Reference: Strelitz J, Engel L, Kwok R, et al. 2018. Deepwater Horizon oil spill exposures and nonfatal myocardial infarction in the GuLF STUDY. Environmental Health. 17:69. https://doi.org/10.1186/s12940-018-0408-8
In what appears to be the first study of its kind, researchers detected an association between oil spill exposures and future heart attacks.
In 2010, an explosion on the Deepwater Horizon drilling rig led to the largest marine oil spill in the history of the global petroleum industry. Over 200 million gallons of crude oil polluted the waters of the Gulf of Mexico in the wake of the disaster. Thousands of workers were recruited to face the aftermath. These spill responders were potentially exposed to crude oil, burning oil, cleaning agents, physical exertion, heat, stress, and other factors that could ostensibly impact health.
The GuLF Study
Beginning the year after the disaster, in 2011, the National Institutes of Health (NIH) recruited approximately 33,000 people who were involved in the Deepwater spill response to join the Gulf Long Term Follow-Up Study (GuLF Study). The GuLF study was designed to improve our understanding of the impact of oil spill response and clean-up work on long-term human health.
Previous research on the health consequences of oil spills have mostly focused on the acute, or short-term, impacts. Spill response workers can experience skin and eye irritation, headaches, and acute respiratory problems, and, along with those living in the affected communities, may display symptoms of anxiety and post-traumatic stress. The GuLF study hopes to help understand the potential longer-term health consequences of these spills.
Researchers at the University of North Carolina leveraged the GuLF Study data to assess potential impacts of spill response work specifically on risk of heart attack. They started by excluding those GuLF participants who reported having a heart attack before their work on the oil spill; they wanted to study a seemingly healthy group that wasn’t predisposed to heart conditions. GuLF used extensive telephone interviews with participants to assess a detailed history of their work activities, dates, and locations, along with possible exposure to oil and other chemicals used or released during the spill and its clean-up.
Methods of Exposure Science
In the field of exposure science, researchers are interested in assessing whether an exposure of interest is significantly associated with a change in the prevalence of an outcome of interest. In this case, they want to know if exposure to oil spill response work is associated with increased risk of heart attack. To look at exposure, they looked at whether or not a worker reported doing clean-up work, and, if so, categorized duration of exposure as 1–30 days, 31–90 days, 91–180 days, or > 180 days. They also differentiated between the exposures expected from different types of work and created a matrix to assign workers to maximum total hydrocarbon exposure categories based on their highest exposure task during the clean-up.
The outcome of interest, risk of heart attacks, was measured by self-reported diagnosis of a first, nonfatal heart attack after the clean-up efforts began. Self-report is a limitation of the study; so-called “silent” heart attacks, where the individual is unaware they’ve had one, do happen.
The study team then used a statistical technique called logistical regression to evaluate the risk of the outcome based on the exposures of interest. They tried to hone in on the true effect of the exposure by controlling for other factors that influence risk of heart attack, like age, gender, cigarette use, weight, etc.
What did Researchers Find out?
Out of over 31,100 participants who had not previously experienced a heart attack, 192 reported suffering one after the spill. Of those 192 people, 151 worked specifically on oil spill clean-up. While not statistically significant, the findings do suggest an association between working on the oil spill response and clean-up (vs. not working on clean-up) and nonfatal heart attack, and for living in proximity to the oil spill (vs. away from the spill) with risk of heart attack after adjusting for factors that influence risk of heart attach (like age, weight, etc.).
If exposure to spill response work increases risk of heart attack, we’d expect to see that the workers who did the most work have the most heart attacks, and indeed, the risk increases with duration of exposure, with participants working >180 days showing approximately double the risk compared to those working 1-30 days (although not statistically significant). The study is limited in that there are no actual measurements of exposure levels individual workers experienced. However, the dose-response relationship lends credibility to the findings.
We should take non-statistically significant results with a grain of salt but, we can still gain insight from the findings. Results do suggest that exposure to oil spill work could increase future risk of suffering a heart attack. Public health officials can use this research to help identify the appropriate resources to best support workers who respond to future oil spills. One of the gaps that the next wave of research could target is what specific exposures from oil spill response work might be contributing to increased risk of heart attacks: is it a specific chemical present in the oil or clean-up products? The stress of witnessing environmental catastrophe or losing a home or livelihood? A combination? More research is needed to uncover the answers!