Linet MS, et al. - Researchers intended to ascertain the link between benzene exposure response and risk of myeloid neoplasms, particularly risks by time since exposure and age at exposure, in Chinese workers. For myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML) arising within 10 years of benzene exposure and for first exposure in the 2 to less than 10-year window before age 30 years, the strongest impacts were seen as far as myeloid neoplasms were concerned.

Methods

• Researchers performed a case–cohort study to assess combined MDS/AML (n=44) and chronic myeloid leukemia (n=18) in 110,631 Chinese workers followed up during 1972–1999.
• They used hierarchical modeling of occupational factors calibrated with historical routine measurements to estimate benzene exposures.
• They used Cox regression to assess exposure response for cumulative exposure and average intensity; P values were two-sided.

Results

• Findings suggested increased MDS/AML risk with increasing cumulative exposure in a priori defined time window (2 to <10 years) before the time at risk (P_trend=08).
• A stronger exposure response (P=.004) was observed for first exposure (within the 2 to <10-year window) before age 30 years, for cumulative exposures of more than 0 to less than 40, 40 to less than 100, and at least 100 ppm-years, compared with no exposure, the rate ratios of 1.12 (95% confidence interval [CI]=0.27 to 4.29), 5.58 (95% CI=1.65 to 19.68), and 4.50 (95% CI=1.22 to 16.68), respectively, were observed.
• Irrespective of age at first exposure, a little evidence of exposure response after at least 10 years (P_trend=.94) was generated.
• Generally similar average intensity results were found.
• Exposed vs unexposed workers had an increased risk for chronic myeloid leukemia, but the risk appeared to increase and then decrease with increasing exposure.