EAST ST. LOUIS, Ill. — Miami County Rural Water District 2 and the city of Carbondale have joined a group of public water systems in the Corn Belt that have filed a federal class-action lawsuit against the maker of the farm herbicide atrazine. The suit was filed in the U.S. District Court of the southern Illinois district based in East St. Louis. The group is seeking at $5 million from Syngenta Crop Protection and the Swiss company Syngenta AG to cover their expenses in treating water contaminated with atrazine. In its court filing, the group says that because of its chemical composition, atrazine runs off into water supplies easily and poses a risk to human health. The group also said that Syngenta has hidden scientific data on atrazine’s potential of human harm. The group noted that the European Union bans the use of atrazine. The Kansas Grains Commission’s Sue Schulte said corn, soybean and milo farmers depend on atrazine to control weeds in their fields. U.S. Environmental Protection Agency research shows that atrazine levels in untreated Carbondale and Miami County water sources are well below federal safe drinking water levels, she said.