Worker Health Study Summaries

Research on long-term exposure

Uranium Millers (2)

2006

Study Background

Why did NIOSH study the Health Risks from Exposures in Uranium Mills?

The health of uranium workers has been of concern to health officials since 1950. In that year, the United States Public Health Service and the Uranium Industry began a long-range program designed to detect and control the hazards to the health of uranium workers.

Reports from the central European uranium mining area had indicated a high rate of lung cancer among uranium miners and uranium mill workers. Since the agent that caused the disease was unknown, the PHS included both uranium miners and millers in their initial evaluations.

Later, the PHS focused specifically on uranium miners since radon daughters found in mines were thought to be the main radiation problem. Results from these studies were published and uranium miners were notified of these results by NIOSH in 2000.

Other studies focused on the health risks among uranium millers. The primary exposures of interest in uranium mills were uranium, silica, and vanadium.

The 1973 U.S. Public Health Service Mortality Study of Uranium Millers

The PHS study of uranium millers included 662 men who worked in one of six different uranium mills. The PHS examined workers between 1950 and 1953. The exam consisted of a physical examination, chest x-ray, and blood and urine analyses. The PHS also collected occupational, medical, and social histories.

The PHS collected death certificates with causes of death for any deceased miller. During the period 1950 through 1967, the PHS observed 104 deaths. This was similar to the 105 deaths expected based on death rates for the white male population of the area.

Results from the study did reveal, however, an excess risk of death from blood cancers other than leukemia, even though the numbers were small. Only four deaths were observed, but only one death was expected.

The 1983 NIOSH Mortality Study of Uranium Millers

In 1983, NIOSH completed a much larger study of the health risks among uranium mill workers.

The study included 2,002 uranium millers employed in any one of seven mills for at least one year before 1972.

The results showed again that deaths due to blood cancers were higher than expected among those workers first employed in the mills 20 years earlier.

The results also showed an increased risk of deaths due to non-malignant (non cancerous) lung diseases and accidents.

Chronic kidney disease was also higher than expected, but three of the six deaths were probably not associated with uranium mill exposures. Uranium mill employment was brief for all six cases.

The 2004 NIOSH Mortality Study of Uranium Millers – An Update

Due to continuing concern about the health risks of uranium milling, NIOSH conducted an update of the 1983 study.

Subjects

The 2004 study included 1,484 men. To be included in the study, the workers had to have:

• worked in one of seven uranium mills;
• worked for at least one year in the mills, and at least one day after January 1, 1940;
• never worked in underground or above ground uranium mines.

Records Used

To conduct the study the following were used:

• personnel records from the companies, which included an individual’s work time in the mill;
• records of end-stage renal disease obtained from Medicare. End-stage renal disease is the most serious form of kidney disease, when the kidneys no longer work;
• certificates of death.

Death Rates

First we calculated the expected number of deaths using U.S. death rates.

Then we compared the observed (actual) number of deaths among the uranium mill workers in the study to the expected number of deaths.

If the observed number of deaths for any disease is higher among uranium mill workers, this may have been due to working in uranium mills.

We also calculated the expected number of end-stage renal disease cases (not deaths). We then compared these expected numbers with the observed cases of end-stage renal disease.

What were the 2004 NIOSH Mortality Study Results?

Non-Malignant Respiratory Diseases

The 2004 study found an increased risk for non-malignant lung diseases. We expected 70 deaths and observed 100. This category included emphysema, pneumoconiosis, and other lung diseases. (Pneumoconiosis is a type of lung disease caused by breathing in mineral dust.)

Lung cancer

Deaths from lung cancer were higher than expected. We expected 69 deaths and found 78.

Blood cancers (other than leukemia)

We found a higher than expected risk for blood cancers (other than leukemia). This category includes lymphoma and Hodgkin’s disease. We expected 11 deaths and observed 16.

Kidney Disease

We found a slightly higher than expected risk in deaths for chronic renal disease. We expected 6 deaths and observed 8.

The number of end-stage renal disease (ESRD) cases was fewer than expected.

Mortality by Length of Employment

It should be noted that the risk of death from the above diseases was not higher among workers who were employed for the greatest number of years. This means that some reason other than working in the mills may have been the reason for the above increase in deaths.

Mortality by Date of Hire

The risk of death was higher for emphysema and lung cancer among men hired before 1955. This may have been due to exposures to uranium, silica, and vanadium dusts that were probably higher prior to 1955.

For the category, pneumoconiosis and other lung diseases, results were similar prior to and after 1955.

Conclusions

The study found an increased risk for various causes of death among millers, but was unable to show conclusively that these deaths resulted from working in the mills.

The study results evaluated workers as a group. The results do not mean that all uranium millers will acquire one of these diseases.

Limitations of the Findings

The interpretation of the study findings was limited by the following:

We could not estimate individual exposures to uranium, silica, and vanadium.

The number of workers in the study was somewhat small, thus making it difficult to detect excess risks especially for end-stage renal disease and other rare causes of death.

We did not have information on the smoking habits among millers. Smoking may affect the risk for many diseases, especially respiratory diseases.

More Information

Study Reports

Pinkerton LE, Bloom TF, Hein MJ, Ward EM. Mortality among a cohort of uranium mill workers: an update. Occup Environ Med 2004;61:57-64.

Waxweiler RJ, Archer VE, Roscoe RJ, et al. Mortality patterns among a retrospective cohort of uranium mill workers. In: Epidemiology Applied to Health Physics, Proceedings of the Sixteenth Midyear Topical Meeting of the Health Physics Society, Albuquerque, New Mexico, January 9-13, 1983;428-435.

Archer VE, Wagoner JK, Lundin FE. Cancer mortality among uranium mill workers. J Occup Med 1973;15:1,11-14.

Printer Friendly Documents with Information Related to the Studies

The following documents contain information related to the studies, and are in PDF format for easy printing. Viewing these documents require Adobe Corporation’s free Acrobat Reader, available here.

A Study Overview – Health Risks from Exposures in Uranium Mills
This fact sheet presents a brief summary, in bullet format, of the purpose, design, results, conclusions, and limitations of the 2004 NIOSH study of uranium millers.

Information About Certain Diseases Regarding Uranium Millers
This fact sheet presents a description of the diseases that were mentioned in the 2004 NIOSH study of uranium millers along with their symptoms. Also included are contacts where one can obtain additional information regarding these diseases.

Radiation Exposure Compensation Act (RECA)
The Radiation Exposure Compensation Act (RECA) gives eligible millers (or their next-of-kin) compensation for certain diseases due to their employment. The fact sheet presents information regarding how to qualify and whom to contact.

Questions Or Comments?

If you have any questions or comments, would like more information, or would like a copy of any of the study reports:

Call our NIOSH toll-free 800 number: 800-356-4674. Say you are calling about the Uranium Millers Notification.

e-mail questions, comments, or suggestions to: nioshworkernotification@cdc.gov

For other NIOSH publications:

NIOSH Publications
4676 Columbia Parkway
Cincinnati, OH 45226-1996
Phone: 800-356-4674
Fax: 513-533-8573
E-mail: pubstaft@cdc.gov
Web site: www.cdc.gov/niosh