The effect of benzene on white blood cell and red blood cell counts, hemogl
obin level, mean corpuscular volume (MCV) and platelet count was investigat
ed among workers in a small petroleum company. The investigated cohort cons
isted of 105 workers exposed to low levels of benzene between 1967 and 1994
. The average level of benzene exposure per year ranged between 0.14 parts
per million and 2.08 parts per million (8-hour time-weighted average). The
mean complete blood count (CBC) demonstrated values within normal ranges. W
ith the exception of white blood cells, all other CBC values were significa
ntly reduced during the follow-up period. Length of employment was signific
antly related to the changes in MCV and platelet counts. The reductions in
MCV were significant only among workers who had been employed for more than
10 years at this particular company. The findings gf this study suggest th
at low levels of benzene may affect CBC values, CBC values may serve as a u
seful tool for biological monitoring for workers with low-level benzene exp
osure.