Gulf Longitudinal Follow-up (GuLF) Study

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The Gulf Long-term Follow-up Study (GuLF STUDY, www.gulfstudy.nih.gov) 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. We have completed Phase 1 of the Virtual Pooled Registry (VPR) and have been approved by the central IRB (BRANY). We currently have linked National Death Index data through 2022 (12 years of followup data since the spill) and plan to publish findings assessing oil spill cleanup work exposures related to all-cause and cause-specific mortality in early 2024. Extensive efforts were made to characterize the exposures of study participants. We used questionnaire and measurement data that had been 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. TA new measure of dermal hydrocarbon exposure was finalized this year. Two new exposure measures representing exposures to mixtures of volatile organic compounds (VOCs) and a mixture of non-VOC oil related chemicals were also developed and are being linked to participant data. In 2022 we reported associations between oil spill exposures such as PM2.5 from burning and exposure to BTEX-H chemicals (individually and as a mixture) and respiratory health outcomes such as reduced pulmonary function and asthma as well as hypertension and Type 2 diabetes. We are continuing to study these health outcomes including extended follow-up and evaluating changes in biomarkers of these conditions (e.g. hemoglobin A1c ) and blood pressure levels over time. This year we assessed total hydrocarbons and volatile oil components (BTEX-H) in relation to CHD events. Among 22,655 workers without MI diagnoses before the cleanup, 509 reported an incident MI through December 2019. Workers in higher quintiles of each exposure agent had increased coronary heart disease (CHD) risks in comparison with the referent group (quintile 1) of that agent, with the strongest hazard ratios (HRs) observed in the highest quintile (5) (range of HR=1.141.44) (Chen et al., 2023a). We also explored PM2.5 related to in-situ burning and flaring of oil/gas in association with incident CHD events through December 2019. We observed increased CHD hazards among workers with higher levels of average daily maximum exposure (low vs. referent: HR: 1.26, 95% CI: 0.93, 1.70; high vs. referent: HR: 2.11, 95% CI: 1.08, 4.12) (Chen et al., 2023b). In a recent study, we assessed crude oil spill exposures associated with neurological functioning among 2,610 clinical exam participants who completed a battery of neurological function tests at a clinical exam 4-6 years after the spill. We did not find evidence of adverse neurologic effects from crude oil exposures among the overall study population However, among workers 50 years of age, several individual chemical exposures were associated with poorer vibrotactile acuity of the great toe, with statistically significant effects observed in third or fourth quartile of exposures (range of log mean difference in the fourth quartile across exposures: 0.13-0.26 m) (Chen et al., 2023c). In a separate study, we assessed the relationship between exposure to in-situ burning/flaring-related PM2.5 and measures of sensory and motor nerve function among 1,186 OSRC workers who completed the clinical exam. We did not find strong evidence of associations between exposure to PM2.5 and sensory or motor nerve function, although there was a suggestion of impairment based on single leg stance among individuals with high exposure to PM2.5 (Norris et al., 2023). We are currently linking a wide range of geospatial environmental data to the GuLF Study to better understand the influence of other environmental and social exposures on the health of study participants and whether these factors interact with any impacts from the spill. Data include a measure of environment quality and a large climate dataset with historic information on daily temperature, humidity, and solar radiation. Using the census based Area Deprivation Index we assessed neighborhood disadvantage and immune-related illnesses. Among 10,543 home visit participants, we found elevated prevalence ratios (PRs) and 95% confidence intervals (CI) for pneumonia associated with disadvantage in the third (PR: 2.04, 95% CI: 1.04, 4.02) and fourth (PR: 2.00; 95% CI: 1.00, 3.98) quartiles (Patel et al., 2022). Current efforts focus on environmental and neighborhood factors and mental health oucomes including depression, anxiety, and PTSD which we previously linked to oil sill exposures. As part of this effort, we have linked to a Federal Emergency Management Agency database of natural hazards, the National Risk Index, and have submitted a paper for publication assessing residential natural hazard risk in relation to mental health outcomes. We have also assessed mental health outcomes in relation to newly linked satellite-based greenspace data from the Normalized Difference Vegetation Index (NDVI) and modeled ambient air pollution metrics from the Socioeconomic Data and Applications Center (SEDAC). Work assessing solar radiation from Daymet, an Oak Ridge National Laboratory database in relation to depression and distress has also been prepared for submission (. Other work has focused on examining toenail samples from workers as biomarkers of chronic metal exposure (Lin et al., 2023) and evaluation associations between exposure to oil spill chemicals and biomarkers of liver and kidney function.