The Associated Press reviewed grant documents obtained under the Freedom of Information Act and interviewed researchers. No one involved with the $446,231 grant for the two-year study would identify the participants, citing privacy concerns. There is no evidence there was any medical follow-up.
Comparable research was conducted by the Agriculture Department and Environmental Protection Agency in a similarly poor, black neighborhood in East St. Louis, Ill. Residents there also were not told of the potential risks.
The researchers said the sludge could help protect the children from brain or nerve damage from lead, a highly toxic element once widely used in gasoline and paint. Other studies have shown brain damage among children, often in poor neighborhoods, who ate lead-based paint that had flaked off their homes.
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.
In a 1978 memo, the EPA said sludge "contains nutrients and organic matter which have considerable benefit for land and crops" despite the presence of "low levels of toxic substances."
But in the late 1990s the government began underwriting studies such as those in Baltimore and East St. Louis using poor neighborhoods as laboratories to make a case that sludge may also directly benefit human health.
The Baltimore study concluded that phosphate and iron in sludge can increase the ability of soil to trap more harmful metals including lead, cadmium, and zinc, causing the combination to pass safely through a child's body if eaten. The results were published in Science of the Total Environment, a research journal, in 2005.
However, there has been a paucity of research into the possible harmful effects of heavy metals, pharmaceuticals, other chemicals, and disease-causing microorganisms often found in sludge.
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, said epidemiological studies have never been done to show whether spreading sludge on land is safe.
"There are potential pathogens and chemicals that are not in the realm of safe," Burke said. "What's needed are more studies on what's going on with the pathogens in sludge - are we actually removing them? The commitment to connecting the dots hasn't been there."
Rufus Chaney, an Agriculture Department research agronomist who co-wrote the Baltimore study, said the researchers gave the Baltimore and East St. Louis families assurances that the Orgro fertilizer was store-bought and safe.
"They were told that their lawn, as it stood, before it was treated, was a lead danger to their children," Chaney said. "So that even if they ate some of the soil, there would not be as much of a risk as there was before. And that's what the science shows."
