The wider health effects caused by the explosion and subsequent oil spill of the Deepwater Horizon offshore drilling rig are not fully known. An oil discharge continued in the Gulf of Mexico for 84 days, resulting in the largest oil spill in the history of the petroleum industry, estimated at 206 million gallons (4.9 million barrels). The spill exposed thousands of area residents and cleanup workers to risks associated with oil fumes, particulate matter from Controlled burns, volatile organic compounds (VOCs), polycylic aromatic hydrocarbons (PAHs), and heavy metals.
The spill was also notable for the volume of Corexit oil dispersant used to help disperse the oil. Although approved by the EPA, no toxicology studies had been done at this time. In 2011, a toxicology study was done and it reported 57 chemicals in the ingredients including chemicals associated with cancer, skin irritation from rashes to burns, eye irritation, potential respiratory toxins or irritants; and kidney toxins.
At the height of operations (summer of 2010), response vessels numbered about 7,000 and personnel numbered over 47,000; as of January 2013, that figure has dropped to about 935. The maximum extent of shoreline oiling involved almost 1,100 miles of shoreline and as of December 2012, approximately 339 miles of oiled shoreline remained subject to evaluation and/or cleanup operations.
Acute toxicity symptoms have been reported and the study of long-term medical and psychological effects is ongoing. As the largest marine oil spill in history, the potential for physical, psychological, and socioeconomic difficulties and long term effects remain unknown. Considering the number of residents and clean-up workers exposed, it has been seen as the most demanding on-water response in U.S. history. Only a few studies have looked at long-term health consequences, it is assumed that the spill's impacts are wide-reaching and will have long-lasting effects.
Reports of health effects
People can be exposed to the chemicals in oil by breathing them, swallowing, or touching them. Previous studies show consistent evidence of acute toxic effects, mainly neurological, ocular (eye), and respiratory, of those living in exposed communities and among clean-up workers. While the spill was ongoing the Centers for Disease Control and Prevention (CDC) reported that some residents along the coast reported smelling odors and experiencing nausea, headaches, eye, nose, and throat irritation; however, the CDC said that their tests found that air quality levels for ozone and particulates were normal on the Gulf coastline for that time of year and odor-causing pollutants associated with petroleum products were being found at low levels."
By 21 June 2010, 143 oil spill exposure cases had been reported to the Louisiana Department of Health and Hospitals; 108 of those cases involved workers in the clean-up efforts, while 35 were reported by gulf residents. Writing in The Nation, Antonia Juhasz reported that according to the health departments of Louisiana, Mississippi and Alabama, from June to September 2010, when they stopped keeping track, more than 700 people sought health services with complaints "believed to be related to exposure to pollutants from the oil spill." However, she believed the number to be much higher because in her numerous interviews covering over two years, most people did "not know to report their symptoms as related to the oil spill, nor did their physicians ask."
The National Institute for Environmental Health Sciences is sponsoring a study, "Women and Their Children's Health" (WaTCH), which will follow the health issues of 2,500 women and 800 children living along the Louisiana coast. Initial information gathered from questionnaires answered by 224 women "shows a statistically significant relationship between their reported symptoms and exposure to the spill." In the initial period of exposure, the participants reported "wheezing; tightness in chest; shortness of breath; watery, burning or itchy eyes; stuffy, itchy or runny nose; burning in nose, throat or lungs; skin rash; sore or blisters lasting at least three days; severe headaches or migraines; nausea; excessive fatigue or tiredness; diarrhea; sore throat; and being unable to concentrate."
In another study conducted by the Centers for Disease Control and the Alabama Health Department similar health effects were recorded in two coastal counties in Alabama. A Columbia University study on health effects among children in Louisiana and Florida found that more than 40% of 1,437 parents living less than from the coast had been directly exposed to the spill and more than a third of the parents reported physical or mental health symptoms among their children.
Scientific evidence
Although the spill has resulted in anecdotal evidence of sickness experienced by coastal residents and workers involved in the cleanup, scientific evidence has been scant. The spill differed from previous spills in that the leak was at the ocean floor rather than on the surface and the volume of oil spilled and the amount of dispersant used was unprecedented. The Louisiana state health officer stated, "This is more than a spill. This is ongoing leakage of a chemical, and adding chemicals to stop the chemicals. We're feeling like we're in a research lab." Moreover, the proximity to populated communities, the number of potentially exposed workers and community members, and the duration of the spill were far greater than any previously studied oil spills. Of more than 40 prior major oil spills, only 8 led to studies of health effects and only two of them included any long-term follow-up. According to the researchers at the National Institute of Environmental Health Sciences, early data from the two long-term studies "suggested that respiratory and genotoxicity effects were important to capture, as well as mental health outcomes commonly associated with disasters of this scale."
In June 2010, at the request of the US Department of Health and Human Services, the U.S. National Academies Institute of Medicine held a workshop to discuss known health effects of previous oil spills and how they might apply to the Gulf spill and to coordinate epidemiological monitoring and ongoing medical research. On the second day of the meeting the suicide of William Allen Kruse, a charter boat captain working as a BP clean-up worker, intensified previous expert commentary on the current and likely long-term mental health effects of the ongoing crisis. David Abramson, director of research for Columbia's National Center for Disaster Preparedness, noted the increased risk of mental disorders and stress-related health problems. In August, the group released their conclusions in a report, "Workshop Summary: Assessing the Effects of the Gulf of Mexico Oil Spill on Human Health".
In 2011 the Louisiana State University Health Sciences Center did a study to compare the acute health impacts of the spill with the acute health impacts reported from previous spills to predict health impacts in Louisiana as compared with the health impacts reported from prior crude oil spills. The study reported that "Acute health effects in cleanup workers mirrored those reported in cleanup workers following prior oil spills as ranked by systems (and by symptoms)." The study advised that affected individuals "will require long-term surveillance for chronic adverse health effects including cancer, liver and kidney diseases, mental health disorders, and fetal alcohol spectrum disorders."
According to a Newsweek report, cleanup workers were not provided safety equipment by the company, and the safety manuals were "rarely if ever" followed, or distributed to workers. The safety manuals read: "Avoid breathing vapor" and "Wear suitable protective clothing." In 2013, Susan Shaw of the Deepwater Horizon oil spill Strategic Sciences Working Group, stated in an Al Jazeera article, "BP told the public that Corexit was 'as harmless as Dawn dishwashing liquid' ... But BP and the EPA clearly knew about the toxicity of the Corexit dispersants long before this spill." According to Shaw, BP's own safety sheet on Corexit reported that there were "high and immediate human health hazards". The same Al Jazeera article also reported on a study that was published in 2013 in The American Journal of Medicine that reported significantly altered blood profiles of individuals exposed to the spilled oil and dispersants that put them at increased risk of developing liver cancer, leukemia and other disorders; however, BP disputed the methodology of the study and cited federal studies that BP said contradicted the report and supported the company's position that the dispersants did not create a danger to health.
Although most studies relating to Corexit focus mainly on its effectiveness as a dispersant, public pressure to evaluate its safety towards humans after the oil spill and response clean up brought about several studies about the health effects of Corexit, both alone and in conjunction with spilled oil.
In a cohort study that surveyed United States Coast Guard workers who participated in the gulf spill clean up efforts, a dose–response relationship was found between duration of exposure to oil and dispersant and respiratory symptoms including coughing, wheezing, and shortness of breath. Exposure to both oil and dispersant as opposed to just oil was associated with even higher rates of these respiratory issues. The authors also acknowledge that their results on the increased effect of oil and dispersant together are supported by Liu et al., 2016, and that their findings on the specific symptoms associated with dispersant exposure are supported by McGowan et al., 2017.
Studies on the health effects of the oil dispersant Corexit are careful to distinguish between the two types used during the BP oil spill: EC9500A and EC9527A, as some of the research shows differential interactions with oil and different impacts on human symptoms. Although the US EPA completed a series of trials on determining the toxicity of EC900A, which concluded it was “slightly toxic” or “practically non-toxic”, they did not evaluate the toxicity of EC9527A. Even with EX9500A, subsequent studies have shown that it does exhibit toxic effects, and more studies are evaluating the potential toxicity of both types of Corexit, both alone, or in conjunction with spilled oil.
One such epidemiological study showed a statistically significant increase in risk of mild respiratory illness among those exposed to Corexit 9500 and 9527, even after controlling for various factors including oil exposure. Burning in the eyes, the throat, lung, and nose, and tightness in the chest were the most significant values.
NIOSH Health Hazard Evaluations In May 2010, the National Institute for Occupational Safety and Health (NIOSH) was contacted by BP to conduct a health hazard evaluation (HHE), following the hospitalization of several fishermen working under BP's Vessels of Opportunity (VoO) program. The VoO program involved the temporary hire of local out-of-work fishermen to remove oil from the Gulf of Mexico, particularly using booming and skimming tactics. The HHE focused on all major offshore response activities, such as booming, skimming, releasing oil dispersants, in situ burning, and general containment and removal of oil. Sampling conducted to test for a wide array of chemicals, gases, particulates, and metals emitted in the offshore work showed that the substances were either undetectable or were below individual occupational exposure limits.