According to the Natural Resources Defense Council, a common herbicide atrazine has been found at three times the recommended level for safety.

From the Iowa Independent Article:

The study included data from two Iowa watersheds — the Nishnabotna River in western Iowa, where 82 percent of samples taken contained atrazine, and Wolf Creek in Black Hawk and Grundy counties where 96 percent of samples taken contained atrazine. In Wolf Creek samples, the maximum peak atrazine concentration was 10 parts per billion (ppb), more than three times the EPA standard atrazine level for drinking water.

The study also looked at 12 public water systems in southern Iowa. The highest concentration of atrazine in raw water was found at the Winterset Water Treatment Plant in Madison County, where the maximum concentration was 47.5 ppb. This system serves approximately 4,768 people and uses water from Cedar Lake.

Atrazine has been shown to cause problems with the development of reproductive organs.  Exposure to this chemical in your local Iowa tap water is preventable.  Your local Iowa Culligan Dealer can help you put together a package to help filter your water and keep you safe from contaminants.