In
the pooled population, the frequency of HFCs showed a statistically significant upward trend at increasing blood lead levels
( x2 for trend = 27.8, p < O.OOOl). A complex relationship between SCEs and benzene exposure was observed, with an
increased frequency of HFCs in the medium exposure intensity class (RR = 1.5. 95% CI = 1.2-1.7). and no difference for
exposure to higher benzene levels (RR = 1.0. 95% CI = 0.9-I.%, compared to reference subjects