Edited sentence: Barium is present at the rate of 500 mg/kg, while manganese is present at the rate of 1 g/kg sludge.High levels of sterols and other hormones have been detected, with averages in the range of up to 1,000,000 µg/kg sludge.It is unknown whether mineral speculators have yet invested in the sludge stocks of the United States.Lead, arsenic, chromium, and cadmium are estimated by the EPA to be present in detectable quantities in 100% of national sewage sludges in the US, while thallium is only estimated to be present in 94.1% of sludges.Silver is present to the degree of 20 mg/kg of sludge, on average, a near economically recoverable level, while some sludges of exceptionally high quality have up to 200 milligrams of silver per kilogram of sludge; one outlier demonstrated a silver lode of 800-900 mg per kg of sludge.Some highlights include:.The EPA has recently (as of 2009) released the Targeted National Sewage Sludge Study, which reports on the level of metals, chemicals, hormones, and other materials present in a statistical sample of sewage sludges