployment surveys. Incident neurological outcomes were classified using International Classification of Diseases, 9th Revision, codes from military health encounter records up to 5.5 years post-DWH. We used Cox Proportional Hazards regression to calculate adjusted hazard ratios (aHR) and 95% confidence intervals (CI) for various incident neurological diagnoses (2010–2015). Oil spill responder (n=5964) vs. non-responder (n= 39260) comparisons were adjusted for age, sex, and race, while within-responder comparisons were additionally adjusted for smoking.ResultsCompared to those not responding to the spill, spill responders had reduced risks for headache (aHR=0.84, 95% CI: 0.74-0.96), syncope and collapse (aHR=0.74, 95% CI: 0.56-0.97), and disturbance of skin sensation (aHR=0.81, 95% CI: 0.68-0.96). Responders reporting ever (n=1068) vs. never (n=2424) crude oil inhalation exposure were at increased risk for several individual and grouped outcomes related to headaches and migraines (aHR range: 1.39-1.83). Crude oil inhalation exposure was also associated with elevated risks for an inflammatory nerve condition, mononeuritis of upper limb and mononeuritis multiplex (aHR=1.71, 95% CI: 1.04-2.83), and tinnitus (aHR=1.91, 95% CI: 1.23-2.96), a condition defined by ringing in one or both ears. Risk estimates for those neurological conditions were higher in magnitude among responders reporting exposure to both crude oil and oil dispersants than among those reporting crude oil only.ConclusionIn this large study of active duty USCG responders to the DWH disaster, self-reported spill cleanup exposures were associated with elevated risks for longer-term neurological conditions.

Disturbance legacies and shifting trajectories: Marsh soil strength and shoreline erosion a decade after the Deepwater Horizon oil spill

Marsh resilience post disturbance is strongly dependent on the belowground dynamics affecting the emergent plants aboveground. We investigated the long-term impacts at the marsh-water interface in coastal wetlands of south Louisiana after the 2010 Deepwater Horizon oil spill with a combination of fieldwork (2010–2018) and spatial analysis (1998–2021). Data were collected on shoreline erosion rates, marsh platform elevation heights and cantilever overhang widths, and soil strength up to 1 m depth. Oil concentration in the top 5 cm of the marsh soil were determined using gas chromatography/mass spectrometry and were 1000 times higher than before the spill and remained 10 times higher eight years post-oiling. The oiling initially caused the marsh edge to subside, and chronic effects lowered soil strength, creating a faster erosion rate and deeper water within 150 cm of the shoreline. Soil strength declined by 50% throughout the 1 m soil profile after oiling and has not recovered. The mean erosion rate for 11 years post-spill was double that before oiling and there was an additive impact on erosion rates after Hurricane Isaac. Erosion appeared to have recovered to pre-spill rates by 2019, however from 2019 to 2021, the rate increased by 118% above the pre-spill rate. The continuing loss of soil strength indicates that the belowground biomass was seriously compromised by oiling. The perpetuation of oil in the remaining marsh may have set a new baseline for soil strength and subsequent storm induced erosional events. The remaining marsh soils retain chronic physical and biological legacies compromising recovery for more than a decade that may be evident in other marsh habitats subject to oiling and other stressors.