Acute high dose exposure to benzene in shipyard workers.

Fifteen degassers were acutely exposed over several days to high concentrations (> 60 ppm) of benzene during removal of residual fuel (degassing) from shipboard fuel tanks. Medical surveillance evaluation mandated by the Occupational Safety and Health Administration's (OSHA) Benzene Standard initially revealed 11 workers (73%) reporting neurotoxic symptoms while degassing. Workers with more than 2 days (16 hours) of acute exposure were significantly more likely to report dizziness and nausea than those with 2 or fewer days of acute exposure. Repeated laboratory analyses performed over a 4-month period after the acute exposure revealed at least one hematologic abnormality consistent with benzene exposure in 9 (60%) of these degassers. One year later, 6 workers (40%) had persistent abnormalities; an additional worker with normal hematologic parameters at the time of our initial evaluation subsequently developed an abnormality consistent with benzene exposure. Numerous large granular lymphocytes were observed on 6 (40%) of the peripheral blood smears. Despite these laboratory findings, there were no significant associations between the presence of hematologic abnormalities and either the number of hours of acute benzene exposure or the duration of employment as a degasser. Volatilization of benzene from the residual fuel was the suspected source of benzene in the headspace of tanks. Confined space exposure to petroleum products may be exposing workers to benzene at levels above the OSHA Short-Term Exposure Limit (STEL). This situation warrants further study.