Formaldehyde exposure not linked to leukemia, research shows

Some scientific reports have a profound impact on government policy. Sometimes, however, there are significant shortcomings in the research - yet the policy impact continues. Critically analyzing scientific research that underlies regulatory decision making and generating new information to ensure decisions are based on sound science are crucial. A recent analysis by Checkoway et al. has been awarded the Kammer Merit in Authorship Award for its review of the data from a critical epidemiological study used by scientific agencies to assess health risk from formaldehyde exposure. The findings from Checkoway et al call into question the original study's conclusions; the analysis further demonstrates the importance of data availability, research reproducibility and adherence to study design when drawing scientific conclusions.

The Kammer Merit in Authorship Award recognizes an outstanding scientific contribution published in the American College of Occupational and Environmental Medicine (ACOEM's) Journal of Occupational and Environmental Medicine (JOEM) during a given year. The winning paper, titled Formaldehyde Exposure and Mortality Risks from Acute Myeloid Leukemia and Other Lymphohematopoietic Malignancies in the US National Cancer Institute Cohort Study of Workers in Formaldehyde Industries, concluded that there is no epidemiological evidence from the National Cancer Institute (NCI) cohort supporting an association between formaldehyde exposure and acute myeloid leukemia (AML). The award was announced late last week.

"The findings from this analysis do not support a finding that formaldehyde exposure is a cause of leukemia," said Harvey Checkoway, Ph.D., lead author of the reanalysis and Professor of Family Medicine & Public Health at the University of California, San Diego. "This reanalysis identifies how critical data interpretation is, given that the risk assessments that rely on these analyses ultimately set occupational and environmental exposure standards."

Checkoway and his colleagues performed analyses of raw data in an attempt to replicate findings reported from a NCI cohort mortality study of workers from 10 US plants producing or using formaldehyde. The NCI study has been influential in the classification of formaldehyde as a human leukemogen by the International Agency for Research on Cancer (IARC) and the National Institute of Environmental Health Sciences (NIEHS) National Toxicology Program (NTP).

In the original analysis, NCI investigators defined "peak" exposure to formaldehyde on a relative basis with respect to individual workers' exposures histories. This complicates data interpretations. Using this definition, analyses of updated mortality data for the NCI cohort reported tentative associations of "peak" exposures with myeloid leukemia (ML) and Hodgkin lymphoma (HL) that are inconsistent with other studies. The new research found no association between acute myeloid leukemia (AML) and cumulative, average or frequency of "peak" exposures. This became clear in the new analysis where AML and chronic myeloid leukemia (CML) were evaluated separately, as two types of leukemia are different diseases and have different risk factors.

The award-winning Checkoway et al. study conducted more comprehensive analyses of associations of specific lymphohematopoietic malignancies (LHM), especially AML, with peak exposure, using a standard definition of peak exposure. Peak was defined in terms of absolute exposure dose and duration, which permitted direct comparisons among similar studies, strengthening the analysis. Checkoway et al. concluded that no clear associations for peak or cumulative formaldehyde exposures were observed in this cohort for any of the specific LHM, including AML

The result of this analysis adds to the weight of evidence that formaldehyde exposure in the workplace does not cause AML, the LHM of greatest concern. It also underscores the need to ensure new information is effectively considered and incorporated into chemical assessments by IARC, NTP and other agencies. "Having this work recognized by ACOEM as a significant contribution in occupational medicine shows how important these findings are to understanding and interpreting the formaldehyde science," said Kimberly White, Ph.D., Senior Director of the American Chemistry Council Formaldehyde Panel.

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