Radioactive contamination from the Rocky Flats Plant

The Rocky Flats Plant, a former U.S. nuclear weapons production facility about 15 miles northwest of Denver, Colorado, caused radioactive contamination, primarily plutonium, americium, and uranium, within and outside its boundaries. The facility was dismantled and removed, and the central industrial area of the property became a Superfund site, surrounded by the newly created Rocky Flats National Wildlife Refuge.

The contamination primarily resulted from two major plutonium fires in 1957 and 1969 (plutonium is pyrophoric and shavings can spontaneously combust) and from wind-blown plutonium that leaked from barrels of radioactive waste. Much lower concentrations of radioactive isotopes were released throughout the operational life of the plant from 1952 to 1992, from smaller accidents and from normal operational releases of plutonium particles too small to be filtered. Prevailing winds from the plant swept airborne contamination south and east, into populated areas northwest of Denver.

The contamination of the Denver area by plutonium from the fires and other sources was not publicly reported until the 1970s. According to a 1972 study coauthored by Edward Martell, "In the more densely populated areas of Denver, the Pu contamination level in surface soils is several times fallout", and the plutonium contamination "just east of the Rocky Flats plant ranges up to hundreds of times that from nuclear tests." As noted by Carl Johnson in Ambio, "Exposures of a large population in the Denver area to plutonium and other radionuclides in the exhaust plumes from the plant date back to 1953."

In the 1990s, a series of Historical Public Exposure Studies were conducted to assess past releases and public exposures. For example, the figure at right illustrates the calculated lifetime cancer risk to a laborer from the 1957 Rocky Flats fire. The key shows the cancer risk due to exposure during the 1957 event per million persons. This figure means that an outdoor laborer in the reddest part of Arvada would have roughly a two-in-a-million risk of contracting cancer (0.000002) from being outside during the 1957 fire. The original, complete figure - as well as many others showing the risks of past exposures - can be viewed in the Summary of Findings from the Historical Public Exposure Studies.

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