Nine low-income families in Baltimore row houses agreed to let researchers till the sewage sludge into their yards and plant new grass. In exchange, they were given food coupons as well as the free lawns as part of a study published in 2005 and funded by the Department of Housing and Urban Development...
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.