You may be tossing back weed-killer with your drinking water, especially if you live in the Midwest. According to a new report, pesticides contaminate tap water supplies in dozens of American cities during the growing season, when levels frequently can exceed federal standards.

The survey, conducted by the Environmental Working Group, focused mainly on the Midwest from May to August, when herbicide use is highest. And to the dismay of Corn Belt residents, it showed drinking water laced with a variety of chemicals -- some that have been shown to cause birth defects, reproductive disorders, and even cancer in lab animals.

"We know that these chemicals are toxic. And we know that they're exceeding the levels the government has set for these chemicals in water," said Richard Wiles of the Environmental Working Group. "We've got cities where the water contamination is at levels in excess of federal health standards for weeks and months at a time."

Of 29 cities sampled, the only one to come out clean was Memphis, Tennessee, which uses deep wells for its drinking water. The biggest offenders: New Orleans, where farm runoff arrives via the Mississippi River; Omaha, Nebraska; Indianapolis and Fort Wayne, Indiana; Danville, Decatur, Granite City and Springfield, Illinois; Columbus and Bowling Green, Ohio; Kansas City, Kansas; and Jefferson City, Missouri.

Also surveyed: Topeka, Johnson County, and Lawrence, Kansas; Iowa City, Cedar Rapids, Des Moines, and Davenport, Iowa; Kansas City and St. Louis, Missouri; Richmond and Muncie, Indiana; Alliance and Akron, Ohio; and St. Paul, Minnesota.

Concentrations of the chemicals atrazine and cyanazine were especially high in Danville and Decatur, Illinois; Columbus, Ohio; Indianapolis and Fort Wayne, Indiana; and Kansas City, Kansas. The report suggests parents in those cities make sure their kids drink water from alternate sources, such as bottled water, from May through August.

An official from the EPA said the findings were "consistent with what we know is out there." However, she pointed out that the EPA's standards track a yearly average, and this report skews toward an especially heavy pesticide-use period. The EPA, she stressed, worries about the long-term cumulative effects of ingesting the chemicals.

"We believe that for systems that meet federal standards, the water is safe to drink," she said, although she acknowledged that some of the cities surveyed had failed compliance tests in the past.

One of the study's authors, Brian Cohen, disagrees with the notion of "long-term harm." "If you're a mom and you conceive a child on May 15 in Danville and someone tells you it's OK because in January you won't be exposed at all, I'm not sure most people would accept that as a responsible approach," he said.

For their part, farm chemical industry representatives call the report alarmist. A written statement from the American Crop Protection Association says, "Safety standards for drinking water are extremely strict. Drinking water for Americans of all ages is safe." That's a point the drinking water industry itself echoes. "The bulk of the drinking water in the U.S. is absolutely safe to drink," said John H. Sullivan of the American Drinking Water Association. "What this report does is highlight some of the issues we should be concerned about."

Source: CNN - August 17, 1995 -From Environmental Correspondent Sharon Collins