A review of the data quality and comparability of case–control studies of low-level exposure to benzene in the petroleum industry
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Published case–control studies of risks of leukaemia following low exposures to benzene in the distribution of petroleum (gasoline) have not all identified the same level of risk, but the studies have had differences in cohort inclusion, case determination and availability of occupational and lifestyle data. We reviewed the quality and comparability of the data from three (of four) studies.
Through site visits, discussions with the investigators and reading study reports, we reviewed and audited the methods used for selecting cases and controls, for estimating individual exposures and for analysing and interpreting the data. Case–control comparisons of exposures were examined using customised graphs.
there were no issues of subject selection, methods or general data quality that were likely to have distorted their internal comparisons;
we could not check in detail whether the metric for exposure assessments was the same across the studies;
the exposure assessments for the Australian study required the least backward estimation, and the Canadian, which also had fewest cases, the most;
evidence of an increased risk at higher exposures in Australia was convincing.
The findings are consistent with some effect of benzene at higher lifetime exposures. A proposed pooled analysis should improve quantification of any exposure–response relationship.
KeywordsPetroleum Benzene Leukaemia
- Armstrong TW, Pearlman ED, Schnatter AR et al (1996) Retrospective benzene and total hydrocarbon exposure assessment for a petroleum marketing and distribution worker epidemiology study. Am Ind Hyg Assoc J 57:333–343Google Scholar
- Glass DC, Gray CN, Jolley DJ et al (2004) Benzene exposure and leukemia (Authors’ Response to Letters). Epidemiology 15:510–511Google Scholar
- Goldsmith B (2004) Benzene exposure and leukemia (Letter to the Editor). Epidemiology 15:509–510Google Scholar
- Greenland S, Schwartzbaum JA, Finkle WD (2000) Problems due to small samples and sparse data in conditional logistic regression analysis. Am J Epidem 151(5):531–539Google Scholar
- Hastie TJ, Tibshirani RJ (1990) Generalized additive models. Chapman & Hall, LondonGoogle Scholar
- IARC (International Agency for Research on Cancer) (2004) IARC monographs on the evaluation of carcinogenic risks to humans, vol 82. IARC, LyonGoogle Scholar
- Institute of Petroleum (2003) Leukaemia risks in relation to benzene exposure. Report of a meeting held on 22nd October 2002, London: Institute of PetroleumGoogle Scholar
- Miller BG, Fransman W, Heederik D et al. (2005) A review of the data quality and comparability of case–control studies of low-level exposure to benzene in the petroleum industry. Edinburgh: Institute of Occupational Medicine. (IOM Research Report TM/05/04). http://www.iom-world.org/pubs/IOM_TM0504.pdf