Monitoring of benzene-exposed workers for genotoxic effects of benzene: improved-working-condition-related decrease in the frequencies of chromosomal aberrations in peripheral blood lymphocytes.

The genotoxic effects of benzene were assessed in peripheral blood lymphocytes of 49 workers occupationally exposed to benzene (3-68.7 mg/m3 in the work environment) for 0-2, 2-10 and more than 10 years (10, 22 and 17 workers, respectively). Chromosomal aberrations, SCEs and UV-induced DNA synthesis were used as indicators of genotoxic effects. Most of the workers were followed up in 1991 and 1992, while the benzene concentrations were reduced to 1-18.4 mg/m3 air. Considered overall, in the "exposed" groups, the frequencies of chromosomal aberrations were significantly higher than in controls thus providing evidence for the clastogenic effects of benzene. However, there seems to be no correlation between aberration frequencies and the duration of prior exposure to benzene. In 1991 and 1992, when the benzene concentrations were brought down, there was a concomitant decrease in the frequencies of chromosomal aberrations; in 1992 the decrease reached one third to one half of the initial frequencies, values still higher than in the controls. With the other genotoxic end-points, the changes were small and not consistent.