RAYONG OIL SPILL CLEANUP WORKERS EXPOSURE AND SYMPTOM ASSESSMENT
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In July of 2013, a pipeline connecting an offshore oil platform to a tanker, operated by PTT Global Chemical (PTTGC), a corporation owned by the government of Thailand, leaked and caused crude oil to spill into the Sea of Rayong off the coast of Thailand. The crude oil covered an area of approximately 20 square kilometers and washed ashore on the island of Samet in an area called “Ao Prao” on 28 July, 2013. On-land cleanup lasted about a month and was performed by a combination of territorial defense volunteers, citizen volunteers, Thai military personnel and PTTGC employees. Cleanup procedures included oil containment and dispersal using absorbent pads, and removal and disposal of contaminated soil, sand and rocks. The goal of this dissertation is to determine if Rayong oil spill cleanup workers were exposed to elevated levels of PAHs and benzene and if these exposures are associated with recorded acute symptoms. We measured the concentration of 1-hydroxypyrene-glucuronide (1-OHPG), a metabolite of pyrene, in the 1,343 frozen stored urine samples available from the cleanup workers, and retrieved previously measured trans,trans-muconic acid (t,t-MA) data, a benzene metabolite. This allowed us to quantify the internal dose of polycyclic aromatic hydrocarbons (PAHs) and benzene in these workers and to examine factors related to their dose. During the early days of cleanup, urinary 1-OHPG of the workers was elevated, comparable to occupational exposures, and declined to near background (general population) levels in workers by the end of the cleanup operation. This was consistent with our hypothesis that the exposure levels of PAHs would be the highest in the first week of cleanup and decline thereafter. Detectable levels of t,t-MA also exhibited a decreasing trend over the course of the cleanup period. Job descriptions with the highest levels of urinary 1-OHPG after adjustment were oil dispersant applicators and contaminated sand/trash handlers. Prevalence of several post-shift symptoms, including irritation of throat and nose, increased with concentration of urinary 1-OHPG. Similarly, one group of symptoms determined by factor analysis, designated as “irritative symptoms”, including irritation of the eye, throat and/or nose, eye injection (redness) and excessive tearing (epiphora) was associated with increased concentration of urinary 1-OHPG. In 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. These workers also demonstrated an association between prevalence of acute irritative symptoms and PAH exposure measured by urinary 1-OHPG. Long-term health monitoring of oil spill cleanup workers should be implemented, particularly among those workers suspected of sustaining high exposure to crude oil.