Workers and volunteers who helped in the clean-up effort after the 2002 Prestige oil spill off the Galician coast of Spain exhibit prolonged respiratory symptoms resulting from their exposure, say researchers from Spain in the first study to examine the long-term effects of such exposures on workers' respiratory health.
The findings were reported in the second issue for September of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
In November 2002, the oil taker Prestige sank off the northwestern coast of Spain, spilling about 67,000 tons of oil that contaminated more than 1,000 kilometers of coastline. More than 100,000 workers and volunteers participated in the clean-up effort. During the first few weeks, clean-up work was done mainly by local fishermen and their families. That initial period was characterized by an "improvisational approach" and a lack of personal protective equipment, according to the study.
Between January 2004 and February 2005, more than two years after the initial disaster, the researchers administered a questionnaire to determine the long-term implications of the clean-up participation on the population of local fishermen who were most directly affected by the disaster. The questionnaire, which could be self-administered or completed through a telephone interview, assessed the fishermen's respiratory problems, use of medication for respiratory problems, and their beliefs and level of anxiety and about the health effects of the spill.
Roughly one-third of the nearly 7,000 respondents were women, who were primarily engaged in shellfish farming. Most of the respondents-- more than half of the women, and two-thirds of the men-- had directly participated in the clean-up efforts for at least one day, most during the first seven weeks of the spill.
"Prevalence rates of lower and upper respiratory tract symptoms were significantly higher in fishermen who had participated in clean-up activities," wrote Francisco Pozo-Rodriguez, M.D., lead investigator of the study.
Overall, the researchers said, clean-up workers were 1.7 times more likely than others to experience lower respiratory tract symptoms. Men who participated in clean-up were twice as likely as those who didn't to have experienced chronic cough or phlegm or asthma in the past year; female clean-up workers were 1.7 times more likely than others to chronic phlegm, and 1.6 times as likely to experience nasal symptoms. Excluding workers who reported anxiety or who believed that their health was adversely affected by the spill, the researchers found that the differences in respiratory symptoms decreased slightly but remained significant.
Importantly, they found that the increased prevalence of upper- and lower-respiratory tract symptoms persisted for more than a year following the last clean-up activity, but while "still significant when more than 20 months had elapsed," rates did show eventual decline, suggesting that the damage may be in part reversible.
There was no association between performing clean-up work and having diagnosed respiratory conditions, such as asthma, leading the investigators to speculate that warnings from health authorities may have discouraged people with known respiratory conditions from participating in the clean up. This self-selection among clean-up participants, the so-called healthy worker effect, "may have led to an underestimation of the risk estimates," wrote Dr. Pozo-Rodriguez.
"To our knowledge, no previous study has explored long-term respiratory effects in clean-up workers of other oil spills. Our findings suggest that participation in clean-up work of oil spills may result in prolonged adverse respiratory health effects 1-2 years after exposure," he continued. "Increasing awareness of the potential chronic respiratory effects among clean up workers of future oil spills, in combination with appropriate hygiene regulations, is strongly recommended."
The cross-sectional design of the study and possible recall bias of the questionnaire's respondents leaves the question of reversibility question an open line of inquiry. To address this possibility, the investigators identified a cohort of prospective subjects to follow for further evaluation of the time-dependent nature of the effects.