Updated on September 10th, 2025
Atrazine herbicide—one of the most heavily applied weed killers in U.S. agriculture—has long been at the center of environmental and health debates. While pesticides are designed to protect crops, their influence often extends beyond fields—impacting biodiversity, contaminating water and posing risks to human health.
Atrazine isn't just a farm chemical—it's one of the "most commonly reported contaminants in groundwater and public drinking water" — U.S. Right to Know
In 2009, The New York Times reported that 33 million Americans had atrazine in their tap water. And the Natural Resources Defense Council (NRDC) found it in every watershed monitored by the Environmental Protection Agency (EPA).
Atrazine weed killer: Widespread use in U.S. agriculture
Atrazine weed killer—sold under labels like Atrazine 4L or in atrazine granules—is the second-most widely used herbicide in the U.S., according to the EPA's pesticide sales data.
The U.S. Geological Survey (USGS) estimates that more than 70 million pounds are applied each year. Farmers rely on it heavily for crops like corn, soybeans and sugarcane. USDA estimates confirm this dominance, with atrazine treatment on more than 65% of U.S. corn acreage.
Atrazine use is especially concentrated in the Midwest, where corn production is highest. The NRDC has documented particularly high levels of contamination in Iowa, Illinois, Indiana, Minnesota, Nebraska and Ohio—a theme explored further in later sections.
And it’s not just farms: atrazine also appears in turf treatments, golf courses and residential lawns. Do you know if it’s being used on yours?
Is atrazine in tap water? Understanding groundwater contamination
Many people ask: is atrazine in tap water? The answer—backed by years of monitoring and noted above—is yes.
According to the USGS, atrazine is among the most frequently detected herbicides in domestic water wells. The EPA has also listed it as one of the most common contaminants in U.S. drinking water systems. Even The Seattle Times has reported that atrazine is consistently detected in tap water across multiple states.
The problem has led to lawsuits: at least 43 water systems in Illinois, Indiana, Iowa, Kansas, Mississippi and Ohio have sued atrazine’s manufacturers to recover the high costs of removing it from public drinking water.
But why is this important to you? Because what flows into our water systems eventually makes its way into our bodies. And the effects of atrazine on humans are serious, particularly when it comes to hormones and reproductive health.
Effects of atrazine on humans: Endocrine and reproductive risks
Atrazine’s most concerning effects on humans come from its role as an endocrine disruptor. According to the EPA, the endocrine system regulates critical processes from conception through adulthood, including brain development, reproductive function, metabolism and blood sugar control. Even at levels regulators consider “safe,” atrazine exposure has been linked to widespread risks.
- Thyroid disruption and metabolism impacts: Research shows atrazine interferes with the hypothalamic-pituitary-gonadal (HPG) axis, altering thyroid hormone levels. These changes can slow metabolism, disrupt energy balance and impair both physical and cognitive development.
- Intrauterine growth retardation (IUGR): Babies exposed in the womb may grow more slowly than expected, increasing risks of developmental delays and chronic conditions such as diabetes and heart disease.
- Small-for-gestational-age (SGA) births: Infants born significantly underweight for their gestational age face higher risks of lifelong health issues, including cardiovascular disease and impaired glucose tolerance.
- Spontaneous abortion: Studies show higher rates of miscarriage among women in agricultural regions with elevated atrazine exposure.
- Gastroschisis: A 2023 study in JAMA Network Open linked county-level atrazine exposure to higher rates of this severe birth defect, where an infant’s intestines develop outside the body through a hole near the belly button.
- Reduced semen quality: Male fertility may be affected through lower sperm counts and impaired motility.
- Menstrual irregularities: Exposure has been linked to cycle disruptions, including abnormal bleeding and inconsistent durations.
These findings highlight that the effects of atrazine on humans go well beyond agriculture—affecting thyroid health, metabolism, reproductive function and long-term generational outcomes.
Case insight: Atrazine's impact on reproductive health
Research published in Environmental Research compared atrazine exposure in Illinois and Vermont. In Illinois—where atrazine is heavily used—concentrations in drinking water were nearly twice as high as in Vermont, even though both remained within EPA legal limits.
- Women in agricultural areas in Illinois were up to five times more likely to experience irregular menstrual cycles.
- These women reported lower estrogen levels, suggesting atrazine disrupted normal hormone function.
- The study concluded that even "legal" levels of atrazine exposure could affect reproductive health.
This case highlights why atrazine’s risks are so concerning: they may persist even when contamination meets EPA guidelines.
Beyond humans: Atrazine's toll on aquatic and animal life
Atrazine’s impact isn’t limited to humans—its reach extends to aquatic and wildlife populations.
- Hormonal disruption: Laboratory research shows that even minimal atrazine levels can act as an endocrine disruptor, affecting hormone systems in fish and amphibians
- Developmental and reproductive effects: Fish and frogs exposed to atrazine experience reproductive abnormalities, delayed development and changes in hormone regulation.
- Fertility impacts in aquatic life: Studies on frogs and fish report reduced spawning, lower egg production and genetic changes.
- Feminization of male frogs: UC Berkeley studies reveal that male frogs exposed to just 2.5 parts per billion can develop functional female reproductive organs, capable of laying viable eggs—dramatically altering local populations.
Exposure to atrazine at levels accepted by the Environmental Protection Agency can turn male frogs into females that reproduce. — UC Berkeley, 2010
Concluding reflections: Atrazine's global influence on health and environment
The debate over atrazine herbicide highlights the tension between its agricultural benefits and the mounting risks to human health and ecosystems. Research continues to reveal troubling side effects of atrazine—from endocrine disruption and reproductive harm to biodiversity loss in aquatic environments.
While atrazine has been banned in Europe for more than two decades, it remains widely used in the United States, raising questions about long-term safety.
Scientific evidence suggests there is no need to continue its use, especially with safer alternatives available for pest management. We at Dr. Killigan’s stand by this approach, advocating for effective, environmentally responsible solutions.
As evidence grows, so does the responsibility to stay informed. Understanding the risks of atrazine is the first step toward advocating for safer practices, healthier communities and greater accountability in how pesticides are regulated and applied.
