Widely Used Herbicide Found in Quarter of US Rivers

A harmful weed killer called atrazine contaminates nearly 25% of all continental US rivers at levels that can hurt wildlife and pose risks to human health. A new study of federal records shows the affected waterways cover about 860,000 miles.

Water and Health Risks

The polluted rivers touch over 20% of surface drinking water intakes across the country alongside more than 675,000 private and commercial wells. Atrazine alters hormones and chemical systems in humans and animals, particularly impacting developing children and fetuses. Research links the chemical to impaired fetal growth, birth defects, pre-term birth, low birth weight, irregular menstrual cycles, and lower sperm counts. It also damages animal livers, kidneys, and hearts, while turning male frogs to females and chemically castrating them.

Sources and Scale

The chemical is the second most widely used pesticide in the US, with about 70 million pounds sprayed on crops every year. It mostly targets commodity crops like corn, sugarcane, and sorghum. The International Agency for Cancer Research classifies atrazine as a probable carcinogen. The Center for Biological Diversity compiled the report by analyzing EPA records, marking the first time anyone has mapped the full scope of the threat. Nathan Donley, an environmental health science director at the center, stated that the EPA has failed to act for decades. Five major contamination hotspots include the midwest corn belt, the Chesapeake Bay region, the lower Mississippi River, Florida's Lake Okeechobee, and the Texas Gulf coast. In the midwest corn belt, more than two-thirds of river miles are contaminated, affecting half the regional wells and 68% of drinking-water treatment intakes. Tyrone Hayes, a researcher at the University of California, Berkeley, noted that the chemical travels through the atmosphere, meaning atrazine sprayed in Kansas can rain down on Minnesota.

Legal Action and Industry

Atrazine is banned in 60 countries, including the European Union, since 2003. Litigation in the US aims to strike down its approval, and public health groups have sued the EPA over the chemical. Analysts estimate US sales for the product will reach $2 billion to $3 billion in 2025. The EPA and chemical giant Syngenta did not immediately respond to requests for comment.

Context

Atrazine is an agricultural chemical primarily used on large-scale commodity crops to control broadleaf weeds. Because it dissolves easily in water and travels through the air, agricultural runoff frequently carries it far from where it was originally sprayed into public waterways and groundwater supplies.