Cleanup in the Gulf: Oil Spill Dispersants and Health Symptoms in Deepwater Horizon Responders.

Cleanup crews applied approximately 1.8 million gallons of chemical oil dispersant to the Gulf of Mexico following the 2010 Deepwater Horizon oil spill.1 A study in Environmental Health Perspectives explores the relationship between potential exposure to the dispersants used and health complaints in a large cohort of workers who participated in the Deepwater Horizon response and cleanup.2 The results show an association between exposure to two chemical dispersants and self-reported health outcomes.

Previous studies have linked oil spill cleanup work to symptoms including eye and throat irritation, respiratory symptoms, and skin rashes.3,4 Yet until now, none attempted to distinguish between potential effects of dispersants versus crude oil exposure.5 The results reported in the new study held even after adjusting for estimated exposures to crude oil.2

Two Corexit™ brand dispersants were used after the Deepwater Horizon spill, EC9527A and EC9500A. Chemical dispersants lower the surface tension between oil and water. They break up oil slicks into smaller droplets that can be more readily dispersed by wind and waves. Although dispersants have been part of the oil spill cleanup arsenal since the 1960s, no previous spill involved the volume of dispersant use seen in the Deepwater Horizon response and cleanup.6

“It is important to understand the potential toxicity of any chemical released in such large volumes to which workers or the public may be exposed,” says Bernard Goldstein, an environmental toxicologist at the University of Pittsburgh Graduate School of Public Health. Goldstein was not involved in the new research. Most of the research on dispersants to date has focused on marine species.6,7

Crewmen haul an oil-covered boom onto a Coast Guard cutter 18 days after the Deepwater Horizon explosion in April 2010. The GuLF STUDY included more than 30,000 of the Coast Guard personnel, federal employees, contractors, Gulf Coast residents, and volunteers who worked on the Deepwater Horizon response and cleanup. Image courtesy of U.S. Coast Guard.

For the study, between 27,659 and 29,468 oil spill cleanup workers provided responses via a telephone survey about respiratory, skin, and eye irritation symptoms during and after the Deepwater Horizon response. (The number of respondents varied depending on the outcome of interest.) The survey was conducted between 2011 and 2013—one to three years after the spill. All respondents were part of the Gulf Long-term Follow-up Study (GuLF STUDY), an ongoing investigation of potential long-term health outcomes among workers involved in the Deepwater Horizon oil spill cleanup.8

The researchers, led by epidemiologist Dale Sandler of the National Institute of Environmental Health Sciences, used data from the survey to classify participants as exposed to dispersants if they reported having worked directly with chemicals, having worked on a ship from which dispersants were applied, or having spent more than half their time working with any dispersant-related equipment. The exposure measure also took into consideration when and where the participants worked during the cleanup.

After adjusting for estimated co-exposures, including crude oil and other chemical decontaminants, the researchers found that workers with potential exposures to either EC9527A or EC9500A were more likely to report that they experienced certain systems during the cleanup. Dispersant-exposed workers were 61% more likely than unexposed workers to report burning in the nose, throat, or lungs, 58% more likely to report chest tightness, 49% more likely to report eye irritation, and about 40% more likely to report cough or wheeze.

The researchers found a weaker association between potential exposure and symptoms that were present at the time of the telephone survey, many months after the cleanup took place. “Finding that workers with potential exposure to dispersants had acute symptoms during the cleanup was consistent with what we expected based on laboratory studies. It was reassuring that many of those who reported symptoms during the spill no longer had them one to three years later,” Sandler says.

However, she adds, “We were surprised to see that some of the workers who were exposed to dispersants and did not report having symptoms while they were working on the cleanup reported having them when they enrolled in the study.” Sandler explains that people may be better at reporting how they feel in the moment than recalling how they felt in the past, but it is also possible that the association between dispersant exposure and current symptoms is due in part to people overreporting their symptoms.

Sandler points out that it is not clear yet what effect—if any—these symptoms may have on long-term health. “We do not yet know whether exposures during the oil spill will be associated with clinical disease down the road,” she says.

Future research should address “how we can get the most benefit out of dispersants while at the same time minimizing the risk,” Goldstein says. He adds that some attention should be given to the toxicity of mixtures of dispersant and weathered oil. The chemicals and physical properties of oil change as it interacts with sunlight, wind, and microbes in the environment—a process called weathering. “We know very little about the toxicity of these mixtures,” he says.