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Exposure to benzene at work and the risk of leukemia: a systematic review and meta-analysis

Khalade, Abdul and Jaakkola, Maritta S and Pukkala, Eero and Jaakkola, Jouni JK (2010) Exposure to benzene at work and the risk of leukemia: a systematic review and meta-analysis. Environmental Health, 9 (1). p. 31. ISSN 1476-069X

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URL of Published Version: http://dx.doi.org/10.1186/1476-069X-9-31

Identification Number/DOI: doi:10.1186/1476-069X-9-31

Background
A substantial number of epidemiologic studies have provided estimates of the relation between exposure to benzene at work and the risk of leukemia, but the results have been heterogeneous. To bridge this gap in knowledge, we synthesized the existing epidemiologic evidence on the relation between occupational exposure to benzene and the risk of leukemia, including all types combined and the four main subgroups acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML).

Methods
A systematic literature review was carried out using two databases 'Medline' and 'Embase' from 1950 through to July 2009. We selected articles which provided information that can be used to estimate the relation between benzene exposure and cancer risk (effect size).

Results
In total 15 studies were identified in the search, providing 16 effect estimates for the main analysis. The summary effect size for any leukemia from the fixed-effects model was 1.40 (95% CI, 1.23-1.57), but the study-specific estimates were strongly heterogeneous (I2 = 56.5%, Q stat = 34.47, p = 0.003). The random-effects model yielded a summary- effect size estimate of 1.72 (95% CI, 1.37-2.17). Effect estimates from 9 studies were based on cumulative exposures. In these studies the risk of leukemia increased with a dose-response pattern with a summary-effect estimate of 1.64 (95% CI, 1.13-2.39) for low (< 40 ppm-years), 1.90 (95% CI, 1.26-2.89) for medium (40-99.9 ppm-years), and 2.62 (95% CI, 1.57-4.39) for high exposure category (> 100 ppm-years). In a meta-regression, the trend was statistically significant (P = 0.015). Use of cumulative exposure eliminated heterogeneity. The risk of AML also increased from low (1.94, 95% CI, 0.95-3.95), medium (2.32, 95% CI, 0.91-5.94) to high exposure category (3.20, 95% CI, 1.09-9.45), but the trend was not statistically significant.

Conclusions
Our study provides consistent evidence that exposure to benzene at work increases the risk of leukemia with a dose-response pattern. There was some evidence of an increased risk of AML and CLL. The meta-analysis indicated a lack of association between benzene exposure and the risk of CML.

Type of Work:Article
Date:2010 (Publication)
School/Faculty:Colleges (2008 onwards) > College of Medical & Dental Sciences
Department:Institute of Occupational and Environmental Medicine
Subjects:RC0254 Neoplasms. Tumors. Oncology (including Cancer)
RA Public aspects of medicine
Institution:University of Birmingham
Copyright Holders:University of Birmingham, BioMed Central
ID Code:509
Refereed:YES
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