Common herbicide glyphosate significantly harms infants’ health in rural areas, new research suggests

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Low birth weight is strongly linked to long-term health problems. (Photo credit: Christian Bowen on Unsplash)

Glyphosate, a synthetic herbicide best known as the active ingredient in Roundup®, has significantly harmed the health of babies in rural U.S. communities over the last two decades—especially those already at risk of poor birth outcomes, new research shows.

Spurred by the introduction of genetically modified seeds by Monsanto in 1996, the use of glyphosate nationwide has increased by more than 750%. In that time, researchers from the University of Oregon estimate that maternal exposure to the pesticide reduced the average birth weight of babies and duration of pregnancy (gestational length) in rural areas, where it is most prevalent.

Low birth weight (less than 5 pounds, 8 ounces) and premature birth (before 37 weeks) are important health indicators because they are strongly associated with short- and long-term outcomes for newborns, including infant mortality, developmental disabilities, and chronic diseases such as diabetes and obesity. They also reflect maternal well-being, as well as the overall health of a population, including access to health care.

The study indicates exposure to glyphosate, at the mean level of 2012 intensity:

“Together, these results indicate that even at the mean level of intensity in the United States, glyphosate exposure significantly deteriorates infant health,” say co-authors Emmett Reynier and Edward Rubin, whose work appears January 21 in Proceedings of the National Academy of Sciences (PNAS). “Our findings, combined with other recent work, challenge the prevailing regulatory position that GM crops and their associated agricultural practices are safe—and even beneficial—for health.”

The impact also disproportionately harmed babies with lower expected birth weights, including those from historically disadvantaged populations, the study shows. 

Infants expected to have low birth weights (less than 5 pounds, 8 ounces), most often female, Black, and/or children of unmarried parents, faced the most severe effects, the study shows. Glyphosate impact was 1.8 times larger for births to non-White mothers compared to White mothers. 

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“These estimates suggest a small subset of the population may bear particularly large health burdens from glyphosate exposure,” the researchers say.  

Mounting evidence of glyphosate’s harms 

Glyphosate (GLY), now manufactured and sold in hundreds of products, is a broad-spectrum herbicide patented in 1974 by Monsanto (now owned by Bayer). More than 20 years later, the company developed genetically modified crops including soybean, corn, and cotton that could withstand direct exposure to the pesticide. This allowed farmers to directly spray glyphosate onto crops, eliminating weeds while sparing the crops themselves—but also allowing some of it to contaminate water, food, soil, dust, and air.

A 2017 study found that Americans’ exposure to glyphosate grew by about 500 percent since Roundup® Ready GMO crops were introduced in the U.S. in 1996, and there has been widespread detection of glyphosate in human urine and blood, including in pregnant women. Federal regulators have maintained “there are no risks to human health from the currently registered uses of glyphosate,” despite a lack of large studies, Reynier and Rubin say.

The new report, however, is consistent with a growing body of scientific literature and recent litigation documenting glyphosate’s harmful impact on the environment and fetal development, the endocrine system, the reproductive system, and the brain. Recently, the first large-scale, population-level studies linked glyphosate exposure—driven by GM seed expansion and transported through rivers—to increased infant mortality and pediatric cancer in Brazil.

“While the study focuses on the health effects of glyphosate, it is worth noting that these effects were allowed by the introduction of a technology: seed genetically modified to be resistant to glyphosate,” says Rubin, an assistant professor at the University of Oregon’s department of economics. “In the absence of GM seed, it is unlikely we would have seen the same intensification of glyphosate exposure in the United States. We removed a natural barrier to over-application of this chemical and then application levels soared.”

Investigating infant health against GM backdrop

To understand how glyphosate impacts health during pregnancy, the University of Oregon researchers compared more than 10 million infant health outcomes in rural US counties (1990–2013) before and after GM seeds were introduced, across areas more and less suitable for growing GM crops. They also considered how glyphosate use increased. Among other factors, the authors controlled for the use of other pesticides.

Limitations include the lack of direct measurement of glyphosate exposure, versus county-level data, the researchers say. They also note more work is needed to better understand the benefits and costs of GM crops, glyphosate, and specific exposure mechanisms underlying their effects and the long-term impacts of these effects.

“The results that glyphosate reduces infants’ health at birth directly conflict with the EPA’s current guidance,” says Rubin. “With a growing body of evidence that glyphosate adversely affects human health, it may be time for the EPA to reconsider its stance.”

Reference

Reynier E, Rubin E. Glyphosate exposure and GM seed rollout unequally reduced perinatal health. Proceedings of the National Academy of Sciences. 2025;122(3). doi:10.1073/pnas.2413013121

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