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. 2023 Jan;96(1):1-26.
doi: 10.1007/s00420-022-01878-0. Epub 2022 May 23.

Systematic literature review of the epidemiology of glyphosate and neurological outcomes

Ellen T Chang  1   2 , Nnaemeka U Odo  3 , John F Acquavella  4
Affiliations

Systematic literature review of the epidemiology of glyphosate and neurological outcomes

Ellen T Chang et al. Int Arch Occup Environ Health. 2023 Jan.

Abstract

Purpose: Human health risk assessments of glyphosate have focused on animal toxicology data for determining neurotoxic potential. Human epidemiological studies have not yet been systematically reviewed for glyphosate neurotoxicity hazard identification. The objective of this systematic literature review was to summarize the available epidemiology of glyphosate exposure and neurological outcomes in humans.

Methods: As of December 2021, 25 eligible epidemiological studies of glyphosate exposure and neurological endpoints were identified and assessed for five quality dimensions using guidance from the U.S. Environmental Protection Agency. Studies that assessed personal use of glyphosate were prioritized, whereas those assessing indirect exposure (other than personal use) were rated as low quality, since biomonitoring data indicate that indirect metrics of glyphosate exposure almost always equate to non-detectable glyphosate doses.

Results: Overall, the scientific evidence on glyphosate and neurotoxicity in humans is sparse and methodologically limited, based on nine included epidemiological studies of neurodegenerative outcomes (two high quality), five studies of neurobehavioral outcomes (two high quality), six studies of neurodevelopmental outcomes (none high quality), and five studies of other and mixed neurological outcomes (one high quality). The five high-quality studies showed no association between glyphosate use and risk of depression, Parkinson disease, or peripheral nerve conduction velocity. Results were mixed among the eight moderate-quality studies, which did not demonstrate consistent associations with any neurological endpoints or categories. Low-quality studies were considered uninformative about possible neurotoxic effects due primarily to questionable assessments of indirect exposure.

Conclusions: No association has been demonstrated between glyphosate and any neurological outcomes in humans. To move the state of science forward, epidemiological studies should focus on scenarios involving direct and frequent use of glyphosate while collecting information on validated health outcomes, concomitant agricultural exposures, and relevant personal characteristics.

Keywords: Epidemiology; Glyphosate; Nervous system diseases; Neurotoxicity; Systematic review.

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Conflict of interest statement

This work was sponsored by the Glyphosate Renewal Group (http://www.glyphosate.eu), a European consortium of glyphosate registrants seeking the European Union Annex 1 Renewal of glyphosate. Current members of the Glyphosate Renewal Group are Albaugh Europe SARL, Barclay Chemicals Manufacturing Ltd., Bayer Agriculture bvba, Ciech Sarzyna S.A., Industrias Afrasa S.A., Nufarm GMBH & Co.KG, Sinon Corporation, and Syngenta Crop Protection AG. All costs were shared equally across the member companies in the Glyphosate Renewal Group, through a contract with Bayer AG. The study sponsor’s personnel did not review or comment on any drafts or versions of the manuscript prior to journal submission. ETC provides consulting support for Bayer, a manufacturer of glyphosate-based products that acquired Monsanto, the original glyphosate registrant, in 2018. ETC also formerly provided consulting support for Monsanto and Syngenta. ETC and NUO are employed by Exponent, a science and engineering consulting company that provides consulting support on various topics for members of the Glyphosate Renewal Group. JFA worked on this project as a paid consultant to Exponent. He was formerly employed by Monsanto during the period 1989–2004 and has provided consulting support for Bayer on glyphosate epidemiology and biomonitoring.

Figures

Fig. 1
Fig. 1
Literature search flow chart
See this image and copyright information in PMC

References

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    1. ATSDR (2020) Toxicological Profile for Glyphosate. Agency for Toxic Substances and Disease Registry (ATSDR), U.S. Department of Health and Human Services, Atlanta, Georgia - PubMed

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