Things like contaminants, as they build their way up through the system, it???s eagles that end up with the lethal dose of it.BILL MOYERS: Along with trace amounts of DDT, mercury, lead and other chemicals in the birds??? blood, the biologists have found elevated levels of PCBs.PETER NYE: Easy, got it.BILL MOYERS: They???re watching closely to determine what effect these chemicals will have on the