Exposure Assessment of Rayong Oil Spill Cleanup Workers

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 m(3) (336-1200 barrels), washed ashore 1 day later on the island of Samet. We conducted a study to quantify internal dose of polycyclic aromatic hydrocarbons (PAHs) and benzene in 1262 oil spill cleanup workers, and to examine factors related to their dose. Frozen stored urine samples (n = 1343) collected from the workers during the 1 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. 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, cotinine and 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). 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.