What is the problem?

Rising glyphosate use has led to rising levels in humans. The Heartland Study is designed to find out if moms and babies are paying the price of pesticide use.

Weeds impact every farm field, every year, everywhere around the world.

Herbicides are pesticides that control weeds and they account for over two-thirds of global pesticide use. Herbicides are the only type of pesticide for which use is rising, with no end in sight.

How did we get here?

The widespread planting over the last 20 years of corn, soybean, and cotton seeds genetically engineered to resist glyphosate herbicide (aka Roundup) brought about a revolution in weed management system technology.

The simplicity and effectiveness of so-called “Roundup Ready” seeds led to rapid, near universal adoption by 2000, but also set the stage for the emergence and spread of weeds first tolerant of, and eventually resistant to glyphosate.

Resistant weeds are the fuel pushing the herbicide treadmill into ever-higher gears. Today, there are over two-dozen types of weeds that have developed resistant to glyphosate. Most glyphosate-resistant weeds are also resistant to one to three other classes of herbicides, and a few weeds are resistant to nearly all currently registered herbicides.

Corn and soybeans are the crops contributing most significantly to rising herbicide use in the Midwest.

Conventional farmers in the Midwest are locked in a resistant weed vs. herbicide arms race. On many large-scale, corn-soybean farms in the Midwest, weed-management-system collapse is perilously close, and yet the seed-biotech-pesticide industry’s response has been to develop and market new GMO seeds resistant to multiple, and now higher-risk herbicides.

In just the last few years by various measures, the use of these herbicides has nearly — or more than — doubled in Midwestern corn and soybean production. Farmers are spraying four to five different herbicides on many fields that required only one or two herbicides just a few years ago.

More herbicide applications are needed to bring a crop to harvest. Markedly more total pounds of herbicide active ingredient are sprayed on millions of crop acres. Further and substantial increases are inevitable because of new-generation GMO seeds engineered to resist glyphosate, plus dicamba or 2,4-D, as well as 6 or more other herbicides.


Close to 90% of the soybean seed sold to US farmers for the 2019 production season is genetically engineered to withstand applications of either glyphosate and dicamba, or glyphosate and 2,4-D. Multiple-herbicide-resistant corn hybrids will reach the market by 2020. At no time in U.S. history has a region of the country experienced an increase in the spraying of high-risk herbicides comparable to what is now unfolding in the Midwest.

“At no time in U.S. history has a region of the country experienced an increase in the spraying of high-risk herbicides comparable to what is now unfolding in the Midwest.”  — Dr. Charles Benbrook, Science Team Member


Farmers Still Struggling

Despite spraying more herbicides more often, farmers are still struggling to keep up with the spread of resistant weeds.

Corn and soybean weed management costs have been driven upward incrementally for almost 25 years by the ever-higher premiums charged for herbicide-resistant GMO seeds, plus the cost of the herbicides needed to keep ahead of weeds. Overall,  weed management costs have about tripled since the mid-1990s, taking a sizable bite out of what was once net farm income.

Public Health Costs = Unknown

While weed management problems on the farm are widely recognized and a cause of deep concern, the public health consequences of rising herbicide use have received scant attention.

Rising herbicide use inevitably leads to new routes of exposure, and for some people, higher overall levels of exposure.

Are the dramatic changes in herbicide use unfolding across the Midwest triggering changes in the frequency and/or severity of reproductive problems, birth defects, and other adverse birth outcomes? The Heartland Study’s research protocol is designed to detect any such changes, if they are in fact occurring.

We seek to determine whether herbicides are making it harder for women to have normal pregnancies, or to give birth to healthy babies with their full cognitive potential.  The Heartland Study will also investigate, for the first time in the human population, a possibility that keeps scientists up at night – are prenatal pesticide exposures causing epigenetic changes that can alter gene expression, and thus the frequency of chronic disease and neurological impairment across multiple generations?

Our Core Hypothesis:

Is rising herbicide exposure leading to reproductive problems, adverse birth outcomes or developmental delays in America's Heartland?


While our Project Bibliography includes research on a wide range of herbicide health impacts, the initial focus of our work is on how exposure to these chemicals impacts conception, pregnancy, birth, and early childhood development.

Why Moms and Babies?

We have chosen to focus on adverse reproductive and birth outcomes for three reasons.

First, it is widely accepted that pregnant women, developing fetuses, and infants and children through age 16, are at substantially heightened risk compared to the rest of the population following even very low levels of exposure to chemicals, including pesticides. In fact, just one day before this website went online, the International Federation of Gynecology and Obstetrics released a statement calling for a “full global phase out” of glyphosate due to concerns about health impacts to women and children.

Second, the time period during which reproductive problems, developmental delays, and birth defects are observable is relatively short (a few years), compared to, for example, cancer, neurological disease, or renal failure, adverse impacts that generally take 10 to 25 years to occur, and even longer to trace back to specific exposures and chemicals.

The third reason is more speculative, but more chilling in terms of public health and societal impacts. In the last five years, several animal studies have reported the capacity of relatively low-level exposures to pesticides during the early stages of pregnancy to trigger heritable, epigenetic changes in DNA expression patterns in the offspring.

Such epigenetic changes can predispose future generations to adverse developmental or chronic health problems. Adverse impacts previously reported range from abnormal sexual development and impaired sperm health, to reduced IQ and behavioral problems, and certain cancers (especially of the reproductive system).

The two most widely used herbicides in the Midwest (and world) — glyphosate and atrazine — have both been shown to trigger heritable, epigenetic changes in DNA in animal studies. Glyphosate has been classified by the International Agency for Research on Cancer (IARC) as a probable human carcinogen. Use of the two herbicides linked to newly approved GMO seeds — 2,4-D and dicamba — is rapidly rising in the Midwest. Both are known to be linked to reproductive problems, birth defects, and elevated risk of certain cancers.

Given the now ubiquitous exposures to these four high-risk herbicides in the Midwest, it is critical to determine whether prenatal herbicide exposures in humans might also trigger heritable, epigenetic changes in newborns. The Heartland Study will strive to do so by combining cutting-edge genomic science with rigorous clinical tracking of pregnancy and birth outcomes.


Study Design

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