I reported an increased frequency of small

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1 HISTOLOGIC TYPES OF LUNG CANCER AMONG URANIUM MINERS GENO SACCOMANNO, PHD, MD," VICTOR E. ARCHER, MD,t OSCAR AUERBACH, MD,* MARVIN KUSCHNER, MD,' RICHARD P. SAUNDERS, MD,* AND M. G. KLEIN. MDX A panel of pathologists classified 121 cases of lung cancer from American uranium miners by cell type, and 138 cases of cancer in nonminers. Undifferentiated carcinomas showed a higher incidence with increasing radiation exposure and age and cigarette matched controls. At high radiation exposures, the WHO cell type accounted for more than half the total. An average of.9 years elapsed from the beginning of mining to development of cancer. It was longest among the highly exposed men and was shortest among men with small cell, undifferentiated carcinoma who had less than 700 Work Level Months exposure. In all age and cigarette groups, radiation exposure increased the small cell, undifferentiated, but decreased the epidermoid tumors. Age showed an increase in epidermoid carcinoma. Undifferentiated small cell types were slightly increased among the lowest exposure groups. These increases and an excess of these cell types among South African gold miners seem to establish a trend. N A PREVIOUS REPORT, SACCOMANNO ET AL.13 I reported an increased frequency of small cell undifferentiated carcinoma among the bronchogenic carcinomas of American uranium miners. Concomitant epidemiologic studies had established that lung cancer was unusually frequent among uranium miners, and that the excessive lung cancer was most probably due to radiation exposure.7110 These studies also showed that as the radiation exposure increased, there was an accompanying increase in the incidence of lung cancer.ls7 At the time of the Saccomanno report,l3 only 51 lung cancers among uranium miners were available for analysis. There are now approximately 0 lung cancers known among uranium miners, Supportcd by Public Health Service Grant PH Pathologists, St. Mary's and Veterans Administration Hospitals, Grand Junction, Colo. t Epidemiologist, Western Area Occu ational Health Laboratory, Bureau of Occupational Sa F ety and Health, Environmental HeaIth Service, Public Health Service, U. S. Department of Health, Education, and Welfare, Salt Lake City, Utah. * Senior Medical Investigator, Veterans Administration Hos ital, East Orange, N. J. S Chief of Pathology, New York University Medical School, New York, N. Y. Address for reprints: G. Saccomanno. MD, St. Mary's Hospital, 7th and Patterson, Grand Junction, Colo. 801.a The authors are grateful for the assistance of Helen B. Miller and Willie L. Turner in this study. ReceiWd for publication August 28,1970. so it was felt that another analysis was warranted, to determine if the small cell undifferentiated carcinomas still predominate, and to explore relationships between cell type, cigarette smoking, age, radiation exposure, and latent period. MATERIALS AND METHODS From an epidemiologic study of uranium miners,lo names and exposure data were available on most men who have mined uranium in the United States. A large proportion of uranium miners seek medical attention in one of the 10 hospitals served by one of the authors (GS). In addition to the pathologic material collected on uranium miners in these hospitals, pathology slides or tissue blocks were generously supplied by a number of other hospitals when, through the epidemiology efforts, uranium miners were found. to have sought medical care for lung cancer in other areas. For control purposes,' tishe' as available from lung cancer cases among males in the above 10 hospitals was used. Tkd population from which these control cases were 'drawn was much larger than the population of uranium miners. All lung cancer cases that had occurred among uranium miners and among 'controls in 'the lu'kiospitals, between Januaty 1949 and July' <i969', were Yeviewed to 5

2 516 CANCER Ma?clz 1971 Vol. 27 see if tissue might be available for inclusion in the study. Of 7 cases reviewed among men who had at some time worked in a uranium mine, 116 were definite lung cancer with a tissue diagnosis, were possible lung cancer, and 26 were cases on which tissue or vital information was not available. All uranium miner cases reported previously13 were included for review here. Of the 21 1 available cases among nonuranium miners reviewed, 130 were definite lung cancer with a tissue diagnosis, 13 were possible lung cancer, and 68 were cases on which tissue or vital information was not available. Histologic slides that were available from the uranium miner and control cases were reviewed by 3 of the authors (GS, OA, MK) as a panel. Slides from controls and uranium miners were presented randomly to the pathologists without information as to occupational background of the case. Each pathologist independently examined and recorded his diagnosis, using the WHO international classification of lung malignancies9 with the slight modifications used by Yesner et al.17 This classification is as follows: 1. Epidermoid (squamous carcinomas) A. Squamous with pearls and intercellular bridges B. Squamous with intercellular bridges C. Sheet arrangement (equivalent to former "poorly differentiated epidermoid") 2. Small cell anaplastic carcinomas A. Small cell undifferentiated (oat cell) B. Small cell undifferentiated, similar to oat cell, but with larger or polygonal cells 3. Adenocarcinomas A. Acinar type adenocarcinoma B. Papillary adenocarcinoma C. Poorly differentiated adenocarcinoma 4. Large cell undifferentiated 5. Combined epidermoid and adenocarcinoma 6. Other Only after completing their individual diagnoses did the 3 pathologists compare classifications. When discrepancies existed, slides were reviewed and generally the 3 agreed upon the classification. In those cases where agreement was not complete, a consensus has been used. In one uranium miner, 2 different primaries were identifiedepidermoid (IA) and oat cell (). This miner has been treated as 2 cases. He was 49 years old and had 4354 WLM exposure. In another uranium miner, a single tumor had both epidermoid (IC) and undifferentiated () elements. Because of short survival (3 months after first symptom), this case was considered for analytical purposes. He was 56 years of age and had 3130 WLM exposure. As indicated above, attempts were made to eliminate possible bias in readings, but completely "blind" readings were not possible, as many slides of lung tissue had sufficient fibrosis and pigmentation to identify miners. Some nonuranium miners (hard rock and coal) were included with the controls, and the pathologists were advised of this. All 3 pathologists maintained as objective an attitude as possible. The 28 cases of possible lung cancer were reviewed by the pathology panel. When the pathologists were in doubt as to the origin of the cancer, but the clinical data clearly indicated pulmonary origin, their diagnosis of cell type was used in considering it a bronchogenic cancer. When the clinical data was not clear as to primary site (or gave the primary site as other than lung), but the pathologists were reasonably sure that it was a bronchogenic cancer, the cell type diagnosed by the panel was used in considering it a bronchogenic cancer. Using these criteria, 5 doubtful uranium cases and 8 doubtful control cases were included as primary bronchogenic carcinomas. The other were rejected. Information on tobacco habits, occupation (including names and dates of working in mines), birthdates, etc., was obtained primarily by using a standard questionnaire to interview surviving relatives. This method provided incomplete information, so it was supplemented by data from hospital records, from state vital statistics offices, from physician records, and from interviews with miners conducted in the course of an epidemiologic study.10 The cumulative radiation exposure of each man who had mined uranium was assessed by the method described elsewhere.1" Many measurements of radon daughters in the air of uranium mines are available, but these measurements give incomplete coverage, necessitating the use of many estimates in arriving at the radiation exposure for each man. This exposure is expressed as multiples of a Working Level Month (WLM), which is 1.3 x lo6 Mev of potential alpha energy from radon daughters per liter of air in the mine, in which a

3 KO. 8 LUNG CANCER AMONG URANIU MINERS man works 40 hours per week for 4.5 weeks. Because of the estimates used in calculating the WLM, the incomplete histories as to identity of and time spent in each mine, the WLM value used for individuals is not precise. It is, however, sufficiently accurate to usually place each case correctly when the men are divided into exposure groups, as attested by the high correlation previously shown between WLM estimates and lead210 found in bone?." Because of a finding previously reported that the cell type distribution within a group of uranium miner lung cancers was dependent on cumulative radiation,la the above WLM estimates were used for subdividing the uranium miner cases, as shown in Tables 13. Because age and tobacco use are known to influence the frequency of cell types among groups of lung cancer patients? a matching procedure was used for uranium miners and controls. Preliminary inspection indicated that there were insufficient control cases under 55 years of age to completely match the younger age uranium miner cases. Since the matching procedure appeared to be most important for seeking differences among the less exposed groups, the uranium miner cases were arranged in ascending order of WLM estimate. The uranium miners were matched in this order, starting with the least exposed. The control case which most closely matched each uranium miner in age at cancer diagnosis and in cigarette smoking habit was chosen. Pipe and cigar smoking was disregarded. Average cigarettes per day was given priority over pack years in making the matches. Cell type of tumor was concealed during the matching process. This procedure resulted in very close matching for the 40 to 200 WLM and the 201 to 700 WLM groups. The matching in the 701 to 1200 WLM group was nearly as good, but there were 3 cases aged 40 to 49 who had to be matched with 58 or 59yearold controls, and the cigarette smoking could not be matched quite as closely as in the 2 lower WLM groups. In matching the 1201 to 2500 WLM and 2501 to 9700 WLM, it became increasingly difficult to match the miners under 55 years of age and miners who were light smokers. The mean values for these factors is given in Table 2 for each group, reflecting the closeness of overall matching. An item of interest in connection with radiationinduced tumors is the period between exposure and tumor development. Since the I d 3 NY Saccomanno et al. m N 44 e 0 517

4 ~~~ ~~ ~ ~~~ 518 CANCER March 1971 TABLE 2. Comparison of Uranium Miners and Control Groups Vol. 2i WLM Control WLM Control WLM Control WLM Control WLM Control Mean age, years Mean cigarette pack years Mean cigarette/day Inductionlatent period 16.2(248) 10.6(221).5(754) 19.2(741) 18.2(731) mean and range (yrs.) Ratio of Uminers/ controls Ratio of. B. C among Uminers/controls radiation exposure of most uranium miners occurs over a period of several years during which the intensity of exposure varies considerably, there is no single point in time at which one can say the radiation exposure or the tumor induction occurred. Since it is unlikely that radiation tumors are induced on the first day of uranium mining, one must consider that there is a variable induction period while mining uranium, followed by a variable latent period which is characteristic of radiationinduced tumors. Because of our inability to distinguish these 2 periods, we have termed the time between first underqround uranium work and the diagnosis of lung cancer as the inductionlatent period. The mean inductionlatent period has been determined for different exposure groups (Table 2). It has also been determined for different cancer cell types (Table 3). Because of the possible interrelationship of radiation exposure, cigarette smoking, and age, the uranium miner lung cancer cases were divided into groups on the basis of these 3 factors. Eight groups resulted from dividing the men into high or low subgroups for each of these 3 factors. The cell type distribution was determined for each group. The association between cell type and WLM, as demonstrated in Fig. 1, was found to exist throughout all group comparisons, regardless of age and cigarette factors. Because of the small numbers in some of the groups and this constant influence of WLM, the groups were consolidated, leaving only 4 groups, divided on the basis of age at cancer diagnosis and of cigarette usage, as TABLE 3. Mean InductionLatent Period of Lung Cancer among Uranium Miners by Cell Type and by Cumulative Radiation ExDosLrre WLM WLM I nductionlatent Period I nductionlatent Period!w.) (yrs.) WHO Cell type class. Number Mean Range Number Mean Range 1 I Epidernioid 1B c Small cell undifferentiated Adenocarcinoma B c 1 16 Large cell Mixed All epidermoid All small cell undifferentiated All other

5 60 1 I I 50 1 FIG. 1. Relative fre P quency of different histologic types among 9 40 uranium miner lung LL carcinomas. Controls O are plotted at 0 WLM; z uranium miners are divided into 5 cumu g lative radiation exposure groups. I l l 70 I I I 2o L, &.. ~ \ :, Q A Or /,;.<:......,@J 8,.,% 4 L ~... 9 c3 EP_IDERMOID_. _OTHcR El I I I A given in Fig. 2. The low cigarette group consisted of nonsmokers, and those smokers who had averaged less than 20 cigarettes per day while smoking regularly, or had quit smoking 10 years or more prior to cancer diagnosis (regardless of intensity of smoking). The high cigarette group therefore consisted of men who had averaged 20 or more cigarettes per day and had not quit more than 10 years prior to cancer diagnosis. Because of the small number of cases with ethnic differences (4 were American Indians) and with foreign countries of birth (2 uranium miners and 5 controls), these 2 items were disregarded in the matching and analytical procedures. RE~ULTS The result of analyzing the cell type distribution of lung cancers among uranium miners compared to that of matched controls is given in Table 1 and is displayed graphically in Fig. 1. The frequency of cell types for all 121 controls is used for the zero WLM point in Fig. 1. It is apparent that the frequency of both small cell undifferentiated cell types ( and ) increases sharply with increases in radiation exposure up to about 00 WLM, beyond which a high plateau is reached. The type, however, reaches a higher plateau than does the or oat cell type. The frequencies for the epidermoid and other (WHO 3,4, 5) cell types fall rapidly with increasing radia tion exposure to about 00 WLM, beyond which they level off. The epidermoid types appear to fall more rapidly than do the other cell types. The frequencies for both epidermoid and other cell types level off at about 00 WLM. It is instructive to look at the ratio between cell types among the uranium miners and those among their matched controls. When the number of small cell undifferentiated types found among each group of uranium miners is divided by that among their matched controls, the ratio ascends with increasing WLM as indicated in Table 2. In comparison, a similar ratio for the epidermoid cell types descends with increasing WLM, as indicated in Table 2. With both ratios, there appears to be a leveling off at the high end of the WLM scale. A statistical test of significance for differences in matched samples11 was applied to the small cell undifferentiated cell type in each of the WLM groups. In all but the WLM group, this difference was significant at the 95% confidence level. Although the cell type change among the WLM group was not statistically significant, the trend of change was definitely consistent with the significant changes seen at higher levels, as illustrated in Fig. 1. The inductionlatent periods given in Table 2 vary somewhat from the low exposure groups to the high ones, being somewhat

6 520 loo r 95 m 90 P : Z ; H ~ t 20 I I Ago 01 Cancer ss+ IS+ C8pamles/Dq ConrinOrovp I % ~*omr..iittpes 0 zn mi tm 2)1 C.1 typ. ~ l ~, l B. I c *B,~~~I~.~II, O..~.~ ip(ou man LW..~ ir.qu.nw 01 thd IYP omao otm.r PIOYDB. CANCER March 1971 VOl lYp.l FIG. 2. Relative frequency of different histologic types among uranium miner lung carcinomas, as related to age at cancer, and to cigarette smoking habits. longer among men in the higher exposure groups. It is noteworthy that among the 3 highest WLM groups, the minimal inductionlatent period is 7 years. Because of the possibility that the inductionlatent period might vary by both cell type and radiation exposure, the mean inductionlatent period was determined by cell type and by 2 exposure groups. The results are shown in Table 3. The mean inductionlatent periods of the 6 major groupings are fairly uniform with one notable exception. This is the 9.4 year mean among the low exposure groups who had small cell undifferentiated carcinomas. This value is significantly different (p<0.005) from the 17.9 year inductionlatent period noted among the comparable high exposure group. The graphs in Fig. 2 show the results of seeking associations between cell type and cigarette smoking or age at cancer diagnosis. Since the effect of WLM was uniform throughout the 4 cigarette and age groupings, it was ignored here. The relative frequency (in per cent) of each cell type is shown. The various frequencies were compared, and differences were tested for significance by the method of Bross.6 The frequency of epidermoid cancers (la, lb, 1C) was significantly greater among the older miners, but there was no consistent association of this cell type with cigarette smoking. The frequency of oat cell () carcinomas among uranium miners showed no consistent relationship with either age or cigarette smoking, but the young heavy smokers had a significantly higher frequency of this cell type than did the young light smokers. The frequency of small polygonal or round cell carcinomas () showed no consistent relationship with either cigarette smoking or age, but the older heavy smokers had a lower frequency of this cell type than did any of the other groups. DISCUSSION The finding in this study of a high relative frequency of small cell undifferentiated carcinomas confirms and extends the earlier report on American uranium miners.13 It is also consistent with reports of a similar high frequency among Newfoundland fluorspar miners who had excessive exposure to radon daughter products,l2 and with both old and recent reports from Europe regarding the Schneeberg and Joachimsthal miners who mined ores of uranium, silver, cobalt, and arsenic.6. 8 The observation that the frequency of and cell types increases equally among the lower WLM groups but that the frequencies are quite different among the higher WLM groups is puzzling. No explanation for this is apparent. Since both have similar biological behavior, and since the 2 groups seem to merge morphologically, the distinction between them may not be meaningful. The breakdown of the epidermoid cell types into (welldifferentiated), 1B (moderately differentiated), and 1C (slightly differentiated) is puzzling when the uranium miners' cancers are compared with the controls. Among the uranium miners, very few 1B or 1C cell types are noted, whereas among the controls approximately half the epidermoid tumors were of the 1B and 1C cell types. The epidermoid carcinomas among uranium miners that were not welldifferentiated were ei

7 so. 3 LUNG CANCER AMONG URANIUMINERS Succomunno et al. 521 ther converted by radiation into undifferentiated cell types or simply did not arise among this group. The leveling off in the frequency curve seen among the epidermoid and "other" cell types above approximately 00 WLM suggests that some of them may be induced by radiation, but at a much lower rate than are the small cell undifferentiated types. This is consistent with the postulate that the different cell types arise from different cell populations. The fact that the cell type distribution in the WLM group followed the trend, which was significant among higher WLM groups, makes it appear likely that the cell type distribution among the WLM group was influenced by their radiation exposure. This influence, however, was much less marked than was seen at higher exposures. This change among the lowest WLM group is consistent with a recent report that an increased frequency of small cell undifferentiated carcinoma was observed among South African gold miners, most of whom had less than 100 WLM exposure.lb The only consistent association found between cell type and cigarettes or age at cancer development was a relatively weak association between increased age and epidermoid carcinomas. The only significant associations with heavy cigarette smoking were a high frequency of the cell type among younger miners, a low frequency of the cell type among older miners, and a high frequency of epidermoid types among older miners. The inconsistency of the relationships between cigarette smoking and the histologic types seems to negate their significance. It may be concluded that among uranium miners, cigarette smoking is a potent cocarcinogen in the cause of lung cancer, but exerts little, if any, influence on the cell type of lung cancer, but that age may exert a weak influence. Since the population from which the lung cancers among the lowest WLM groups were drawn was much larger than that from which cancers among the highest WLM groups were drawn, there are undoubtedly more "spontaneous" lung cancers included with the cancers in the lowest WLM groups. The "dilution" effect of these "spontaneous" cancers no doubt decreases with increasing WLM, and must be nearly absent above 00 WLM. This suggests the possibility that the cell type shifts associated with increasing WLM are really only a reflection of the degree of "dilution" caused by spontaneous lung cancers. If true, then the radiationinduced lung cancers would have the same cell type distribution regardless of magnitude of exposure. Most of the men with 7 to 10year inductionlatent periods among the highest exposed groups had quite high initial exposure rates. It is tempting, therefore, to postulate that their malignancy was induced in the first year of exposure, and that 7 years represents a minimal latent period for radiationinduced lung carcinoma. There are 9 cases with less than a 7year inductionlatent period (all with less than 700 WLM exposure). The cell types among these 9 are 3 epidermoid, 5 small cell undifferentiated, and one large cell undifferentiated. Although the sample is very small, it does not appear to have a normal cell type distribution. We, therefore, do not feel justified in discarding them. The short inductionlatent period among the low exposure, small cell undifferentiated group was quite surprising. This one group accounts for most of the inductionlatent period difference observed between high and low exposure groups. The 16 cases in the low exposure, small cell undifferentiated group were examined to see if their age, mining, or cigarette smoking habits were different from other groups. The mean cigarettes per day among them was 20.4, the mean pack years of cigarettes was 32.2, their mean age was 52.9, and 12 had done much other hard rock mining before mining uranium. Their cigarette smoking and age were similar to that of all men in the WLM groups, but their prior hard rock mining experience was different. When their inductionlatent period is calculated from first hard rock mining to lung cancer, the mean becomes 25.1 years instead of 9.4. Neither cigarettes nor age appear to be a factor in the short inductionlatent period of this group, but prior mining experience may be. It appears that either there was sufficient radiation exposure in the nonuranium mines to induce the cancer, or the prior exposure to mine dust had made the miners especially susceptible to exposures in uranium mines. There are other possible explanations, such as that these men might have been especially susceptible to lung cancer induction,l4 or that these cases represent tumors produced by a different mechanism than others (similar to alternate mechanisms proposed elsewher@* ), these being a special low dose, short latent period type of tumor.

8 522 CANCER March 1971 VOI. 27 Because of the possibility that there might have been some inadvertent selection of cases for panel review, the cases not reviewed by the panel were considered. The pathologist s description of the tumors on 38 of the controls was reviewed. The breakdown for this group of 38 was 25 epidermoid, 9 undifferentiated, and 4 adenocarcinomas. The mean age of these 38 men was 66.8 years. The older than average age of this group reflects the fact that greater effort was exerted in locating tissue from men under 55 years of age, as it was known that matching problems would occur in this age group. Of 31 uranium miner cases on which no tissue was available, a pathologist had described the tumor in 19. The breakdown of these 19 was 5 epidermoid, 13 undifferentiated, and one adenocarcinoma. Their mean age was 52.7 years. Although some of these cell type designations might have been changed by the pathol TABLE 4. Comparison of WLM Values Derived from Occupational History and from 210Pb Analysis of Bone Defatted Rib 210Pb at WLM Histologic Years from start of WLM estimate from death calculated type of Case no. Umining to death occupational history pci/g from 210Pb cancer c 3B 1B 2R 1B, 3A 3A

9 No. 3 LUNG CANCER AMONG URANIUMINERS * Saccornanno et al. 523 ogy panel, it is not likely that many of them would have been changed as the cell type distributions of the cases on which tissue was not available were quite similar to the corresponding larger group which was reviewed. It is concluded that there is no evidence of a selection bias in obtaining tissue from the uranium miner and control cases. Determination of 210Pb was made at death one some of the miners included in this study. Most of these values have been reported elsewhere,23 * relating the measurements to radiation exposure. Using a modification of the method of Blanchard4 for adjusting for excretion, we have calculated the probable WLM value represented by the bone zlopb for each of 42 cases. With some exceptions, these values (Table 4) are generally in reasonable agreement with the WLM derived from the occupational histories. There would be some shifting of men between WLM categories if the estimates based on 2loPb were used, but it would produce little change in Tables 13. It may be noted that for most of the men who started mining uranium 20 or more years be fore death, the WLM calculated from 210Pb is higher than that obtained from occupational histories. The reason for this is probably due to an overcorrection for excretion of zlopb during the long time period between exposure and death. This overcorrection is obvious in cases 48, 51, and 93, where unrealistically high values were calculated. Other factors which may affect the relationship between bone 2loPb and WLM are variations in individual retention of radon daughters, in metabolic differences between individuals, in contribution to bone zlopb from sources other than radon daughters, and in a possible acceleration of lead excretion during terminal debilitating illness. Since the ZloPb values are more objective than the occupational history estimates, it would have been preferable (in spite of the drawbacks) to have used them as the basis for exposure ranking of miners in this study. However, since zlopb values were available on less than half the subjects, it was felt best to keep all the WLM estimates based on the same criteriawhich in this case had to be occupational history. REFERENCES 1. Archer, V. E., and Lundin, F. E., Jr.: Radiogenic lung cancer in man: exposureeffect relationship. Enuiron. Res. 1:370383, Black, S. C., Archer, V. E., Dixon, W. C., and Saccomanno, G.: Correlation of radiation exposure and lead210 in uranium miners. Health Physics 14:8193, Blair, H. A.: Dosetime relations for induction of lung Cancer in uranium miners. Symposium of RadiationInduced Cancer, April 28May 2, 1969, International Atomic Energy Agency, Athens. 4. Blanchard, R. L., Archer, V. E., and Saccomanno, G.: Blood and Skeletal Levels of 210 Pb210 Po as a Measure of Exposure to Inhaled Radon Daughter Products. Health Phys. 16:585596, Bross, I. A.: Confidence interval for a percentage increase. Biometries 10:245250, Gates, O., and Warren, S.: Histogenesis of lung carcinoma in mice induced by gamma radiation. Arch. Path. 71~693713, Hearings before the Subcommittee on Research, Development, and Radiation, of the Joint Committee on Atomic Energy, Radiation Standards for Uranium Mining, March 17 and 18, 1969, and Radiation Exposure of Uranium Miners, May 9, 10, 23, June 69, July 26 and 27, and August 8 and 10, U.S. Government Printing Office, Washington, D.C. 8. Horacek, J.: Der Joachimstaler Lungerkrebs Nach dem Zweiten Weltkrieg (bericht Uber 55 falle). Z. yrebsforsch , Kreyberg, L.: Histological lung cancer types: a morphological and biological correlation, Norwegian University Press, Oslo, Lundin, F. E., Jr., Lloyd, J. W., Smith, E. M., Archer, V. E., and Holaday, D. A.: Mortality of uranium miners in relation to radiation exposure, hard rock mining and cigarette smokingthrough September Health Phys. 16:5778, Maxwell, A. E.: Analyzing Qualitative Data. New York, John Wiley and Sons, Report of Royal Commission, Respecting Radiation, Compensation and Safety at the Fluorspar Mines, St. Lawrence, Newfoundland, Canada, 1969; p Saccomanno, G., Archer, V. E., Saunders, R. P., James, L. A., and Beckler, P. A.: Lung cancer of uranium miners on the Colorado plateau. Health Phys , Saccomanno, G., Saunders, R. P., Klein, M. G., Archer, V. E., and Brennan, L.: Cytology of the lung in reference to irritatants, individual sensitivity, and healing. In press.. Tamplin, A. R., and Gofman, J. W.:The Colorado Plateau: Joachimsthal Revisited? An analysis of the lung cancer problem in uranium and hardrock miners. Testimony presented at Hearings of The Joint Committee on Atomic Energy, 91st Congress of the U.S., January 28, Webster, I., and Basson, J. K.: Bronchogenic carcinoma in South African gold miners. Presented at the International Conference of Pneumoconiosis, Johannesburg, May 2, Yesner, R., Gerstl, B., and Auerbach, 0.: Application of the World Health Organization classification of lung carcinoma to biopsy material. Ann. Thoruc. Surg. 1:3349, 1965.