Chloride is a chemical element found in salts, which tend to dissolve easily in water. In natural waters, elevated levels of chloride may indicate inputs of human or animal waste, or inputs from fertilizers, many of which contain salts. During winter months, elevated chloride levels in streams may occur as a result of road salt runoff to nearby streams. The amount of chloride dissolved in water is expressed in milligrams per liter of water (mg/L). Average chloride concentrations for Iowa streams range from 16 to 29 mg/L. The Iowa DNR released, Water Quality Standards Review: Chloride, Sulfate and Total Dissolved Solids a study examining the effects of sulfate and chloride on aquatic ecosystems in Iowa.