Gulf Longitudinal Follow-up (GuLF) Study

National Institute Of Environmental Health Sciences

Investigators

Linked publications, trials & patents

Abstract

The Gulf Long-term Follow-up Study (GuLF STUDY, https://gulfstudy.nih.gov/en/index.html) was initiated in response to the April 2010 explosion of the Deepwater Horizon (DWH) drilling rig and resulting oil spill in the Gulf of Mexico, the largest marine oil spill in U.S. history. A total of 32,608 oil spill response and clean-up workers and non-workers completed an enrollment questionnaire (2011-2013). Over 11,000 individuals from the Gulf states completed a home visit that included collection of biospecimens and anthropometric measurements, including pulmonary function measures. In response to community concerns about reports of oil-related chemicals in the blood of some people years after the spill, we analyzed samples from 1,000 participants collected at home visit for volatile organic compounds including BTEX-h and styrene as well as metals. Levels of these chemicals, apart from styrene, a chemical unrelated to the oil spill, were not different from those in a nationally representative and local sample of NHANES participants once cigarette smoking was considered. Follow-up data were collected from 21,256 participants between 2013-2016. Mental health trajectories were assessed among those who had symptoms of depression, PTSD, or anxiety at enrollment and a random sample of the remainder in four mental health interviews over two years (n=2,969). Participants (n=3,403) living within 60 miles of New Orleans, LA or Mobile, AL completed a clinical exam (2014-2016) that included additional lung function tests, assessment of neurological function, and biological sample collection. A second follow-up interview was completed in May 2021 with a response rate of 61% among those who completed the first follow-up. Participants are being followed via linkage to cancer registries and the National Death Index. This year we received complete data for the National Death Index through 2022. Investigators completed the Data User Agreement for the Virtual Pool Registry-Cancer Linkage System and are in the process of pursuing Phase II linkages with 30 cancer registries. We are focusing on completing linkages with VPR states where we had >30 GuLF participants. To date we have received data back from 11 registries. Extensive efforts were made to characterize the oil exposures of study participants. We used questionnaire and measurement data taken during the spill to develop job exposure matrices for a wide range of possible exposures. This work involved recalibrating exposure measurements taken during cleanup, identifying numerous distinct exposure groups performing like-tasks defined by timing of work relative to the capping of the well, activities, and location, and developing new statistical approaches to deal with values below the LOD and other censoring. Ordinal exposure metrics (for THC, hierarchical job class, and exposure to burning and dispersants) have now been supplemented with quantitative measures of specific oil spill chemicals including BTEX-H chemicals. A measure of dermal hydrocarbon exposure was recently finalized and is now incorporated into analyses (Chen et al., 2025). Two dermal exposure measures representing mixtures of volatile organic compounds (VOCs) and a mixture of non-VOC oil related chemicals were linked to participant data were incorporated into analyses completed this year. This year, in an effort to expand assessment of subclinical changes related to oil spill exposures and other environmental factors, Dr. Sandler’s group analyzed peripheral blood-based proteomic profiles comprising 11,000 proteins measured via the SomaLogic SomaScan Assay among 1,215 participants selected from the pool of a subsample of 1392 males previously selected for genome- and epigenome-wide studies and evaluation of biomarkers of liver, kidney, and metabolic function to maximize biomarker overlap. Participants were also selected to have a range of environmental and sociodemographic characteristics. Planned analyses in the next year include assessment of proteomic signatures related to natural hazards and neighborhood deprivation. We will also explore OSRC work related exposures in relation to protein patterns in peripheral blood. Research Update This year, Dr. Sandler’s group continued to focus research efforts on studying health effects of oil spill cleanup work exposures in the GuLF Study population. Primary health outcomes of interest included skin conditions, neurological function, and cardiovascular disease-related risk factors including hypertension and diabetes. Other environmental factors were also explored for their potential impacts on the health of the GuLF Study cohort including natural hazard risks and ambient air pollution. Skin conditions Whereas many studies have investigated health effects of inhalation exposure among OSRC workers, yet skin complaints were among the most frequently reported by oil spill workers and others who engaged in water-based activities in the Gulf region. New work this year focused on incorporated OSRC-work dermal exposure estimates created for the study (‘GuLF Dream’ Model, described in Gorman Ng et al., 2019 and Stewart et al., 2022). To this end, Dr. Sandler’s group evaluated a variety of self-reported skin conditions and incident eczema in association with chemical skin contact. Exposures examined included overall duration of work, jobs performed, and skin contact with crude oil/tar, dispersants, and decontamination chemicals. Cumulative dermal exposure to polycyclic aromatic hydrocarbons (PAHs) from oil/tar was estimated based on the “GuLF DREAM model”. Findings showed that duration of OSRC work was positively associated with skin conditions and eczema diagnoses, and that workers in operations, response, and decontamination jobs had higher skin condition prevalence (during cleanup: PR range=3.13–4.51; at enrollment: PR range=2.20–2.94) and eczema risk (RR range=1.44–1.89) compared to support workers. After adjusting for co-exposures, associations of prevalent skin conditions during cleanup with dermal exposure to oil/tar, decontamination work, dispersants, and PAHs remained apparent, whereas eczema diagnosis was associated with exposure to both oil/tar and PAHs. Effect estimates were on average 21 % lower among workers who used rubber/synthetic gloves suggesting a modifying role of personal protective equipment use. Diabetes Research published this year (Jardel et al., 2025, Environ. Res) evaluated diabetes incidence associated with respiratory BTEX-H exposures individually and as a mixture and explored potential for effect measure modification by several sociodemographic factors. Exposure to the BTEX-H chemicals was associated with diabetes, with elevated hazard ratios for third and fourth quartiles of exposure compared to the first quartile. For example, total BTEX-H, Q3 and Q4 HRs were 1.10 95 %CI (0.91, 1.33) and 1.27 95 %CI (1.05, 1.53), respectively. The HR associated with a three-quartile increase in the BTEX-H mixture was 1.31 95 %CI (1.07, 1.59). Stratified analyses showed little variation by race, though risk estimates were most apparent among White participants. There was evidence of effect modification by a measure of neighborhood disadvantage (the Area Deprivation Index). In related work that is in-press, associations between oil spill chemicals and changes in HbA1c levels were less clear. Hypertension This year, the Sandler group also examined for the first time OSRC-work related individual and total BTEX-H exposures (ppb-days) in relation to hypertension prevalence and systolic and diastolic blood pressure measures (Patel et al., 2025, Sci Tot Env). Mixture models (quantile g-computation) were used to additionally examine any effects related to the BTEX-H mixture. Findings from this study showed individual BTEX-H components were modestly associated with hypertension prevalence and systolic and diastolic BP. Strongest associations with hypertension were observed in quartile 4 versus quartile 1 of most exposures (range of PRs: 1.06-1.15). The BTEX-H mixture was associated with small elevations in systolic (β = 0.60 mmHg, 95% CI: 0.26, 0.94) and diastolic (β = 0.49 mmHg, 95% CI: 0.24, 0.73) BP. A related paper (in press) examining the incidence of hypertension in the years following the disaster shows that exposure to the oil spill chemical mixture as well as individual chemicals is associated with self-reported incident hypertension. Neurological health outcomes The Sandler group continued to assess impacts of OSRC work exposures on neurological function. Norris et al. evaluated fine particulate matter from burning oil and gas in relation to neurological symptoms among the cleanup workers (Norris et al., 2025, Environ Sci Proc & Imp). Among 9,914 OSRC workers who worked on the water, analyses examined aggregate outcomes (central nervous system [CNS; dizziness, sweating, palpitations, nausea, or migraine/severe headache] and peripheral nervous system [PNS; tingling/numbness in extremities, blurred vision, or stumbling] symptoms) and individual symptoms (CNS and PNS symptoms, plus insomnia, vomiting, seizures, and fatigue). PM2.5 concentrations were estimated via Gaussian plume dispersion models and linked to detailed DWH cleanup work histories. During the disaster, 34% of participants experienced at least one symptom (23% CNS, 12% PNS); 1-3 years later, 30% did (19% CNS, 17% PNS). Evidence of associations with PM2.5 was most consistent for CNS symptoms (PR range: 1.17 to 1.51), although we did not observe exposure-response trends. For PNS, PR ranged from 0.96 to 1.84. Associations with PM were more apparent among those with lower BTEX-H exposure and among older workers. In a subsample of 328 GuLF Study clinical exam participants, Choi et al. examined blood styrene concentrations and neurobehavioral test results (Behavioral Assessment and Research System and trail making test). Styrene was detected in 77% of participants and findings showed only weak associations and no apparent dose-response relationships between styrene levels and performance on any neurobehavioral tests, although some associations were more prominent in males (Choi et al., 2025, Int J Environ Health Research). Other Environmental Factors Dr. Sandler’s group continued to expand the scope of their investigation into other environmental factors that may adversely impact the health of GuLF Study participants. Analyses leveraged residential geospatial linkages from FEMA’s database on natural hazards, the National Risk Index (NRI). In two separate reports we considered an overall risk score representing 18 natural hazards, and individual scores for hurricanes, heatwaves, coastal flooding, and riverine flooding. In an evaluation of associations with cardiovascular disease-related outcomes, living in an area with higher hurricane risk was associated with a higher prevalence of diabetes and residential heatwave risk was associated with a higher prevalence of diabetes, hypertension, and obesity (Lawrence et al., 2025, STOTEN). For the overall NRI score representing exposure risks for all hazards, the highest quartile of overall NRI was associated with hypertension but not diabetes or obesity. Analyses of poor mental health outcomes (Lawrence et al., 2025, AJE) showed increasing hurricane and coastal flooding scores were associated with depression, anxiety and PTSD in a suggestive exposure-response manner. Associations were strongest for PTSD, with PRs for the highest vs lowest quartile of hurricane and coastal flooding risks of 2.29 (95% CI, 1.74-3.01) and 1.59 (95% CI, 1.23-2.05), respectively. High heatwave risk was associated with anxiety (PR = 1.25; 95% CI, 1.12-1.38) and depression (PR = 1.19; 95% CI, 1.04-1.36) and suggestively with PTSD (PR = 1.20; 95% CI, 0.94-1.52).