Sewage sludge, or "Biosolids"
We didn't know that this kind of thing still went on, but scientists spread "biosolids" on yards in poor black neighborhoods in Baltimore to test whether it might protect kids from lead poisoning. The theory was that the iron and phosphates in the sludge would bind to the lead and help it pass through the child's body if eaten.
The parents were told that the stuff was harmless compost, when in fact sludge can be contaminated with heavy metals, pharmaceuticals and microorganisms. Nor were they told that in many parts of the country and in Canada, sludge is not even used on farmland, far away from soil-eating kiddies, because of worries about toxicity.
One environmentalist said choosing poor neighborhoods destined for demolition makes it hard to track a study's participants. "If you wanted to do something very questionable, you would do it in a neighborhood that's not going to be there in a few years." ::Examiner