Atrazine is a chlorinated herbicide of the triazine class, widely used globally to control broadleaf and grassy weeds in major crops like corn, sorghum, and sugarcane. It acts both before and after plant emergence. The chemical is known for its environmental persistence, with a half-life in soil ranging from a few months to over a year, depending on local conditions. Once applied, Atrazine can migrate from agricultural fields, posing a potential health concern for humans.
Sources of Human Exposure
The general public’s most frequent route of exposure is through contaminated drinking water, especially for those living in agricultural regions where the herbicide is heavily used. Due to its solubility and resistance to degradation, Atrazine readily enters surface water through runoff and can also leach into groundwater supplies. Concentrations in community water systems can fluctuate, sometimes spiking during the application seasons in the spring and summer months.
Occupational populations, such as farm workers, herbicide applicators, and manufacturing employees, face a separate, higher level of exposure. These individuals are exposed through dermal contact, inhalation of spray or dust, and accidental ingestion. Exposure for the general population via residues on food crops is typically low, and the chemical does not tend to build up significantly within the human body.
Endocrine Disruption Mechanism
Atrazine is classified as an endocrine-disrupting chemical because it interferes with the body’s natural hormonal signaling pathways. The primary mechanism involves disruption of the hypothalamic-pituitary-gonadal (HPG) axis, the complex system that controls reproductive and hormonal functions. Atrazine and its metabolites can alter the balance of hormones produced by this axis, even at low concentrations. A specific action of the herbicide is increasing the activity of the aromatase enzyme. Aromatase converts androgens, such as testosterone, into estrogens. This increased conversion reduces male hormones and elevates female hormones, which can lead to adverse effects on reproductive health.
Documented Health Outcomes
Research into human populations exposed to Atrazine focuses heavily on reproductive and developmental effects. Epidemiological studies indicate associations between exposure during pregnancy and adverse birth outcomes, including low birth weight and intrauterine growth retardation. Some research also suggests a possible link between maternal exposure and an increased risk of specific birth defects, such as cardiac, urinary, and limb defects, as well as preterm delivery.
For adult reproductive health, exposure has been correlated with changes in menstrual cycles and decreased fertility in women. In men, studies suggest a correlation between Atrazine exposure and reduced sperm quality.
Regarding cancer risk, the evidence remains mixed and inconclusive across human studies. However, the World Health Organization’s International Agency for Research on Cancer (IARC) has classified Atrazine as “probably carcinogenic to humans” based on sufficient evidence from animal studies and mechanistic data. Human epidemiological studies have noted potential links to certain cancers, including ovarian, breast, and prostate cancer, especially in highly exposed occupational groups.
Regulatory Oversight and Safety Limits
In the United States, Atrazine is regulated by the Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Safe Drinking Water Act. The EPA has established a Maximum Contaminant Level (MCL) for Atrazine in public drinking water at 3 parts per billion (ppb), or 3 micrograms per liter. This standard is intended to protect the public from chronic exposure effects. The EPA also requires ongoing monitoring of water sources in high-use areas to ensure compliance with the safety limits. In contrast, the European Union implemented a complete ban on Atrazine use in 2004. This decision was based on findings that the herbicide frequently exceeded regulatory limits for pesticides in groundwater, which the EU sets at a very low precautionary standard.