Formaldehyde and lymphohematopoietic cancers: A review of two recent studies

Objective: : This paper reviews and evaluates two recent epidemiologic studies of formaldehyde exposure and lymphohematopoietic cancers. One is an update of mortality in a retrospective cohort study of industrial workers and the other is a proportional mortality and case-control study among embalmers. Both studies included subjects with considerable exposure to formaldehyde and both are focused on the myeloid leukemias. Methods: The principal epidemiologic methods and analyses used in the studies are described and evaluated. Additional measures of risk are presented. Results: Neither study reports a significant excess of mortality from any form of lymphohematopoietic cancer. However, both studies are interpreted by their authors as positive for an association between formaldehyde and the myeloid leukemias. This is based on weak and transitory associations seen in exposure-response analyses of relative risks. Issues are raised relating to the interpretation of these findings. Conclusion: There is no statistically significant absolute excess mortality from any lymphohematopoietic cancer in either study. The study of industrial workers showed only a weak and transitory relationship between peak exposure to formaldehyde and the myeloid leukemias. Limited exposure-response relationships for the myeloid leukemias in the case-control study of embalmers apparently have not been analyzed for statistical significance. These limited exposure-response relationships do not provide clear evidence of a causal relationship between formaldehyde and the myeloid leukemias. (C) 2010 Elsevier Inc. All rights reserved.