Estimating the incidence of leukemia attributable to occupational exposure in Iran.

Objective: The aim this study was to estimate the fraction of leukemia incidence in Iran attributable to occupational exposure to benzene, ionizing radiation, and ethylene oxide.

Methods: Nationwide exposure to each of these leukemogens was estimated using workforce data available at the ILO (International Labor Organization) website. The prevalence of exposure to leukemogens in each industry was estimated using exposure data from the CAREX (CARcinogen EXposure) database. The magnitude of the relative risk of leukemia for each leukemogen was from published literature. Using the Levin's population attributable risk (incidence), fractions of leukemia incidences attributed to workplace leukemogens were then estimated.

Results: The total workforce in Iran according to the 1995 census included 12,488,020 men and 677,469 women. Agriculture was the largest sector with 24.5% of the males and 0.27% of the females, and the electricals-related sector was the smallest with 1.16% of the males and 0.66% of the females. After applying the CAREX exposure estimates to each sector, the proportion exposed to leukemogens was 0.016% for male workers and 0.02% for female workers. Estimating a relative risk of 3.6 (95% CI of 3.2-4.2) for high exposure and 1.9 (95% CI 1.7-2.1) for low exposure and employing the Levin's formula, the fraction of leukemia attributed to leukemogens in the workplaces among females was 3.6% (95% CI of 3.1-4.5) and among males was 7.6% (95% CI of 6.4-9.2). These fractions corresponded to estimated incidences of 0.60 (95% CI of 0.50-0.70) and 0.22 (95% CI of 0.16-0.23) cases of leukemia per 100,000 populations for males and females, respectively.

Conclusion: The incidence of leukemia due to occupational exposure is very low in Iran, although males are at greater risk than females.