Domestic phosphate reserves have been estimated to contain more than 600 000 tons of uranium at an average U3O8 concentration of ∼0.015%. Research in the 1940s showed that this uranium could be extracted as a by-product of wet-process phosphoric acid production, but the low price of uranium at that time prevented the formation of a viable industry. Research on process improvement was continued by Oak Ridge National Laboratory and by the Bureau of Mines during the 1960s and 1970s, and in 1974 and 1975, the increase in the price of uranium caused many phosphate producers to reexamine uranium recovery. Several companies entered the business, and by 1981, commercial plants will be recovering about 4.5 million pounds of U3O8 per year. Uranium extraction from phosphoric acid is an example of natural resource conservation: if the uranium is not extracted, it is forever lost from the economy. A side benefit is that the concentrations of radioactivity in fertilizers are lowered significantly.