ATTACHMENT 2 REPORT NO. 8 REVISED GUIDANCE FOR THE CONTROL OF RADIATION HAZARDS IN URANIUM MINING SEPTEMBER 1967 Staff Report of the FEDERAL RADIATION COUNCIL RECEIVED U.S. DEPARTMENT OF ENERGY DEC 10 1986 LIBRARY WASHINGTON, D.C. 20545 launched new major mining industry. Thereafter employment in uranium mines increased rapidly until 1961, when it declined as a consequence of curtailed Government purchases. Open it mining of uranium did not become significant until 1955. The number of uranium mines providing ore during the years 1954 through 1966 and the corresponding employment figures are show in tables 1 and 2, respectively. Table 1.--Estimates of the number of mines producing uranium are during the calendar year as reported by the industry to the U.S. Bureau of Mines (1954-64) and AEC (1965-66) FOR REFERENCE SEE (14bb03.gif) 4 TABLE 4.--Estimated distribution of mines by Working Level ranges from 1956 through 1959. Year Number of <1.0 WL 1.0-2.9 WL mines % % measured 1956 108 19 25 1957 158 20 26 1958 53 28 21 1959 237 18 26 3.0-10.0 >10 WL % Total WL % 33 23 100 28 26 100 36 15 100 28 28 100 2.10 This breakdown suggests that about one-fourth of the work force was probably exposed to atmospheres leading to annual exposures larger than 10 WL. and about one-fifth was exposed at average levels lower than 1 WL. It is also noteworthy that the number of mines surveyed between 1956 and 1959 was but a small fraction of the total uranium mines. This low coverage was due to the common event that many small mines were not in operation at the time of the survey. Many such mines were located in remote areas and operated only a few weeks or months in each year because of such factors as available ore, operating funds, labor supply, weather, and so forth. 2.11 In December 1960 a Governors' conference on health hazards in uranium mines6 was held in Denver, Colo. This was an out growth of interagency studies on the occupational health problems of uranium miners carried out by the Public Health Service, the Atomic Energy Commission, the U.S. Bureau of Mines, and the Department of Labor. The objectives of the conference were to present to the Governors of States engaged in uranium mining, data on the prevailing radon daughter levels, such as these indicated in table 4, to present information on experience in controlling radiation hazards; and to assist in developing cooperative programs to reduce radiation hazards in uranium mines. As a result of this conference, many of the States placed more emphasis on their mine inspection programs. 2.12 As a measure of the prevailing levels of radon daughters in the mines, table 5 indicates the results of samples taken in the third calendar quarter of 1965 and 1966. These data indicate considerable success in reducing concentrations of radon daughters. The mine operating companies are cooperating with State regulatory agencies to improve control of radon daughter concentrations in working areas of the mines. The possibility of further reduction in the mines reporting average WL values between 1 and 10 involves considerations discussed in section IV. 2.13 The significance of these recorded data is limited by several considerations: (1) individual WL measurements usually represent a 10-minute sample at a selected location; (2) a number of samples taken per survey is restricted by the number of survey personnel that can be accommodated in an operating mine and by the manhours available to collect and analyze the individual samples; and (3) the frequency of surveys in individual mines varied widely; a single survey per year was common practice in some states, while in others surveys were even less frequent. 2.14 The U.S. Bureau of Mines carried out a study in 1962 on a modification of the usual practice in selecting locations to be sampled in a mine. The report on this project7 indicates that an estimate of the time-weighted assessment of miner occupancy in spot- 12 Table 5.--Summary of radon daughter concentrations by Working Level ranges during the third quarter of 1965 and 1966. __________________________________________________________________ 1965 __________________________________________________________________ State Number <1.0 Percent of mines in each WL range mines ---------------------------------- 1.0-29 3.0-4.9 5.0-10.0 >10.0 __________________________________________________________________ Arizona 16 50 19 12 19 Colorado 124 39 42 12 6 1 New Mexico 26 15 38 42 5 Utah 47 49 43 4 4 Wyoming 16 44 56 ...... ..... ______________________________________________________ Total 229 39 41 13 6 1 ______________________________________________________ 1966 __________________________________________________________________ State Number <1.0 Percent of mines in each WL range mines ---------------------------------- 1.0-29 3.0-4.9 5.0-10.0 >10.0 __________________________________________________________________ Arizona 14 57 29 14 Colorado 148 45 42 7 5 1 New Mexico 23 17 47 30 6 Utah 33 55 39 ..... 6 Wyoming 13 38 54 8 .... _______________________________________________________ Total 231 44 42 9 4 1 _______________________________________________________ sampled areas permits an approximate evaluation of the exposure of individuals for the day of sampling. The report indicates that as few as four area samples may be sufficient to evaluate the exposure of an individual with a probable accuracy of plus/minus 25 percent. The examples cited in the Bureau report illustrate the method: (1) a miner working in various areas having concentrations ranging from 3.7 to 8.0 WL had an estimated weighted exposure of 6.1 WL, (2) another miner working in concentrations ranging from 0.3 to 6.4 WL had a weighted exposure of 1.0 WL, and (3) a third one working in concentrations of 0.2 to 1.4 WL had a weighted exposure of 0.5 WL. The results of this study suggest that the arithmetic average of concentrations found in the mine air does not give a reliable estimate of exposure. Similarly, the maximum concentration found in any representative mine sampling bears no direct relation to the exposure of individual miners. 2.15 Time-weighted assessment for evaluating exposures in uranium mines has not been generally adopted for regulatory purposes. Rather, pertinent State regulations and the recommendations of the USA Standards Institute stipulate a maximum concentration that, when exceeded, is used as a basis for closing the mine area concerned. Two of the five States (Colorado and New Mexico), for which data are reported in tables 4 and 5, maintain 13 276-291 0 - 67 - 3 Table 6.--Lung cancer mortality between July 1955 and June 1965 inclusive -- white miners who began underground uranium mining before July 1955 FOR REFERENCE SEE (14bb04.gif) 21 Figure 1. Observed and Expected Annual Lung Cancer Mortality per 10,000 Miners and 95-percent--Confidence Limits in Relation to Exposure* "GIF" FOR REFERENCE SEE (14bb05.gif) 22