How Herbicides Impact Our Bodies

The widespread use of dicamba impacts more than just our fields

Jan 06, 2023

By 2016, farmers in the Midwest knew what was coming: the weeds in their fields were increasingly resistant to Roundup, the herbicide most of them used in corn and soybean fields to control unwanted guests. For one, Palmer Amaranth—a plant that can grow to 10 feet in height and produce up to 250,000 seeds per plant—was taking hold in row crop fields, and there was little farmers could do to fight back.

Until, that is, Dicamba and 2,4-D were reintroduced.

Both chemicals were herbicides made legal decades prior, and with a little tweaking, rebranding and marketing, farmers were sold on the next best thing, a “new” product to spray on their fields. Monsanto (now owned by Bayer) added dicamba to glyphosate (the active ingredient in Roundup) creating “Xtend” while BASF concocted its own version, Engenia.

green plants on green grass field under blue sky during daytime — Soybean field. Photo by Braden Egli on Unsplash

And then came the complaints. As dicamba products grew in popularity, so too did problems for farmers NOT using the chemical. Since 2017 there have been thousands of reports of dicamba herbicide drifting off of one farm and damaging a neighbor’s crops. From grapes to sweet potatoes to rice, it turns out that not only can dicamba destroy weeds on a farmer’s fields, it can also easily volatilize into the air and travel outside of a farm’s boundaries, harming any plant not genetically modified to resist its wrath.

But now a study is finding that it’s not only the neighbor’s non-GMO soybeans and trees that may be suffering; dicamba and 2,4-D are also showing up in high levels in human urine. In one of the first projects of its kind, the Heartland Study by the Heartland Health Research Alliance (HHRA) is comparing urine samples from 2013 to those taken after the widespread growth in use of dicamba.

“We believe data already generated from urine samples point pretty clearly that exposure in the heartland to dicamba is likely from the air,” Charles Benbrook, Executive Director of the HHRA (and an expert witness in Roundup-NHL litigation) told me when we discussed the study on the phone. “ I cannot think of any other plausible explanation why there is a three-fold increase in average levels of dicamba [in human urine].”

According to the National Pesticide Information Center, “Pure dicamba is low in toxicity if breathed.” Additionally, the website states that “Following dicamba's uptake, the chemical is rapidly eliminated in the urine, mostly unchanged.”

The Heartland Study seeks to understand if that is in fact true. In one of the largest and most sophisticated birth cohort studies on herbicides ever conducted, the group plans to enroll thousands of expectant mothers and record the outcomes of their pregnancies. The group will follow the children through age three to assess growth

and developmental issues and hopes to continue following the kids through age 16.

Recent studies have already linked issues like shortened pregnancies to exposure to herbicides. One study also found that higher concentrations of glyphosate in the urine of pregnant women were related to increased visits to the neonatal intensive care unit for their infants. And a study of almost 50,000 pesticide applicators in Iowa and North Carolina found an increased risk of liver and intrahepatic bile duct cancer for those who sprayed dicamba.

The use of dicamba has risen more quickly than any herbicide in the world, and in many cases, Benbrook explained, women in the general populace have never been exposed to it at the levels they now are. In 2022, 95 percent of all soybean crops were genetically modified to resist weeds as were 90 percent of corn plants, most of which used glyphosate and/or dicamba.

But perhaps most ambitiously, the HHRA study seeks to record the levels of 7 different types of herbicides in pregnant women and aims to assess the impact of such a high toxicity load on those living in both rural and urban communities in the Midwest.

“We know that the average person in the Midwest—not just pregnant women but men and boys, grandpas and grandmas—is exposed daily to at least seven different pesticides, mostly through their food,” Benbrook told me. “That is a significant chemical load.”

What that chemical load means for the human body, and for children in utero, is what the Heartland Study aims to find out.

“Seeking insights on which herbicides are causing problems is like peeling away layers of an onion to get at the "truth" at its core,” Benbrook told me. “We will face many hurdles in getting to the core, but have the best chance of any ongoing project.”