Scientists say wastewater spills from oil development in western North Dakota are releasing toxins into soils and waterways, sometimes at levels exceeding federal water quality standards. In a report published Wednesday, Duke University researchers say they detected high levels of lead, ammonium and other contaminants in surface waters affected by recent wastewater spills in the Bakken oilfield region. They also found that soils at spill sites were laced with radium, a radioactive element in brines that form naturally with underground oil and gas deposits. Geochemistry professor Avner Vengosh says long-term monitoring of waters downstream from the spills is needed to determine whether drinking water quality is at risk. North Dakota environmental health chief Dave Glatt says most wastewater spills are cleaned quickly and pose no threat to humans.