Respiratory problems and skin conditions, as well as cardiometabolic and mental health issues, appear to disproportionately affect persons who participated in clean up following the Deepwater Horizon oil spill disaster. Such health effects may have been compounded by exposure to previous disasters and may worsen the consequences of future traumas, according to Dale Sandler, Ph.D., chief of the NIEHS Epidemiology Branch. The region’s unique environmental and economic challenges have also contributed.

Sandler presented an overview of published and emerging findings from the GuLF Study as part of the Division of Intramural Research Scientific Director’s Seminar Series, Feb. 26. The study is one of the largest and most comprehensive efforts to understand the health consequences of a major environmental disaster.

“We learned a lot, but there were unique challenges in trying to set up this research program in the middle of a disaster,” said Sandler, who has been leading the GuLF study since its inception.

The GuLF Study

The explosion of the Deepwater Horizon oil drilling rig, April 20, 2010, caused the worst offshore oil spill in history. In the immediate aftermath, 11 workers died and almost five million barrels of crude oil contaminated the water. Within weeks, Sandler met with NIEHS and National Institutes of Health directors to discuss the appropriate research response to the disaster.

Referencing the movie “Deepwater Horizon,” which depicted the immediate aftermath of the rig explosion, Sandler commented that the development period for this project “was also fast-paced, stressful, and round the clock.”

The result was the Gulf Long-term Follow-up Study (GuLF Study), which has examined how nearly 33,000 people who participated in the cleanup efforts were affected physically and mentally. The effort has led to more than 70 peer-reviewed scientific publications to date.

Death rates

The most recent research emerging from the GuLF Study looks at mortality trends in participants using data from the National Death Index, which houses U.S death records. Sandler and her team calculated a metric known as the causal mortality ratio, which divides the observed number of deaths attributed to a particular cause by the expected number of deaths. When they compared this mortality ratio for people who enrolled in the GuLF Study cohort to people in either the Gulf states or the rest of the U.S., they did not see an increase in deaths for the cohort overall.

However, interesting patterns were seen when comparisons were made within the cohort. For example, when the researchers compared those in the cohort who worked on cleanup and a comparison group of persons who trained to work on the spill but were not hired, they found that the death rate from all-causes combined was slightly higher in the exposed workers versus the nonworkers. Those deaths were attributable to certain mental disorders, cardiovascular disease, cancer, and external causes such as fires, accidents, or homicides. Further, death rates for some of these causes appeared to be higher among the workers with the greatest exposure to burning oil and other hazards compared to workers with the lowest oil spill exposures. In analyses of non-fatal events, oil spill exposures have been associated with health effects including anxiety, depression, post-traumatic stress disorder (PTSD), poor respiratory function, asthma, diabetes, heart disease, and hypertension.

According to Sandler, some of these associations were expected based on studies of other disasters, and others were plausible given what is known about high exposure to chemicals found in crude oil.

“But given that this was a short period of exposure, and the exposure levels were not uniformly high, the range and the strength of health effects surprised us, suggesting that other factors could be contributing to enhanced susceptibility,” said Sandler.

Contributing factors

The team suggested that socioeconomic factors and limited health care access could make participants in the GuLF study more susceptible to the negative effects of the oil spill. For example:

• 26% reported incomes less than $20,000.
• 45% reported less than or equal to a high school education.
• 49% lacked access to medical care.
• 49% reported worry about paying rent and 30% worry about paying for groceries.

In addition, the researchers noted that the study population had experienced multiple natural disasters before and after the Deepwater Horizon oil spill. For example, 24% of the cohort reported serious effects from Hurricane Katrina, including displacement, loss of a loved one, or serious injury to self or a loved one. Sandler and her team showed that participants exposed to both disasters had much higher chances of developing anxiety, depression and PTSD, and experienced significantly more physical health symptoms at the time of the spill.

“Disasters often strike the most vulnerable, and their effects are greater among the most vulnerable,” said Sandler.