mating exposures of individual participants in the epidemiologic study of Colorado uranium miners are described in National Institute for Occupational Safety and Health-National Institute for Environmental Sciences Joint Monograph No. 1 (Lundin and others 1971). A 1968 report of the Federal Radiation Council addressed the accuracy of the exposure estimates. SENES Consultants Limited of Ontario, Canada, has prepared a report entitled "Preliminary feasibility study into the re-evaluation of exposure data for the Colorado Plateau uranium miner cohort study" (SENES 1995). This report provides an extensive description of the calculation of the WLM values for the epidemiologic study and gives insights into the sources of variability and error in the estimates.

The following description is taken largely from the 1971 monograph authored by Lundin and colleagues. The U.S. Public Health Service began surveying for radon in uranium mines in 1949. In 1950 they were joined by the Colorado State Department of Health and in 1951 by the U.S. Bureau of Mines for mines on Indian reservations. Coverage was far from complete; 1949 "a few measurements," 1950 "relatively few mines," 1951 "but again coverage was incomplete," (Lundin and others 1971). By 1952 an effort was made to survey all operating mines and radon progeny were sampled in 157 mines. This sampling may have examined most of the larger mines, but government records