Glyphosate is a chemical found in weed killer products like RoundUp^TM used on farms and home lawns. Because of its effectiveness, glyphosate has become the most widely used herbicide in the world. People who work with these products and people who live near farms where they are used can get exposed to glyphosate through the air. The International Agency for Research on Cancer (IARC) has concluded that glyphosate exposure probably causes blood cancers. 81% of American adults and children have detectable concentrations of glyphosate in their urine. While much is still unknown about the potential health risks of glyphosate exposure, two recently published studies illuminate how big a concern it may be for both workers and the public.

One study aimed at assessing the potential cancer risk posed to farmers who work with glyphosate-containing herbicides. The study used data from the Agricultural Health Study (AHS), which collected biological samples from private and commercial pesticide applicators in Iowa and North Carolina from 1993-1997. The study analyzed AHS participants who were male, above the age of 50, had no blood disorders, and had not been diagnosed with cancer, which created a sample of 1,681 people. The researchers analyzed the DNA of these participants to look for the loss of large portions of DNA in the Y chromosome. Significant loss of DNA portions can have a massive effect on how the body’s cells function and have been linked to increased risk for cancer. Losses of large portions of DNA in the Y chromosome have been specifically linked to blood cancers like those that may be caused by glyphosate exposure.

In the study, 21% of participants had lost large portions of the DNA in their Y chromosome in some of their cells. Statistical analysis found that using glyphosate-containing pesticides for either a longer period or with more intensity were both associated with more DNA loss in the Y chromosome. While these findings do not prove that occupational exposure to glyphosate causes cancer, they provide important biological evidence that glyphosate exposure can cause the kinds of largescale changes in DNA that are associated with cancer. It is the first study of agricultural workers to show this association between glyphosate and DNA loss.

A second study sought the extent of glyphosate exposure among people who live near farms where glyphosate is used. Some studies have shown that glyphosate exposure during pregnancy is associated with reduced fetal growth and pre-term birth. Thus, this study focused on measuring glyphosate levels of pregnant people in Idaho who live near farms that use glyphosate. The study included 40 participants in Idaho who were in their first trimester of pregnancy in 2021. Researchers collected weekly urine samples from participants until delivery. Half of participants lived near farms (less than 0.5 kilometers from a farm) and half lived far from farms (more than 0.5 kilometers from a farm). About two-thirds of both groups had detectable concentrations of glyphosate in their urine.

For participants living near farms, the frequency and concentration of glyphosate detection in urine increased significantly during the pesticide spray season (from May to August) compared to the non-spray season. This change did not occur in participants living far from farms, indicating that increased exposure to glyphosate was likely a result of pesticide spraying. While these findings do not directly track the health effects on pregnant participants or their infants, it is important biological evidence that agricultural use of glyphosate exposes nearby residents. It is the first study to demonstrate that residential proximity to farms using glyphosate is associated with increased glyphosate in the body.

These two studies demonstrate that glyphosate may pose risks to both workers and the public. CHEJ has previously written about the uses and health risks of glyphosate here.