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On recent meta-analyses of exposure to glyphosate and risk of non-Hodgkin’s lymphoma in humans

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Abstract

Purpose

A recent meta-analysis of five case–control studies and one cohort study reported that exposure to glyphosate was associated with increased risk of non-Hodgkin’s lymphoma (NHL). The meta-analysis was based on estimates of risk from the included studies at the highest reported exposure level obtained from analyses with the longest lag period. The extent to which the summary estimate depends upon the exposure definitions and assumed latency period is uncertain.

Methods

We carried out sensitivity analyses to determine how the definition of exposure and the choice of latency period affect the summary estimate from meta-analyses of the 6 studies included in the recent meta-analysis. We also conducted a meta-analysis of ever-exposure to glyphosate incorporating the most updated results from the case–control studies.

Results

The summary estimates of risk varied considerably depending on both the assumptions about exposure level and latency. Using the highest reported exposure levels, evidence of an association between glyphosate and NHL was strongest when estimates from analyses in the cohort study with a 20-year lag [RR = 1.41 (95% CI 1.13–1.76)] and a 15-year lag [RR = 1.25 (95% CI 1.01–1.25)] were included. In our meta-analysis of ever-exposure with no lag period, the summary relative risk with updated estimates was 1.05 (95% CI 0.87–1.28).

Conclusion

The results of meta-analyses of glyphosate exposure and NHL risk depend on assumptions made about both exposure level and latency period. Our results for ever-exposure are consistent with those of two recent meta-analyses conducted using somewhat different study inclusion criteria.

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Acknowledgments

Dr. Tarone was deposed in December 2019 as an unpaid fact witness in two January 2020 California trials involving Roundup. The purpose of the deposition was to defend his published papers on the IARC glyphosate classification [3]. Dr. Tarone helped design the Agricultural Health Study and coauthored some early papers based on the study.

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Authors and Affiliations

  1. New Rochelle, NY, USA

    Geoffrey C. Kabat

  2. College of Agricultural and Life Sciences, University of Idaho, Moscow, ID, 83844, USA

    William J. Price

  3. Rockville, MD, USA

    Robert E. Tarone

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  1. Geoffrey C. Kabat
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  2. William J. Price
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Correspondence to Geoffrey C. Kabat.

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All authors declared no potential conflicts of interest. No funding was sought or received for the statistical analyses or for writing the paper.

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Kabat, G.C., Price, W.J. & Tarone, R.E. On recent meta-analyses of exposure to glyphosate and risk of non-Hodgkin’s lymphoma in humans. Cancer Causes Control 32, 409–414 (2021). https://doi.org/10.1007/s10552-020-01387-w

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  • DOI: https://doi.org/10.1007/s10552-020-01387-w

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