Abstract
We examined the frequency of mutant lymphocytes (VFs) in workers (n = 30) occupationally exposed to the petrochemical, 1,3βbutadiene (BD), using the autoradiographic HPRT mutant lymphocyte assay. Current exposures were determined with organic vapor monitors that had a 12βhr method detection limit (MDL) of 2.5 parts per billion (ppb). HPRT VFs were analyzed with respect to current exposure estimates, age in years, and occupational longevity (OL; defined as years working in the BD industry at this facility). Current exposures were low (mean 93.5 ppb, median 2.5 ppb) with only one individual's estimate (1683.5 ppb) exceeding the Occupational Safety and Health Administration's permissible exposure limit of 1,000 ppb. The majority (>50%) of current exposures were below the MDL. HPRT VFs were not significantly associated with current exposures (n = 29), and they were not significantly associated with age (n = 29). HPRT VFs were, however, significantly associated with OL (n = 29, R^2^ = 0.107, P < 0.046). This result suggests that chronic and/or past, highβlevel exposures might leave a mutagenic signature that is revealed by the HPRT assay, possibly through the retention of mutant, longβterm memory Tβcells. While it is encouraging that current occupational exposures to BD in this facility do not appear to be increasing the frequency of mutant Tβlymphocytes, evidence from workers with a lengthy history in the industry (β₯30 years in this case) indicates that these individuals likely require additional biomonitoring for possible mutagenic effects resulting from chronic, past exposures. Environ. Mol. Mutagen., 2009. Β© 2008 WileyβLiss, Inc.