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August 24, 2010 — Oil spill clean-up workers face an increased risk for lower respiratory tract symptoms, indicating that exposure to oil sediments may have detrimental health effects, a new study suggests.
The results are published online today in the Annals of Internal Medicine.
"More than 2.2 billion metric tons of oil are shipped by tanker every year around the world by a fleet comprising more than 11,000 oil tankers. Between 1974 and 2008, more than 9,000 tanker incidents were reported, among which 348 resulted in spills of more than 700 tons of oil," write Gema Rodriguez-Trigo, MD, from Complexo Hospitalario Universitario A Coruña, Spain, and colleagues. "Consequences of oil spills are usually evaluated in terms of environmental damage, effects on marine species and economic losses, but relatively little is known about the effects of oil exposure on humans."
According to the article, volatile organic oil compounds such as benzene are carcinogenic in humans and have been linked to hematological malignancies, and exposure to polycyclic aromatic hydrocarbons damages the skin and mucous membranes and has been linked to skin tumors.
In 2002, the oil tanker Prestige spilled more than 67,000 tons of bunker oil, heavily contaminating the coast of Galicia in northwestern Spain. More than 300,000 volunteers participated in clean-up activities, including a large number of local fishermen.
The aim of this study was to assess respiratory effects and chromosomal damage in these fishermen 2 years after exposure.
The cross-sectional study included 501 local fishermen who were highly exposed to clean-up and compared their health with that of 177 fishermen who were not exposed.
The investigators studied changes in lung function, assessed respiratory markers of oxidative stress and airway inflammation in exhaled breath condensate, and assessed chromosomal damage for increased malignancy risk.
They found that compared with nonexposed fishermen, those exposed to oil were at increased risk of having lower respiratory tract symptoms (risk difference [RD], 8.0; 95% confidence interval [CI], 1.1 - 14.8) 2 years after participating in cleaning up the oil spill. However, there were no differences in tests of breathing function between exposed and nonexposed fishermen.
The researchers also found that the exposed fishermen had increased rates of biomarkers of pulmonary oxidative stress and growth factor activity, suggesting persistent lung damage.
Nonsmoking fishermen had higher exhaled 8-isoprostane levels compared with nonexposed fishermen (geometric mean ratio, 2.5; 95% CI, 1.7 - 3.7). They also had higher exhaled vascular endothelial growth factor (RD, 44.8; 95% CI, 27.9 - 61.6) and basic fibroblast growth factor (RD, 16.0; 95% CI, 3.5 - 28.6).
Structural chromosomal alterations — predominantly unbalanced alterations — were also more prevalent in exposed fishermen (RD, 27.4; 95% CI, 10.0 - 44.8).
The risk of developing any abnormal measure increased with intensity of exposure to clean-up work, the authors write.
The study is limited by the fact that no tests were available for the fishermen before the oil spill, and therefore the investigators cannot be sure that the changes in respiratory symptoms and other abnormalities did not already exist before exposure to the oil spill. Also not known is whether the abnormal tests mean that disease will develop later in life. Finally, the authors note that their findings may not apply to spills involving other types of oil or to different populations of oil spill clean-up workers.
For example, the recent 2010 Deepwater Horizon spill in the United States was made up of crude oil. Although the main components of the Prestige and Deepwater Horizon spills are presumably similar, “proportions of those components (eg. volatile organic compounds, polycyclic aromatic hydrocarbons, hydrogen sulfide gas, heavy metals) are likely different, as might be dispersants to break up the oil slick and the proportion of oil that evaporates and could be inhaled by humans,” the authors explain.
With that said, the researchers conclude, "Our findings indicate that exposure to oil sediments, even for short periods of time, may have detrimental health effects."
What Does the Future Hold for Oil Spills and the Clean-Up Process?
More oil spills will occur, and it is crucial that those who are responsible for organizing clean-up operations take measures to protect the health of the individuals involved. Registries should also be established to assess adverse health outcomes in exposed workers over time, the study authors write.
In an accompanying editorial, David A. Savitz, MD, from Brown University, Providence, Rhode Island, and Lawrence S. Engel, MD, from Memorial Sloan Kettering Cancer Center, New York City, write that litigation and economic consequences follow environmental disasters, and data from research on the disaster's health effects will be used as ammunition in such litigation. For this reason, they write, researchers need to ensure that scientific evidence is generated and disseminated in an "objective, transparent manner."
The Prestige oil spill "reminds us of the importance of incorporating measurement of both biomarkers and clinical outcomes," the editorialists write in their concluding remarks.
"As the research about the health effects of the Deepwater Horizon spill begins, we have seen improved efforts to provide safety training to clean-up workers and a deeper appreciation that the scope of 'the disaster' includes psychological and economic effects on health. As researchers assume their rightful place among the responders to the Deepwater Horizon oil spill, they must be aware that their studies will provide much-needed information for the affected communities as well as for future communities who suffer similar calamities."
The study was funded by Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation. Two study authors were supported by grants from the Instituto de Salud Carlos III, European Regional Development Fund. The other study authors have disclosed no relevant financial relationships.
Ann Intern Med. Published online August 24, 2010.
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