CHROMOSOME-ABERRATIONS AND RESPONSE TO GAMMA-RAY CHALLENGE IN LYMPHOCYTES OF WORKERS EXPOSED TO 1,3-BUTADIENE

An integrated population monitoring study was initiated to investigate whether occupational exposure to current low levels of butadiene is m utagenic to workers. Ten exposed workers (mean production area concent ration of 3.5 ppm) and 10 matched plant controls (mean exposure to 0.0 3 ppm) were selected and blood samples were collected for our study. T he standard cytogenetic assay was used to determine chromosome aberrat ion frequencies. In addition, a challenge assay was used to determine response to gamma-rays as an indication of DNA repair deficiencies. In the latter assay, cells were exposed to gamma-rays at the G1 phase of the cell cycle in vitro and the frequencies of chromosome aberrations in the first post-irradiation metaphase cells were quantitated. Based on results of the cytogenetic assay, the exposed group had a higher f requency of cells with chromosome aberrations and higher chromatid bre aks per 100 cells compared with the control. However, the difference w as not significant (p > 0.1). With the challenge assay, the exposed gr oup had a higher frequency of aberrant cells (p < 0.04), chromatid bre aks (p < 0.05), deletions (p < 0.07), and dicentrics (p < 0.02) than t he controls. In addition, the dicentric frequencies from workers were significantly correlated with the presence of a butadiene metabolite [ 1,2-dihydroxy-4-(N-acetylcysteinyl-S)butane] in urine with a correlati on of coefficient of 0.6 (p < 0.01). Two outliers were identified and our interpretation of their responses will be discussed. This study in dicates that the workers had exposure-induced mutagenic effects. Toget her with the observation of gene mutation in a subset of the present p opulation, this study indicates that the current occupational exposure to butadiene may not be safe to workers.