Atrazine is one of the most well-studied pesticides because of its extensive use as a weed-killer and the significant risks it poses to human health and the environment. Its chief manufacturer is Syngenta, acquired by ChemChina in 2017.
Atrazine is the second most commonly used pesticide in the U.S., with 65-85 million pounds sprayed each year primarily on corn (see graphs), despite being banned in more than 40 other countries. Atrazine is also used on lawns, school grounds, golf courses, etc., and is often mixed with fertilizers in "weed and feed" products.
Atrazine is water-soluble, relatively mobile, and persistent. Together with its intensive use, these properties explain why it is widely present in U.S. waterways and is detected in water systems serving nearly 30 million Americans.
Atrazine is an endocrine disruptor, which means that it interferes with the hormones that regulate the development and functioning of all our bodily systems. It has been associated with reproductive dysfunction, behavioral abnormalities, and impaired fetal growth. There is also evidence atrazine contributes to birth defects and cancers, including non-Hodkgin lymphoma, breast and prostate cancer.
While of particular concern to farmworkers and their children, atrazine can also be more broadly harmful to human health, especially through exposure from drinking water. Associations have been found between atrazine exposure and low birth weight and small head circumference in newborns.
Atrazine is also extremely harmful to the environment, with impacts to a wide range of plants and animals. Its harmful impacts to amphibians and fish are particularly well documented, with reduced reproductive capacity and reduced chances of survival. Even very low levels of atrazine can impair sexual development in tadpoles, leading to hermaphroditism and demasculinization, and induce chemical castration in adult frogs. Atrazine also impairs fish and amphibian behavior, timing of metamorphosis, and immune function.
In a 2021 Endangered Species Act assessment, EPA itself admitted that atrazine is likely to harm over 1,000 plant and animal species at risk for extinction.
Syngenta engaged in an extraordinary dirty tricks campaign to harass and discredit scientist Tyrone Hayes, whose work first revealed the gender-bending effects of atrazine on amphibians, findings since replicated by many others. Nevertheless, EPA relies almost exclusively on industry-supplied studies, despite independent reviews demonstrating their serious flaws.
In 2016, it appeared the tide might be turning, as EPA concluded in its own risk assessment that atrazine use posed risks to fish, amphibians, invertebrates, mammals, birds, reptiles, and plants across the country. The same year California added atrazine to its list of chemicals known to the state to cause reproductive harm, requiring products containing a certain level of atrazine to include a warning.
However, despite an ever-growing body of evidence of harms from atrazine to human health and the environment, and EPA's own past acknowledgement of these risks, the Trump Administration's EPA nonetheless reauthorized the use of atrazine in 2020. The reauthorization actually weakened key safeguards. For instance, EPA raised the level of atrazine people can be "safely" exposed to based on an exposure model developed by Syngenta, and discontinued a long-standing program for monitoring atrazine levels in community drinking water systems. On the environmental side, EPA exacerbated atrazine's harm to aquatic communities by raising the allowable levels in water from 10 to 15 ppb, nearly 5 times its 2016 proposal to reduce the threshold to 3.4 ppb.
CFS in action
Center for Food Safety (CFS) critiqued EPA's flawed assessments and subsequently initiated a legal challenge. We are continuing to fight EPA's unlawful actions in reapproving the registration of atrazine.