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Testimony on H.R. 3539-The "Radiation Workers Justice Act of 1998" by Lawrence J. Fine, M.D., DR.P.H.
Division of Surveillance, Hazard Evaluations and Field Studies
National Institute for Occupational Safety and Health
Centers for Disease Control and Prevention
U.S. Department of Health and Human Services

Before the House Committee on the Judiciary, Subcommittee on Immigration and Claims
June 25, 1998

I am Dr. Larry Fine, Director of the Division of Surveillance, Hazard Evaluations and Field Studies, a research Division within the National Institute for Occupational Safety and Health. The mission of NIOSH is to conduct research and make recommendations to protect workers from illness and injury related to their occupations. I will focus my remarks on what is known about the health effects associated with uranium mining and milling and briefly describe current NIOSH research in this area. I am also submitting for the record a summary of NIOSH scientific research and policy documents pertaining to uranium millers and miners.

Uranium Miners

The health effects of underground uranium mining have been very well studied. In fact, all of the epidemiologic data on uranium miners pertain to underground miners. In the United States, NIOSH has studied a group of uranium miners employed in the Colorado plateau in the 1950's. At least 10 other studies of uranium miners have been done in other countries. The epidemiological evidence that uranium miners experience an increased risk of lung cancer is very strong. The most recent follow-up of the U.S. miners cohort found nearly a 6-fold increased risk for lung cancer for white miners and a 3-fold increased risk for Navajo miners. Both smoking and non-smoking miners have an increased risk of lung cancer.

The risk of lung cancer among underground miners is thought to be due primarily to their exposure to radon decay products, that is, the products of the radioactive breakdown of naturally occurring radon. The unit of exposure is the working level month (WLM). One working level (WL) is any combination of short lived radon decay products in 1 liter (L) of air that will ultimately release 1.3 X 105million electron volts (MeV) of alpha energy during decay to lead-210. The number of WLM is the product of the radon decay products concentration, in WL, and the exposure duration, in months. Radon decay products accumulate in the closed environment of the underground mines. In 1987, a NIOSH criteria document recommended that mine operators limit exposure to radon decay products to the lowest levels possible, and further recommended an upper limit of 1 WLM per year. NIOSH acknowledged that even at the Recommended Exposure Limit (REL) of 1 WLM, significant health risks are expected.

The Advisory Committee on Human Radiation Experiments, which was created by President Clinton in 1994 to review ethical issues in government radiation research, recommended that the Radiation Exposure Compensation Act be reviewed to determine whether the documentation standards for compensation should be changed. As a result of this recommendation, a committee of government scientists and attorneys was established to study the Radiation Exposure Compensation Act Provisions relating to uranium miners and the Department's implementing regulations. The "Final Report of the Radiation Exposure Compensation Act Committee" was submitted to the Human Radiation Interagency Working group in July, 1996; NIOSH considers that committee report an excellent summary of the scientific data.

Uranium miners also have an excess risk for non-malignant respiratory disease, including pneumoconiosis (silicosis), chronic obstructive pulmonary disease and tuberculosis. The most recent follow-up of the U.S. white miners cohort found nearly a 24-fold increased risk for pneumoconiosis (when compared to the general population), a 3.7-fold increased risk for tuberculosis and a 2.8-fold increased risk for chronic obstructive pulmonary disease. The Navajo miners cohort had 2.6-fold increased risk for tuberculosis and a 2.6-fold increased risk for "pneumoconioses and other respiratory diseases". Some or all of these nonmalignant respiratory disease excesses are due to silica and other dusts in the mine environment.

Other diseases which have been found to be elevated in some studies of uranium miners include: leukemia, non-Hodgkins' lymphoma, malignant melanoma, and kidney and liver cancer. However, a recent analysis of 62,209 uranium miners in 11 studies around the world found no strong evidence that uranium miners had increased risk of any cancer besides lung cancer.

Uranium Millers

Uranium millers have not been well studied. Potential exposures in uranium mills differ from those in uranium mines. Although radon decay products are generated in uranium mills, they do not accumulate to the high levels observed in mines. Health concerns for uranium millers center on their exposures to uranium dusts and silica. Exposure to silica and relatively insoluble uranium compounds may increase the millers' risk of non-malignant respiratory disease, while exposure to relatively soluble forms of uranium may increase their risk of kidney disease. The two mortality studies of uranium millers have not had adequate population size or adequate time since exposure to detect even a moderate risk of lung cancer if present; neither study reported an elevated risk for lung cancer. One of the two completed mortality studies of millers found an increased risk for cancer of the lymphatic and hematopoietic organs (excluding leukemia), and the other found an increased risk for non-malignant respiratory disease and accidents. A non-significant excess in deaths from chronic kidney disease was also observed in the second study.

There have been two medical studies of uranium millers, one of which found evidence for pulmonary fibrosis (possibly due to previous mining) and the other of which found evidence for kidney damage.

There have been no studies of health effects among former above-ground uranium miners.

NIOSH has two studies underway to learn more about the health effects of uranium milling. We are updating the mortality experience of the larger of the two prior mortality studies; this should provide much improved information about the risk of lung cancer. We also have a cooperative agreement with the University of New Mexico to conduct a medical study among uranium millers. NIOSH has also awarded a grant to the University of Southern California, School of Medicine to refine dose estimates and reexamine dose response relationships for the Colorado miners cohort.

Mr. Chairman, this concludes my testimony. I would be happy to answer any questions you or other members of the subcommittee may have.

NIOSH Publications Related to Uranium Miners and Millers

Roscoe-RJ [1997]. An Update of Mortality from All Causes among White Uranium Miners from the Colorado Plateau Study Group. American Journal of Industrial Medicine31(2):211-222.

The standardized mortality ratios (SMRs) and standardized rate ratios (SRRs) for uranium miners were updated. Information was obtained for 3,238 white, male uranium miners from the Colorado Plateau study group. Vital status was determined from 1960 to 1990. The working level months (WLMs) of radon progeny exposure were calculated for the cohort members. Of the 3,238 workers investigated, 1,595 were dead. The SMR for all causes was elevated at 1.6. Other elevated SMRs included 3.7 for tuberculosis, 4.8 for breast cancer, 5.8 for lung cancer, and 24.1 for pneumoconiosis. For the 371 workers who died of lung cancer, the mean radon progeny exposure level was 1,574 WLMs. The lung cancer rate increased significantly with increasing radon progeny exposure, from an SRR of 1.0 with less than 120 WLMs to an SRR of 7.2 with more than 1,000 WLMs. The lung cancer rate also increased significantly with increasing duration of employment, with an SRR of 1.0 with less than 5 years of employment to an SRR of 3.9 with greater than 15 years of employment. The SRRs for benign and unspecified tumors increased significantly with increasing duration of employment, ranging from 1.0 with less than 5 years of employment to 3.7 with greater than 15 years of employment. The SRRs for pneumoconiosis also increased significantly with increasing duration of employment, varying from 1.0 with less than 5 years of employment to 19.2 with greater than 15 years of employment. For accidental injuries, the SMR was highest for the workers employed less than 5 years, with a value of 3.9, and lowest for the workers employed more than 15 years, with a value of 2.5. The author concludes that the most serious mortality risks for uranium miners are lung cancer, pneumoconiosis, and chronic obstructive respiratory disease.

Brenner-DJ, [1994]. The Significance of Dose Rate in Assessing the Hazards of Domestic Radon Exposure. Health Physics 67(1):76-79.

The possibility that domestic radon exposure is underestimated by studies performed on uranium (7440611) miners because domestic exposure occurs at lower rates than uranium miners was examined. A biophysical model which suggested that cells in a certain period of their growth cycle were more sensitive to radiation than cells not in this period was used. Basic biophysical arguments implied that if a target cell is hit by one or zero alpha particles, it cannot show a dose rate effect of any kind. The resulting overall effects result from a complex interplay between cumulative exposure and exposure rate. The protraction effect increases as the exposure rate decreases, and decreases as the cumulative exposure itself decreases. Domestically, an average lifetime exposure of about 14 working level months results in less than 1% of segmental bronchioepithelial cell nuclei receiving a multiple traversal. In miner studies, even though exposure rates are higher, it is compensated for by higher exposure, which results in significant protraction related enhancement. The author cautions that this conclusion is essentially model independent, depending only on the theory that a significant dose rate effect of any kind requires the exposure of target cells to multiple alpha particle traversals.

Roscoe-RJ; Deddens-JA; Salvan-A; Schnorr-TM [1995]. Mortality among Navajo Uranium Miners. American Journal of Public Health 85(4): 535-540.

The cancer and mortality risks of Navajo males exposed to radon (10043922) progeny were updated in a new analysis of cohort mortality data for male Navajo uranium miners (SIC-1094) from the Colorado Plateau study group. A study group of 757 male Navajo uranium miners was selected from a group of individuals who worked at least 1 month underground in a uranium mine and were examined in the Public Health Service medical surveys between 1950 and 1960. Working level months of radon progeny exposure for subjects were determined by multiplying underground working months by the working level of the mine involved. Vital status was determined through analysis of Social Security Administration, Internal Revenue Service, National Death Index, Health Care Financing Administration and Indian Health Service records. Mortality ratios were calculated and used to conduct a life table analysis. A Cox regression analysis was used to account for disease mortality risk factors. Mortality from heart, circulatory and digestive diseases were found to be elevated in the study population, as were the incidences of lung cancer, tuberculosis, pneumoconioses and other respiratory diseases. The authors conclude that increased duration of exposure to underground uranium mining is related to increased mortality risk for lung cancer, pneumoconioses and tuberculosis in Navajo miners.

Steenland-K[1994]. Age Specific Interactions between Smoking and Radon among United States Uranium Miners. Occupational and Environmental Medicine 51(3):192-194.

The Hornung and Meinhardt analyses was reexamined to determine age specific interactions between smoking and radon (10043922) exposures in uranium miners working in the United States. Rates for lung cancer among never smoking United States veterans (R0), for ever smoking United States veterans (R1), for never smoking miners exposed to radon (R2), and for ever smoking miners (R12) were compared. The predicted death rates from lung cancer for the R12 category were compared under the additive and multiplicative models. The observed rates were intermediate between those of these two models. The multiplicative model fit the data more closely than the additive at the youngest and oldest age categories. The author notes that the data are limited by small numbers and lack of quantitative data on smoking and exposure to radon daughters for the development of the rate ratios. In this study there were only 14 deaths due to lung cancer among miners who never smoked. The author suggests that perhaps an even greater difficulty or limitation is the lack of understanding of the underlying mechanisms affecting rates at a biological level in that the mechanism by which either smoking or radon cause lung cancer is not totally clear.

Hornung-RW; Meinhardt-TJ [1986]. Quantitative Risk Assessment of Lung Cancer in U.S. Uranium Miners. NIOSH, Cincinnati, Ohio:1-52.

The mortality experience of a cohort of 3346 underground uranium miners evaluated in 1977 was updated through 1982. As of 1982, there were 1214 miners who were deceased; 255 had died of lung cancer. Variables considered in the development of the model included cumulative exposure, exposure rate, cumulative cigarette smoking, smoking rate, age at initial exposure, calendar year of initial exposure, birth year, height, duration of underground employment, and years of prior hardrock mining. Cumulative cigarette smoking and cumulative radon daughter exposure had a joint effect intermediate between additive and multiplicative, implying a synergistic relationship. Results indicated that modeling cumulative exposure alone may not adequately predict the relative risk of lung cancer from chronic exposure to radon daughters. Miners receiving a given amount of cumulative exposure at lower rates for longer periods of time were at greater risk relative to those with the same cumulative exposure received at higher rates for shorter time periods. Data suggested that radon daughters act at a late stage in the carcinogenic process. The epidemiologic model developed for this study was found to provide a very good fit to data from 60 to 6000 working level months.

Ravenholt-RT; Kuller-LH; Roscoe-RJ; Steenland-K [1989]. Radon and Smoking Status. Journal of the American Medical Association 262(24):3403-3404.

These two letters to the editor and the reply to them concerned a NIOSH study of lung cancer mortality among uranium miners who did not smoke cigarettes but who were exposed to radon daughters. The first letter noted two flaws of the study, the first being that no validation was done of the lifelong nonsmoking status of the 14 lung cancer decedents by discussions with surviving relatives, coworkers and physicians. The second flaw noted was that no attention was given to the issue of what proportion of radon daughter alpha particle exposure was due not to uranium in mine ore but to tobacco smoke polonium-210 (7440086) present in mines, bars and home environments as generated by associates of the affected workers. The second letter to the editor contended that the conclusions of the original study were not consistent with the findings, suggesting that the conclusions drawn describe the cases that might exist with more cases in the study rather than stating conclusions based solely on the cases which were studied. These issues were addressed in the reply by the original authors.

Wasserman-DE; Behrens-VJ; Pelmear-PL; Ilka-R; Reynolds-DD; Doyle-TE; Samueloff-S; Goff-RJ [1991]. Hand-Arm Vibration Syndrome in a Group of U.S. Uranium Miners Exposed to Hand-Arm Vibration. Applied Occupational and Environmental Hygiene 6(3): 183-187.

A group of 134 uranium miners participated in medical evaluations in New Mexico in an effort to explore hand/arm vibration syndrome (HAVS). Jack leg type drills were used on the job by 92 of these workers. While four of the miners operated two jack leg type drills and a jack hammer, engineering evaluations were carried out. After screening for confounding exposures or medical conditions, 49 miners were selected, 17% of whom were in the vascular stages of Hand/Arm Vibration Syndrome and 24% in the neurologic stages according to the Taylor/Pelmear Classification System. A median latency of 4.5 years for tingling, numbness, and blanching was observed. A range of unweighted vibration acceleration levels of 5.16 to 19.04 grams (root mean square) in the axial tool axis was measured on three pneumatic tools including both a small and large jack leg type drill and a small jack hammer. These results revealed a lower rate of HAVS, a longer latency of HAVS, and lower vibration levels among workers using jack leg type drills compared with earlier results for workers using chipping and grinding tools. The authors conclude that exposure to hand/arm vibration from the jack leg type drill could not be considered safe as workers with HAVS were identified.

Halperin-WE; Beaumont-JJ; Waxweiler-RJ [1989]. Lung Cancer Mortality among Nonsmoking Uranium Miners Exposed to Radon Daughters. Journal of the American Medical Association, 262(5):629-633.

A cohort mortality study of 516 white, male, nonsmoking uranium miners was performed to identify risk factors associated with lung cancer in this occupational group. Only men who had never smoked were selected from a larger cohort which had been followed for 35 years. Radon daughter exposure was expressed in terms of working months (WLM). Vital status was determined for each cohort participant from linkage with various federal records. Data were analyzed by a life table system developed for NIOSH. Person year calculations were made for strata defined by age, WLM, calendar periods, and periods after first uranium mining. Expected number of deaths was estimated, and standardized mortality ratios (SMR) were calculated. Comparisons were made with nonsmoking veteran's mortality rates, and with the general United States nonsmoking population. Mean age for living participants at the end of study was 56 years. Mean time in underground uranium mining was 52 months. Median radon daughter exposure was 296 WLM. Mean time from first mining employment to death or end of study was 28 years. A total of 14 lung cancer deaths were found. The SMR based on the veterans' comparison was 12.7. The Axelson rate comparison included 77 additional participants who were cigar and pipe smokers; 19 lung cancer deaths were found in this augmented cohort, resulting in an SMR of 9.3. The SMR calculated for nonmalignant respiratory disease mortality was 11.7. The authors conclude that exposure to radon daughters in nonsmoking underground uranium miners increases the risk of lung cancer death 12 fold.

Craft-BF; Oser-JL; Norris-FW [1966]. A Method for Determining Relative Amounts of Combined and Uncombined Radon Daughter Activity in Underground Uranium Mines. American Industrial Hygiene Association Journal 27:154-159.

A method is described and tested for determining relative amounts of combined and uncombined radon daughter activity in underground uranium mines. It is based on the different diffusion coefficients of atomic size radon daughter products compared with those combined with particulates and operates by means of a diffusion tube that separates out a calculable fraction of the atomic-size daughter products and permits larger particulates to pass through the tube. A table summarizes the field studies in several underground uranium mines in southern Utah and Colorado. The amount of uncombined radon daughter activity ranges from almost zero up to 73 percent. This wide ranges indicates that it would be impossible to select any particular fraction of uncombined atoms as representative of actual mine conditions. Factors affecting the percentage of radon daughter atoms existing in the uncombined state are the atmospheric concentration of particulates, the amount of water vapor in the air, and the rate of air change in the area. It appeared that in areas where diesel smoke was present the fraction of uncombined daughters was low. It is stressed that if there is a difference between the combined or uncombined state as far as effective radiation dose is concerned, then this method of distinguishing between the two states would be critical in estimating effective exposure.

Holaday-DA; Jones-JH [1973]. Evaluation of Uranium Mine Atmospheres by Measurements of the Working Level and Radon. Radiation Data and Reports, United States Environmental Protection Agency 14( 11):653-657.

Using estimates of equilibrium ratios and concentrations of unattached atoms in uranium 7440611) mines, calculations were performed and results presented of the amount of alpha energy per liter of air per working level available to be imparted to the various regions of the respiratory tract. It was discovered that the factor that caused the greatest effect on the alpha energy that could be deposited in the lungs was a change in the unattached fraction of the radon daughters. If the radon (10043922) concentration was used to determine potential exposure, radon to daughter ratios also had a marked effect on the potential alpha energy deposition.

Cross-FT; Bloomster-CH; Hendrickson-PL; Nelson-IC; Hooper-BL; Merrill-JA; Stuart-BO [1974]. Evaluation of Methods for Setting Occupational Health Standards for Uranium Miners. Battelle, Pacific Northwest Laboratories, Richland, Washington:1-312.

A review is made of the methods employed in development of radiation exposure standards for uranium (7440611) mines over the past 30 years. The process of imposing standards to identify factors important in evolving standards is examined with a view to develop protection against future toxic agents. Topics include methods for setting radiation exposure standards for uranium miners epidemiology of European and American uranium miners, other groups exposed to radon (10043922) and radon daughters, Newfoundland fluorspar miners, British iron (7439896) miners, Russian manganese (7439965) miners, potash miners, Swedish zinc (7440666) miners, relationship of cost to mine operators and incidence of respiratory cancer deaths, costs to government and society of exposure standard setting methodologies; comparison and selection of exposure standards and exposure standard setting methodologies, and factors influencing enforcement of exposure standards.

Archer-VE; Gillam-JD; Wagoner-JK [1975]. Respiratory Disease Mortality among Uranium Miners. NIOSH, Salt Lake City, Utah:1-19.

Mortality analysis on a group of White and one of American Indian uranium miners shows a significant excess of respiratory cancer among Indians. Non-malignant respiratory disease deaths among the Whites are considered due to diffuse parenchymal radiation damage leading to cancer. Exposure-response curves for nonsmokers are linear for both respiratory cancer and other respiratory disease. Cigarette smoking elevates and distorts that curve. Light cigarette smokers appear to be most vulnerable to lung parenchymal damage.

Raghavayya-M; Jones-JH [1974]. A Wire Screen-Filter Paper Combination for the Measurement of Fractions of Unattached Radon Daughters in Uranium Mines.

Lack of current actual field data on such factors as radon daughter equilibrium ratios and fractions of unattached radon daughter atoms and the relationship of the measured working levels to actual lung dose caused questioning of the working level concept as the basis for mine radiation control work. A simple technique for measuring equilibrium ratios and the fractions of unattached radon (10043922) daughter atoms in air using a wire screen prefilter to collect unattached atoms is described. Values obtained by this method in several United States uranium (7440611) mines are presented.

Saccomanno-G; Archer-VE; Saunders-RP; Auerbach-O; Klein-MG [1976]. Early Indices of Cancer Risk Among Uranium Miners With Reference to Modifying Factors Annals of the New York Academy of Sciences 271:377-383.

Early indices of cancer risk among uranium (7440611) miners were investigated prospectively since 1957 in a population of uranium miners, via yearly sputum cytology. Autopsies were performed on 120 miners with lung cancer and on 26 miners dying from other causes. The results show that cancer of the lung develops from normal epithelial changes that progress from regular squamous cell metaplasia to progressively more and more atypical stages to eventually develop into squamous-cell carcinoma in situ. The in situ stage sheds large numbers of cells that can often be identified as malignant cells in sputum. This allows early diagnosis, localization, and resection, increasing, it is hoped, survival from bronchogenic carcinoma.

Rodgers-JC [1974]. Radon Progeny Exposure Measurement Using Lead-210. Western Area Occupational Health Laboratory, NIOSH, U.S. Department of Health, Education,

A technique for monitoring the average alpha exposure due to the airborne decay products of radon-222 in a uranium mine atmosphere was described. Sampling was done on a long-term continuous basis. The plan involved the collection of a long term, high volume sample, in which the short lived daughters decay to lead-210 (14255040). These rapidly separate and a liquid scintillation counting technique was used to count the lead-210. During actual testing, while countable quantities of lead-210 were accumulated, only a fraction of the activity could be attributed to the direct collection of short lived daughters. The remainder of the lead-210 was shown to result from a variety of indeterminate background sources. According to the author, these findings raise serious questions concerning the usefulness of measuring accumulated levels of lead-210 whether it be on an air filter or in a blood sample from miners and assuming that it relates directly to radon exposure.

Archer-VE; Brown-MC [1970]. American Uranium Miners and Lung Cancer. Pneumoconiosis, Proceedings of the International Conference, Johannesburg 1969, H. A. Shapiro, Editor; Cape Town, Oxford University Press:569-571.

Results of periodic examinations of uranium miners in the United States were reviewed and an ongoing follow up mortality study of former miners was described. Individual estimates of cumulative radiation exposure were made for all miners in terms of working level months (WLM) and working level (WL) of exposure to radon (10043922) daughters during the period from 1950 to 1963. Follow up was from 1960 to October 1, 1967. There were 62 cases of lung cancer among 398 deaths recorded in a population of 3,414 uranium miners, as compared to ten cases expected; most of the cancers occurred in miners who had at least 10 years of occupational exposure to uranium mining. The excess of respiratory cancer deaths increased according to the increase of WLM. For estimated cumulative exposure categories up to 839WLM, lung cancer excess was three to four times greater than expected. Above this level, excess lung cancer rates increased markedly with dose, up to about 38 fold excess for exposures over 3720WLM. The excess lung cancer in smokers was ten times higher than that of nonsmokers. Undifferentiated small cell carcinomas, especially of the oat cell type, were the most frequent types of lung cancer among uranium miners, as compared to epidermoid types prevailing in nonminers. It was found that bone and urine levels of lead-210 (14255040) and polonium-210 (13981527) correlated well with exposure levels, and urine levels could be used to estimate exposure provided sufficient time had passed since last exposure. Reference was made to the fact that the permissible levels of exposure to radon daughters in uranium mines were to be gradually lowered from 12 to 4WLM per year starting in 1971.

Fox-DK; Hopkins-BL; Anger-WK [1987]. The Long-Term Effects of a Token Economy on Safety Performance in Open-Pit Mining. Journal of Applied Behavior Analysis 20(3):215-224.

A behavioral safety program using trading stamps as tokens to reinforce safety was studied using the employees of two open pit mining facilities and their product processing facilities. The mines were used in the extraction and milling of uranium ore (SIC-1094) and coal for the electricity generating industry. Mining procedures used included the use of scrapers, large electrical shovels, draglines, diesel electric dump trucks, bulldozers, front loaders, and smaller trucks. The majority of the injuries at both sites were associated with the use and maintenance of heavy equipment. Subjects included the employees of the facilities between 1970 and 1983. Job categories included office workers, engineers, management, custodial and maintenance personnel, production workers, mining equipment operators, and processing operators. Workers were divided into four hazard groups ranked by the number of lost time injuries reported during a baseline period. Trading stamps were given with paychecks to workers who had not suffered a lost time injury or compensation injury and to those under a single supervisor whose group was free of such injuries during the month. Safety awards using stamps were also given for safety suggestions, acts that prevented accidents and property damage, and other useful actions by workers. Use of the token economy resulted in a reduction of the number of worker days lost and the number of lost time injuries at both mines. The costs of the token program were substantially less than the cost attributable to either lost worker days or lost time injuries. The authors conclude that properly administered behavioral programs can be successful for extended periods of time.

Baier-EJ [1976]. Current Intelligence Bulletin 10 - Radon Daughters. Current Intelligence Bulletin 10, NIOSH, U.S. U.S. Department of Health and Human Services, Cincinnati, Ohio:1-2.

A possible health hazard due to emissions of radon (10043922) daughters in caves was discussed. It was reported to NIOSH that measured concentrations of radon daughters in a number of National. Park Service caves were near the OSHA standards for uranium miners Park Service caves in which radon daughter radiation levels greater than 0.30 working levels (WL) were measured included Carlsbad Caverns National Park, New Mexico; Lehman Caves National Monument, Nevada; Mammoth Cave National Park, Kentucky; Oregon Caves National Monument, Oregon; and Round Spring Cave in Ozark National Scenic Riverways, Missouri. It was also found that at Mammoth Cave, buildings above ground that were cooled with cave air had alpha radiation levels of 0.6WL. OSHA standards for uranium miners that were considered appropriate by the Environmental Protection Agency (EPA) for natural caves were given. These indicated that cumulative exposures should not exceed 4WL months (WLmo) in any calendar year. It is noted that EPA does not regard an individual exposure limit of 4WLmo per year to be safe, since the risk of lung cancer would be expected to double after 10 to 20 years exposure. It is recommended that consideration be given to rotating long term employees working in high radiation areas and that radiation levels in state and privately owned caves be measured.

Hornung-RW; Meinhardt-TJ [1987]. Quantitative Risk Assessment of Lung Cancer in U.S. Uranium Miners. Health Physics 5(4):417-430.

Results of a study of quantitative risk estimates of lung cancer incidence subsequent to exposure to radon daughters in 3366 caucasian uranium miners were reported. A previously developed power function risk model provided the best fit to data as measured by the log likelihood. Studies on exposure rates suggested that among groups of underground miners receiving equivalent cumulative exposures, those exposed to lower levels for longer periods of time were at increased risk compared with those exposed to higher doses for shorter periods of time. It was determined that a miner who received a total exposure below 834 units of cumulative exposure at a rate 0.1 times as great as another miner of the same age, smoking status and cumulative exposure, would have a 58 percent greater risk of lung cancer. For miners in the 834 to 10000 units of cumulative exposure range, the increased risk would only be 10 percent at the lower exposure rate. Age was shown to influence cancer risk. For example, a miner who was initially exposed 10 years later in life than another miner with the same radon daughter exposure and smoking history, was shown to have a 32 percent higher risk of lung cancer. Relative risk of lung cancer fell sharply in the years following cessation of exposure.

Nelson-IC; Parker-HM [1974]. A Further Appraisal of Dosimetry Related to Uranium Mining Health Hazards. NIOSH Technical Information, Division of Field Studies and Clinical Investigations, NIOSH, Cincinnati, Ohio, HEW Publication No. (NIOSH) 74-106, Contract CPE-69-131:1-106.

Uranium (7440611) miner lung dosimetry is discussed in terms of: characterization of mine atmospheres; lung model and breathing patterns; deposition of radon (10043922) daughters in the respiratory system; regional translocation and equilibrium activities; and target tissue and dose. Methods are compared for estimating the cancer related dose imparted to the basal cells of the bronchial epithelium resulting from the deposition of alpha emitting daughters of radon-222 on surfaces of the tracheobronchial tree.

Archer-VE; Saccomanno-G; Jones-JH [1973]. Expectancy Calculations for Histological Types of Bronchogenic Carcinoma among Uranium Miners. Western Area Occupational Health Laboratory, National Institute for Occupational Safety and Health, Department of Health, Education, and Welfare (Unpublished; Paper presented at the meeting of . The AAAS, June 11-15, 1973):1-12.

By use of calculations of expected numbers for each of the major histologic types of bronchogenic carcinoma, it was shown that epidermoid, small cell undifferentiated and adenocarcinomas are all increased among uranium (7440611) miners. Small cell undifferentiated was the predominant type and was the only one that was significantly elevated in all cumulative radiation exposure groups. It was noted that the same three groups have been shown to be elevated among cigarette smokers, but with different relative frequencies. Other histologic types (large cell undifferentiated, carcinoid, bronchiolo-alveolar, and bronchial gland tumors) were not elevated in frequency. This data supports the hypothesis that small cell undifferentiated and epidermoid carcinomas of the lung are closely related, and are the principal types whose frequency is increased by inhaled carcinogens, even though adenocarcinomas are also increased to some extent. The frequency of other histologic types (with the probable exception of combined adeno-epidermoid) is apparently unaffected by inhaled carcinogens in man. In all analyses of histologic types of bronchogenic carcinoma, large cell and small cell undifferentiated types should be separated.

Samet-JM; Kutvirt-DM; Waxweiler-RJ; Key-CR [1984]. Uranium Mining and Lung Cancer in Navajo Men. New England Journal of Medicine 310:1481-1484.

A population based case control study was conducted to determine if a single occupational factor, uranium mining, was associated with an increased risk of lung cancer in a predominantly nonsmoking population of Navajo Indians. The cases in this study consisted of 32 Navajo males with primary lung cancer. Comparisons consisted of 64 Navajo males who had died of nonrespiratory cancer. Comparisons were matched to cases within 5 years of age and diagnosis date. Multiple sources were used for all subjects to obtain information concerning smoking and occupation, with particular reference to whether the subjects had ever been employed as uranium miners. A history of being employed as a uranium miner was documented for 23 of the 32 cases, and could not be documented for any of the comparisons. Smoking histories were available for 21 of the 23 affected cases but were unavailable for any of the comparisons. Eight of the 21 cases were nonsmokers. Of the 13 smokers, two smoked less than one cigarette per day, six smoked between one and three per day, and five smoked four to eight cigarettes daily. The statistical association between uranium mining and lung cancer was highly significant. The estimate of relative risk was infinite because no comparisons were exposed, but with use of the binomial distribution the lower 95 percent confidence limit for relative risk was 14.4. The median duration of employment in underground mines was 13 years, while the median duration from start of employment to diagnosis was 23.5 years. The median age of cases who developed lung cancer and were uranium miners was 44 years, while the median age for affected nonminers was 63 years. The authors conclude that uranium mining increases the risk of lung cancer in humans.

Roscoe-RJ; Mason-TJ [1984]. Progress Report. Lung Cancer Mortality Among Underground Uranium. Miners With Low Lifetime Exposures To Radon Daughters. Proceedings of the Third NCI/EPA/NIOSH Collaborative Workshop: Progress on Joint Environmental and Occupational Cancer Studies:693-712.

A progress report was presented on a survey of lung cancer mortality in underground uranium (7440611) miners (SIC-1094) with low lifetime exposures to radon (10043922) daughters. The survey was an extension of an earlier United States Public Health Service (USPHS) survey. The cohort consisted of 3,362 white males and 780 American Navajo Indians who mined uranium on the Colorado Plateau between 1950 and 1963. The USPHS survey found elevated standardized mortality ratios (SMR) in white miners of 482 for lung cancer, 409 for tuberculosis, 331 for accidents, 324 for nonmalignant respiratory disease, and 262 for renal sclerosis. White miners had an all cause SMR of 158. The American Indian cohort members also had a significantly elevated risk of death from lung cancer, SMR 423. Risk of death from all causes was in deficit, SMR 86. The primary objective in continuing the study was to quantify lung cancer risk through 1982 according to radon daughter exposures. The authors note that vital status follow up from 1977 through 1982 will be accomplished using routine NIOSH methods. Exposures to radon daughters documented after 1969 will be added to the existing exposure records. Special attention will be given to lung cancer mortality risks for cohort members having lifetime exposures less than 120 working level months. A questionnaire has been developed to collect data in four areas: smoking history, occupational history, medical history, and a brief food frequency history. A total of 400 additional deaths among cohort members has been discovered.

Archer-VE; Gillam-JD; Wagoner-JK [1976]. Respiratory Disease Mortality Among Uranium Miners. Annals of the New York Academy of Sciences 271:280-293.

Respiratory disease mortality among uranium (7440611) miners was investigated in a group of 3,366 white and 780 American Indian workers with 1 or more months of underground uranium employment. Detailed occupational and smoking histories were obtained by personal interview during the complete physical examination. An annual census was taken for updating this data. Death certificates were obtained for those deceased. Cumulative radon daughter exposure values were calculated for each miner through the period of investigation. Mortality comparisons between the non white male populations of Arizona and New Mexico and Indian miners and between the United States white male population and white miners were made. For Indian workers, there were 107 deaths observed, versus 123.9 expected. There were significant differences for all malignant neoplasms, 17 observed versus 9.9 expected, with the excess composed of deaths from respiratory malignancies, 11 observed versus 2.6 expected. There were significant decrements in observed white deaths from all heart disease in this group, 2 observed versus 19.2 expected, and vascular diseases, 1 observed versus 6.2 expected. Only 20 of the Indians smoked a pack of cigarettes per day or more. For white miners there were 745 deaths observed versus 512.5 expected. Significant increases were seen for all malignant neoplasms, 206 observed versus 93.9 expected, the excess being due to 144 deaths from respiratory malignancies versus 29.8 expected. There were 80 deaths from cirrhosis of the liver versus 24.9 expected, 140 accidental deaths versus 43.3 expected, the excess being largely non vehicular accidents. Exposure/response curves for bronchogenic cancer showed a clear relationship to cumulative exposure. Small cell undifferentiated cancer was predominant among smoking and nonsmoking miners. Respiratory malignancies were also increased among smokers; however, radiation dose/dependent response plots were also linear, although not so steep, among nonsmokers. The authors conclude that there is a significant excess of respiratory cancer among these uranium miners, which is elevated by cigarette smoking.

Ward-EM; Smith-AB; Thun-MJ; Hills-B [1984]. Health Hazard Evaluation Report No. HETA-82-361-1437, Kerr-McGee Nuclear Corporation, Grants, New Mexico. Hazard Evaluations and Technical Assistance Branch, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, Report No. HETA-82-361-1437:1-34.

A health hazard evaluation at Kerr/McGee Nuclear Corporation's uranium (7440611) mill (SIC-1094) in Grants, New Mexico was conducted in November, 1982. Evaluation was requested because of union concern about exposure and possible nephrotoxic effects of yellowcake, a concentrate of natural uranium, produced at the mill Personnel records, company environmental and personal monitoring, and urine uranium bioassay data were reviewed. A total of 269 of 1127 urine samples exceeded the Nuclear Regulatory Commission (NRC) lower action concentration of 15 micrograms per liter (microg/l) for uranium, and 104 samples exceeded the NRC upper action concentration of 30microg/l. Workers in the yellowcake drier and precipitation areas of the mill had mean urine uranium concentrations of 15 to 30microg/l. Duration of exposure to yellowcake was 1.5 to 7 years. The authors conclude that 23.9 percent of the urine uranium samples exceed the NRC lower action limit and 9.3 percent exceed the upper limit. Further medical evaluation at the facility is not warranted as the longest exposure to yellowcake was only 7 years. They recommend that Kerr/McGee use the NRC guidelines for assessing exposure. Emission sources in the drier and precipitation area should be identified and engineering controls installed to reduce the exposure.

West-R[1984]. Mining Surveillance Target Investigation. Vanadium. Division of Respiratory Disease Studies, NIOSH, U.S. U.S. Department of Health and Human Services:1-28.

A mining surveillance target investigation of vanadium (7440622) was conducted. The purpose of the study was to characterize the surface oxidation states of vanadium in ore samples. Thirteen bulk samples obtained from vanadium or uranium mines and mills were analyzed by inductively coupled plasma atomic emission spectrometry (AES) to determine possible metal interferences and bulk composition. The samples contained up to 8 to 9 percent vanadium and were free of metal interferences. After AES, three samples were investigated by electron spectroscopy for chemical analysis (ESCA) to determine surface oxidation states of vanadium. ESCA determined oxidation states by measuring chemical shifts in observed spectra. The chemical shifts occurred due to changes in the core binding energies and were related to changes in the oxidation state. The chemical shifts of the three samples indicated that the vanadium existed as vanadium (V) -oxide (1314621), a plus 5 oxidation state. The author notes that one sample was expected to be vanadium(V)-oxide. The other two, however, were expected to have lower oxidation states. Samples containing vanadium in oxidation states below plus 5 may be unstable.
Additional research on sampling and analysis of vanadium minerals and compounds is recommended.

Waxweiler-RJ; Archer-VE; Roscoe-RJ; Watanabe-A; Thun-MJ[1983]. Mortality Patterns Among A Retrospective Cohort Of Uranium Mill Workers. Proceedings of the Sixteenth Midyear Topical Meeting of the Health. Physics Society, Inhalation Toxicology Research Institute:428-435.

An epidemiologic study of health hazards associated with uranium (7440611) milling was performed. Personnel records of 2,002 males from seven uranium mills were selected for inclusion in a retrospective cohort. Cohort members worked at least 1 year in uranium milling and did not work in uranium mining. Risk of mortality within the cohort was analyzed from 1940 to 1977 using the modified life table system. Observed deaths among the cohort were compared with number of deaths expected based on US death rates specific for cause, age, race, sex, and calendar period. Results were reported as the Standardized Mortality Ratio (SMR). Mortality due to many causes, including stroke, cardiovascular disease, alcoholism, cirrhosis, and all malignant neoplasms, was well below that expected. No statistically significant excesses of any malignancies were observed. A hypothesis of excess risk of lung cancer was not supported. An SMR of 167 was observed for chronic and unspecified nephritis and renal sclerosis. Mortality caused by nonmalignant respiratory disease (NMR) was significantly elevated (SMR at 163). When analyzed by induction/latency period, the SMR for NMR was 278, based on 27 observed and 9.8 expected deaths after 20 years. There was also a 44 percent excess in deaths from accidents. When the risk of death from lymphatic malignancies was analyzed by duration of uranium mill employment, excess risk was limited to the induction/latency period beyond 20 years, with 6 deaths observed versus 2.6 expected. The authors conclude that uranium mining is associated with NMR; however, the data does not support any conclusions regarding the etiology of this hazard.

Holaday-DA [1972]. Unattached Radon Daughter Atoms and Radon Daughter Equilibrium Ratios in Uranium Mines. NIOSH, Cincinnati, Ohio, Contract-099-71-0002:1-10.

Uranium mines in Colorado and New Mexico were surveyed for airborne concentrations of radon (10043922) and radon daughters. A procedure for measuring individual daughters and the fraction of each existing as free atoms was developed and used for field monitoring. Samples were taken in working areas and particle counts were made. The data was analyzed to determine the ratio of radon to radon daughters as well as the ratios among the radon daughters. The ratios and the fractions of free atoms varied widely. The values of the fractions of free atoms were dependent on concentrations of daughter atoms and particles, residence time of the air and charge on the atom. In general, the fractions of free radon daughter-A atoms varied inversely with the particle count. Significant fractions of the B-daughter and C-daughter were present in the free state. The author concludes that since the radon to working level ratios have not changed much in years, using the ratio as the basis for estimating the relative biological hazards is just as uncertain now as then. The number of daughters present as free atoms indicate that lung radiation doses calculated using any of the lung models need reexamination.

Thun-MJ; Baker-DB; Smith-AB [1981]. Health Hazard Evaluation Report No. HETA-81-055-954, Cotter Corporation, Canon City, Colorado. Hazard Evaluation and Technical Assistance Branch, NIOSH, Cincinnati, Ohio:1-51.

A medical survey was conducted with workers exposed to uranium (7440611) and yellowcake at the Cotter Uranium Mill (SIC-1094), in Canon City, Colorado, on November 12 to 14, December 15 to 17, 1980, and February 17 to 19, 1981. The Oil, Chemical and Atomic Workers International Union and its Local 2-844 requested the evaluation after reviewing biological monitoring data indicating excessive exposures at the mill. The medical study revealed that excretion of beta-2-microglobulin was significantly higher in the urine of uranium workers compared with comparisons. Beta-2-microglobulin excretion was significantly correlated with years of work in the yellowcake mill area. No clear evidence of impaired glomerular function was evident in the uranium workers. The authors conclude that a health hazard from overexposure to yellowcake at the old mill of this facility existed. They recommended that although exposures have been substantially reduced since 1979, environmental monitoring procedures should be established, additional medical epidemiological studies should be conducted.

Rodgers-JC [1972]. Radon Progeny Exposure Measurement Using Lead-210 New Mexico Environmental Improvement Agency, Radiation Protection Section, Santa Fe, New Mexico, NIOSH Contract No. 099-71-0012:1-110.

The feasibility of using lead-210 (14255040) as a quantative indicator of exposure to radiation in uranium mine atmospheres is studied. The nature of radon-222 is described, along with the principal inhalation exposure situation in a mine and the most widely used method for measuring the exposure. Four mathematical models predicting lead-210 ingrowth in a tunnel atmosphere from the decay of radon progeny in the air are described, and theoretical results are summarized. An extraction technique for the sample preparation for liquid scintillation counting of lead-210 is described, and an interlaboratory comparison check of dithizone extraction techniques applied to environmental samples is summarized. Field studies of the extent of background contributions to lead-210 samples, along with experimental studies of lead-210 ingrowth patterns, are summarized. The author concludes that a technique to enable the efficient extraction of lead-210 within the quantitative detection limit of the liquid scintillation counting system was developed. The measurement results indicate that the magnitude of the background contribution to the samples are the dominant source of lead-210. However, the lead-210 bioassay technique does not identify the extent of background contributions to the miner's body burden of lead-210.

Archer-VE; Gillam-JD; James-LA[1978]. Radiation, Smoking and Height Relationships to Lung Cancer in Uranium Miners. Proceedings of the Third International Symposium on Detection of Cancer, April 26-30, 1976, New York, H. E. Nieburgs Editor, Marcel Dekker, Inc., New York:1689-1712.

A prospective mortality study of 3366 white underground uranium (7440611) miners with 1 month or more underground employment before January 1, 1974, and 1231 surface workers with 1 month or less underground uranium mine employment, was conducted through September 1974 to determine radiation, smoking, and weight relationships to lung cancer. Radiation exposure responses varied with worker height, cigarette smoking and latent period. Radiation was more important than height, free silica (7631869) or cigarette smoking. Underground worker respiratory cancer rates were 4.9 times greater than expected from general population data, and 6.0 times greater than surface worker rate. Underground worker bronchogenic cancer rate was 6.5 times higher than amount the general population and among controls. Underground worker death rate from other respiratory diseases was 5.0 times greater than the general population and 1.7 times greater than the control. Underground workers had a much higher work related accidental death rate than did the general population or controls. Cigarette smokers had more benign and malignant lung disease than nonsmokers. Small miners had more lung disease than large miners. Results suggest that short miners receive higher noxious agent dosage than tall miners per lung tissue unit when doing equal work. It was concluded that airborne noxious agents' standards should consider amount of physical labor involved, and individual workers' sizes.

Lundin-FE; Wagoner-JK; Archer-VE[1971]. Radon Daughter Exposure and Respiratory Cancer Quantitative and Temporal Aspects. NIOSH-National Institute of Environmental Health Sciences Joint Monograph No. 1, NIOSH, Cincinnati, Ohio:1-193.

Epidemiologic and pathologic data on radon (10043922) daughter exposure and respiratory cancer among uranium (7740611) miners were evaluated. A statistically significant excess of respiratory cancer was identified among white uranium miners at each cumulative radiation exposure category down to and including the range of 120 to 359 working level months (WLM). Increased mortality from respiratory cancer and a dose relationship was indicated among uranium miners with or without other hard rock mining experience. Statistical analysis of respiratory cancer among workers in the potash (584087) industry and Indians in the southwest United States indicated that factors other than radiation were not responsible for the excess malignancies. A significant excess of small cell undifferentiated type tumors among uranium miners with respiratory cancer indicated a causal role of airborne radiation. This cell type was shown to increase with increasing cumulative radiation exposure. Animal studies indicated that the lung is relatively radiosensitive from the standpoint of carcinogenesis and that lung cancer may occur after exposure to 100 rads (ionizing absorbed dose of radiation). The risk of respiratory cancer per unit of exposure appeared to be greater in lower cumulative radiation groups than in higher ones. The authors conclude that a reduction in the federal standard for radon daughter exposure from 12 to 4 WLM per year may not yield the same proportionate reduction in respiratory cancer that would be expected from a linear relationship.

Pearson-JS [1975]. Analysis of the Reduction of Hazardous Radiation in Uranium Mines. NIOSH, Salt Lake City, Utah, HEW Publication No. (NIOSH) 75-171:1-144.

A report on the responses of companies, unions and government enforcement agencies to the problem of excessive radiation in uranium mines resulting in respiratory cancer in Colorado chiefly between 1950 and 1959, focusing on the organizational actions which ultimately solved the hazard and the non-technological factors that prevent an earlier solution of the problem. The greatest reduction in hazardous radiation in mines followed inspection and sanction activities by an enforcement agency. Results indicate the need for policies related to health and job safety that emphasize periodic inspections which carry a threat of punishment for employers who knowingly violate standards.

Holaday-DA [1974]. Evaluation and Control of Radon Daughter Hazards in Uranium Mines. Superintendent of Documents, U.S. Government Printing Office, HEW Publication No. NIOSH 75-117:1-68.

Health hazards which are produced by exposure to ionizing radiation are discussed. Emphasis is put on areas of evaluation of exposures to the radioactive gas radon-222 and its short-lived transformation products, and on methods of controlling such exposures. A limited discussion of the biological effects of radon and radon daughters is undertaken, and some procedures are given for evaluating hazards created by other common contaminants of mine atmospheres. The study endeavored to assemble pertinent information and make it available to those who are concerned with producing uranium at minimal risks. Where they were available, a variety of procedures for evaluating hazards are given, and examples of systems for controlling hazards are included.

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