A five-month probe by Jeff Donn, Martha Mendoza and Justin Pritchard, of the Associated Press, found traces of medications in the drinking water supplies of over 40 million Americans. While the testing found pharmaceuticals diluted to miniscule concentration levels, some scientists question the long-term effects of sustained exposure. The AP reports: "The situation is undoubtedly worse than suggested by the positive test results in the major population centers documented by the AP. The federal government doesn't require any testing and hasn't set safety limits for drugs in water. Of the 62 major water providers contacted, the drinking water for only 28 was tested."