An estimated 8 billion pounds of sewage sludge are routinely spread onto farmland in the USA each year. In 2001 researchers reported finding high concentrations of Polybromodiphenyl ethers (PBDEs) in 11 samples of sewage sludge from Virginia, New York and California. (Sewage sludge in the US contains 10 to 100 times as much PBDE as does European sludge.) The US EPA had employed risk assessment to declare the use of contaminated sewage sludge "safe" as fertilizer on food crops. However it did not consider the effects of PBDEs (or many other chemicals) on the crops, on people eating the crops, or on the natural environment in which the crops are grown.