Re: New Steve Wing Study

[steve.epperson@srs.gov]

     The following is a summary of the Steve Wing Study that was 
     distributed through our employee communications.
     
     
     Steve Epperson
     Savannah River Site
     standard disclaimers apply
     
     
     
     
     
     Epidemiology of Multiple Myeloma at Four DOE Sites
     
     Department of Epidemiology
     
     University of North Carolina at Chapel Hill
     
     
          An epidemiological study of multiple myeloma among Department of 
     Energy (DOE) workers.  Multiple myeloma is a cancer of the 
     blood-forming tissues, affects primarily older people, and is often 
     fatal.  The study, which began in October of 1993, consisted of a 
     feasibility phase, a protocol development phase, and a implementation 
     phase.  The final report was submitted to the funding agency, the 
     National Institute for Occupational Safety and Health (NIOSH), in 
     March of 1997.
     Ionizing radiation is an accepted cause of multiple myeloma and most 
     other types of cancer.  This study was requested by NIOSH because of 
     previous reports of associations of multiple myeloma with radiation 
     exposures of workers at the Hanford site.  The new study was intended 
     to include more cases of the disease, better evaluation of radiation 
     doses, and measurement of other occupational exposures not available 
     in the Hanford studies.
          Facilities were chosen for inclusion in the study based on their 
     age, size, type of operations, and availability of basic records 
     assembled for past epidemiological studies.  Those records included 
     employee rosters and information on causes of death.  These data 
     formed the basis for choosing cases - workers who died with multiple 
     myeloma - and a random sample of controls who lived to be as old as 
     the cases.  Because multiple myeloma is rare, four facilities were 
     chosen in order to identify a sufficient number of cases for 
     statistical analysis. 
          We identified 98 multiple myeloma deaths and 391 age-matched 
     controls from a combined roster of 115,143 workers hired before 1979 
     at Hanford, Los Alamos National Laboratory, Oak Ridge National 
     Laboratory, and the Savannah River site, and followed for vital status 
     through 1990 (1986 for Hanford).  Information on prior work history, 
     smoking, medical x-rays, and exposure to physical and chemical agents 
     was derived from personnel, medical, industrial hygiene and health 
     physics records.
          The study compared exposure histories of cases and controls to 
     investigate whether certain occupational exposures were relatively 
     more common among cases.  Results of these comparisons were expressed 
     in terms of an epidemiological measure called the odds ratio.  The 
     odds ratio is an estimate of the ratio of the disease rate among 
     workers with a particular characteristic compared to those without the 
     characteristic.  An odds ratio of 1.0 indicates that disease 
     occurrence is the same among people with and without the 
     characteristic; an odds ratio of 2.0 would indicate that people with 
     the characteristic have twice the rate of disease as those without.  
     We also calculated a measure of the precision of the odds ratios 
     called the 95% confidence limit (95% CI).  This statistic is an 
     indication of the stability of the odds ratio.
          We attempted to determine whether workers had been exposed to a 
     variety of chemical and physical agents that might be causes of 
     multiple myeloma, including solvents, metals, welding fumes, asbestos, 
     ionizing and non-ionizing radiation.  With the exception of external 
     penetrating radiation, for which most longer term workers had at least 
     some badge data, information on exposures to specific chemical and 
     physical agents was not sufficient to assign a quantitative exposure 
     estimate or even to determine with a high degree of certainty whether 
     or not a worker was exposed.  We calculated odds ratios for many 
     factors although we believe that the results are not very 
     interpretable due to the poor measurement of exposures.  With the 
     exception of the estimated whole body dose from ionizing radiation, 
     other factors were not clearly in excess among cases compared to 
     controls.
          External penetrating ionizing radiation was measured by 
     individual dosimeters.  Whole body radiation dose was constructed by 
     adding annual external radiation doses and estimates of doses from 
     tritium.  Although tritium is an internal radiation exposure, it was 
     routinely counted with external dose because it irradiates the body 
     uniformly.  Neutral doses were included using quality factors employed 
     at the facilities, which varied from 8 to 20.  Tritium and neutrons 
     comprised only a small fraction of whole body dose estimates.
          Total cumulative radiation doses were similar between cases and 
     controls.  However, doses received at ages 45 and above were 
     associated with an average 7% per 10 mSv (one rem) increased risk of 
     multiple myeloma, adjusted for age, race, sex, facility, period of 
     hire, birth cohort, monitoring for internal radionuclide 
     contamination, and external radiation received prior to age 45.  The 
     95% confidence limit for this estimate was 1-13%.  For exposure at 
     ages 45 and above, the odds ratio for workers with cumulative doses of 
     50 mSv (5rem) or greater compared to workers with cumulative doses of 
     less than 10 mSv was 4.34 (95% CI 1.46-12.90).
          The association of multiple myeloma with radiation doses at older 
     ages is consistent with findings from some epidemiological studies of 
     cancer among workers and theoretical expectations that older people 
     are more sensitive to a variety of carcinogens.  These findings and 
     other studies of nuclear workers have implications for radiation 
     protection standards for workers and the general public.
     
     Address correspondence to:  Steve Wing, Department of Epidemiology, 
     CB# 7400, 
     School of Public Health, University of North Carolina, Chapel Hill, NC 
     27599-7400
     Telephone:  (919) 966-7416; FAX: (919) 966-2089; email:  
     steve_wing@unc.edu