Background: In July of 2013, a pipeline connecting an offshore oil platform to a tanker caused crude oil to spill into the Sea of Rayong off the coast of Thailand. The resulting oil slick, estimated to be between 50 and 190 cubic meters (336-1,200 barrels), washed ashore one day later on the island of Samet. We conducted a study to quantify internal dose of polycyclic aromatic hydrocarbons (PAHs) and benzene in 1,262 oil spill cleanup workers, and to examine factors related to their dose.
Methods: Frozen stored urine samples (n=1343) collected from the workers during the one month cleanup period were used to measure the concentration of 1-hydroxypyrene-glucuronide (1-OHPG), cotinine and creatinine. Data from questionnaires and urinary trans,trans-muconic acid (t,t-MA), a benzene metabolite, measured previously as part of a worker health surveillance plan, were linked with the laboratory data.
Results: The internal dose of urinary 1-OHPG was highest in individuals who worked during the first 3 days of cleanup work (median: 0.97 pmol/ml) and was 66.7% lower (median: 0.32 pmol/ml) among individuals who worked in the final week of the study (days 21-28). After adjusting for age, cotinineand creatinine by regression analysis, the decline in urinary 1-OHPG concentration with days of cleanup remained significant (P-trend <0.001). A decreasing trend by days of cleanup was also observed for detectable urinary t,t-MA percentage (P-trend <0.001).
Conclusion: Rayong oil spill cleanup workers exhibited evidence of elevated levels of PAH and benzene exposure during the early weeks of cleanup, compared to near background levels 4 weeks after cleanup began. Long-term health monitoring of oil spill cleanup workers is advised.
Keywords: PAHs; benzene; biomarkers; cleanup; exposure; oil spill.