"USA Sludge Researchers from Cornell University and the American Civil Engineers have found more than 60,000 toxic substances and chemical compounds in US sewage sludge, and report that 700 to 1000 new substances are developed every year, some of which also enter the sewage stream. These substances include PCBs, pesticides, dioxins, heavy metals, asbestos, petroleum products, and industrial solvents, many of which are linked to ailments ranging from cancer to reproductive abnormalities. They are also a threat to soils: once introduced to cropland, for example, heavy metals persist for decades (as in the case of cadmium) or even centuries (as in the case of lead)."