What have been the trends in the levels of atrazine in water supplies?

During the 1980s, atrazine was frequently detected in groundwater and especially in surface water in Midwestern, Western, and Eastern states and in Florida.

Levels of atrazine frequently exceeded the Maximum Contaminant Level (MCL) of 3 micrograms per liter allowed in public water supplies. This level is set by the Environmental Protection Agency. It is the highest level of a contaminant allowed in public drinking water.

Levels of atrazine detected often exceeded 20 micrograms per liter. The Environmental Protection Agency, in their most recent risk assessment for atrazine, stated that the greatest concern in water supplies for human or ecological health is when concentrations were 10 to 20 micrograms per liter or greater.