| Thomas A. Burke, professor at The Johns Hopkins School of Public Health in Baltimore, Md., Thursday, July 19, 2007. The idea that sludge, the leftover semisolid wastes filtered from water pollution at 16,500 treatment plants, can be turned into something harmless, even if swallowed, has been a tenet of federal policy for three decades. A series of reports by the EPA's inspector general and the National Academy of Sciences between 1996 and 2002 faulted the adequacy of the science behind the EPA's 1993 regulations on sludge. The chairman of the 2002 academy panel, Thomas Burke, a professor at the Johns Hopkins Bloomberg School of Public Health, says epidemiological studies have never been done to show whether spreading sludge on land is safe.(AP Photo/Kathleen Lange |