Epidemiological studies of formaldehyde exposure and risk of leukemia and nasopharyngeal cancer: A meta-analysis

Abstract

The authors conducted meta-analyses of the epidemiological literature on formaldehyde exposure and risk of leukemia and risk of nasopharyngeal cancer. The authors abstracted study results and confounder information from cohort and case-control studies, and used quantile plots and regression models to evaluate heterogeneity and possible publication bias. No evidence of serious heterogeneity or publication bias was seen. For leukemias, the summary relative risk (RR) was 1.05 (95% confidence interval [CI]: 0.93, 1.20) for cohort studies, and the summary odds ratio (OR) was 0.99 (95% CI: 0.71, 1.37) for case-control studies. Based on cohort and case-control studies, no significant differences were seen by leukemia subtype, job type, publication period, or region. Summary estimates for nasopharyngeal cancers were not elevated after excluding a single plant with an unexplained cluster of nasopharyngeal cancers (cohort RR = 0.72, 95% CI: 0.40, 1.28). The summary estimate was increased for case-control studies overall, but the summary OR for smoking-adjusted studies was 1.10 (95% CI: 0.80, 1.50). Previous meta-analyses showed elevated summary estimates for leukemia; however, these analyses included results from proportionate mortality studies and did not explore other factors that could influence or confound results. By limiting analyses to stronger case-control and cohort study designs, considering the effects of smoking and ignoring anomalous results from a single plant, our meta-analyses provide little support for a causal relationship between formaldehyde exposure and leukemia or nasopharyngeal cancer.

Keywords::

• Cancer risks
• formaldehyde
• leukemias
• meta-analysis
• nasopharyngeal cancer

Acknowledgements

We wish to acknowledge the assistance of Ms. Mona Pion for obtaining articles for review and meta-analyses. We also are grateful to the four anonymous reviewers for their careful review and numerous helpful questions and comments on an earlier version of this report.

Declaration of interests

Support for this work was provided by the Formaldehyde Council, Inc. Dr. Annette Bachand is a part-time employee of ENVIRON and Colorado State University. All other authors are full-time employees of ENVIRON International Corporation, a consulting firm providing services in environmental and health sciences matters to private firms, trade organizations, and government agencies. The authors carried out this work as a normal part of their employment activities. None of the authors has testified in any litigation or regulatory matter concerning formaldehyde. The authors have sole responsibility for the writing and content of the paper, which may not necessarily reflect the views of the Formaldehyde Council, Inc.