The Missouri Department of Natural Resources has found pesticides in almost half of the state's public surface water supplies, and regulators say 10 of those supplies violate federal drinking water laws.
According to a study released this week, 49 of 102 public surface water supplies contained pesticides including atrazine, the most commonly used weed killer.
Traces were found in St. Louis and St. Louis County water supplies from the Mississippi and Missouri rivers, but these traces did not violate the law, said Terry Timmons, a drinking water specialist for the department. "The concentrations in St. Louis and St. Louis County were way below the standards," he said.
All of the 10 locations where violations were found were in northern and northwestern Missouri, Timmons said.
Federal regulations require that the public drinking supplies comply with the pesticide limits by May or face potential penalties.
The surface water supplies collect water from streams, rivers and lakes, Timmons said. Most of the approximately 2,000 water supply systems in Missouri draw their supplies from ground water, Timmons said.
State regulators assembled many water suppliers on Thursday at a hotel in Chillicothe and cautioned them that they must comply.
But some suppliers scoffed at the high cost of compliance, while others questioned the limited data on the health effects of atrazine.
"We have nothing to tell our customers," said Bob Surber, who supervises Harrisonville's water system. "There's nothing to back this up, and it probably won't hold up in court."
Atrazine causes mammary tumors in rats, prompting concern that it may cause cancer in humans. In Missouri, 3.8 million pounds of atrazine …