ML20003F870
| ML20003F870 | |
| Person / Time | |
|---|---|
| Issue date: | 01/29/1981 |
| From: | Minogue R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Rich Smith NRC OFFICE OF STANDARDS DEVELOPMENT |
| References | |
| RIL-112, NUDOCS 8104230789 | |
| Download: ML20003F870 (4) | |
Text
,
g e.
0, UNITED STATES NUCLEAR REGULATORY COMMisslON
'o j
WASHINGTON. D. C. 20555 y
y * ).c 'g E
g.'
% 8[
JAl. 2 31361 I
Ray G. Smith, Acting Director e
MEMORANDUM FOR:
Office of Standards Development Robert B. Minogue, Director
'j FROM:
Office of Nuclear Regulatory Research i.
112 - HEALTH RESEARCH INFORMATION LETTER #
SUBJECT:
STATUS AND BODY RADI0 ACTIVITY OF FORMER THORIUM WORKERS Summary _
The health effects of industrial exposure to thorium are being investiga In a study by studying the former employees of a thorium-processing plant.
cchert of 3039 men, there were 511 known deaths versus 486.8 deat on the basis of age-and year-specific mortality rates for U.S. white ma In general, differences between the observed and expected numbers from specific causes showed little association with measures of thoriumH exposure (job type and length of employment).
l d
tically significant excess of deaths from pancreatic cancer among men em a year or more (6 observed vs 1.3 expected) but not for shorter-(3 observed vs 2.7 expected).
a higher proportion of cigarette smokers relative to U.S. males, and t could explain at least part of the excess mortality from lun Medical examinations and respiratory diseases.
dents was found (38 observed vs 23.2 expected).
i measurements of residual body radioactivity are being made on a sub By thoron-breath measurements, thorium of 592 men most exposed to thorium.
deposition was detected in 13i of 194 men who have been examined, measurable amounts of bismuth-212 (range 0.2 to 3 nCi) were foun the men by gamma-ray measurements in vivo.
Introduction l for the project entitled, This memorandum transmits an interim report
" Health Effects of Industrial Exposure to Thorium The study is being conducted by the Center for l
Research Branch, endorsed by your office in RR-RES-77-3.
i 1 Health Status and Body Radioactivity of Former Thorium Workers, I'
NUREG/CR-1420, January 1980 B 10.4 230 %%
,- ~ ~ ~;"~
(
a Ray G. Smith JAN 2 91981 The interim report provides a sumary of the progress to date in the study of the health of former workers at an industrial plant where thorium and rare-eartn chemicals were produced from the 1930's to 1973. The objectives of the study are as follows:
(1) to assess possible health effects of employment in the thorium milling industry by comparing mortality experience and morbidity characteristics of former thorium workers with those of suitable control populations, (2) to examine mortality and morbidity outcomes by estimated exposure levels to thorium and daughters for possible dose-related effects, and (3) to determine the body distribution of inhaled thorium and rare-earths in humans by in vivo radioactivity measurements of the workers and by analysts of autopsy samples.
Methodoloay With the cooperation of the Kerr-McGee Chemical Corporation, empicyment lists of the former Lindsay Light Company were compiled from various records. A total of 4582 former employees were identified, but due to incomplete informa-tion, the study population was limited to 3222 men and 714 women who worked at the West Chicago site.
Information on working conditiens and exposure to radicactivity was obtained from a report on an industrial hygiene survey made in 1952 by the U.S. Atomic Energy Comission and from later AEC compliance inspections from 1956 to 1973.
Kerr-McGee also provided complete records of the personnel dosimeter readings and data sheets on survey meter readings and measurements of airborne and surface radioactivity.
In addition, many of the filter samples taken for measurement of airborne radioactivity have been obtained and are being analyzed.
Mortality Study Based on name, social security number, and date of birth, searches of Social Security Administration records were made to identify deceased workers. Copies of death certificates were obtained from state vital statistics offices and the cause of death coded.
Person-years of follow-up were enumerated from the year of first employment at the West Chicago plant, or from 1940 for those who had started work earlier, to the year of death or of last search by the Social Security Administration.
Standardized mortality ratios (SMR's) were calculated by dividing the observed number of deaths by the expected number of deaths calculated by tne method of Monson for each cause of death category.
M
(
,]
- g ; 9 3931 Ray G. Smith Morbidity Study Initially the subgroup for the morbidity study included only the 592 men who worxed at the West Chicago plant for at least one year in occupations involving A number of methods were used to the higbest probable exposure to thorium.
trace members of this group, and a questionnaire on medical history and The same questionnaire will be sent to respiratory symptoms was sent to them.
a random sample of the remaining 2630 men in order to obtain information on shorter-term workers and on men in other occupational groups.
Medical Examinations and Radioactivity Measurements Medical examinations and measurements of radioactivity are planned for those The general medical protocol still alive amcng the 592 men identified above.
includes a complete physical examinatien, blood and urine analyses, electro-cardiogram, visual and auditory examinations, chest X-ray, and pulmonary A detailed medical history will be obtained to amplify the function tests.
questionnaire reply.
The in vivo radioactivity measurements consist of external whole-body counting and Ellection of thoron in exhaled breath. Autopsy samples will be radio-chemically analy::ed to relate crgan content to the external measurements.
Results and Discussion Mortality Analyses 1
Based on the analysis of all 511 deaths among male workers, only two statisti-The observed l
cally significant results were found for U.S. white males.
number of deaths from diseases of the circulatory system was significantly lower than the expected number. The observed number of deaths from motor
},
vehicle accidents was significantly higher than the expected number.
Because a major addition to the plant was built in 1954 and licensing require-ments were imposed in 1956, the study population was divided into two cohorts based on year of first employment (1940-54 and 1955-69). The SMR for overall mortality was statistically significant for the later (1955-69) group but not Additionally, the later group showed statistically j
cI for the earlier group.
f significant SMR's for lung cancer and cancer of the pancreas.
Mortality from selected causes was analyzed by duration of employment:
f The shortest 0-1 month, 2-11 months, 12-35 months, and greater than 36 months.
tenn workers showed high SMR's for cancers of the rectum and lung, diseases of The second group showed no notably the respiratory system, and external causes. The mortality ratio was high for high mortality ratios except for pneumonia.
lymphosarcoma in the 12-35 month group and for leukemia in the greater than 36 months group; SMR's were high for cancer of the pancreas in both of these
- groups, i
.w q-(
a M 29 E Ray G. Smith Mortality from selected causes was also analyzed by job classification:
group 1 - laborer, operator; group 2 - maintenance; group 3 - service, G technical, office, other.
cancers combined, lung cancer, skin cancer, and motor vehicle accidents.
Four of five deaths due to leukemia occurred in group 1, but the SMR wasT not statistically significant.
The SMR for diseases of cancers of the pancreas but not for lung cancer.
the respiratory system was high in group 3.
Radioactivity Measuremer.ts The results of the whole-bedy counting showed statistically significant amounts The largest amount was estimated to of bismuth-212 in 55 of the 195 people.
be abcut 3.2 nCi of bismuth-212, which corresponds to 29 mg of thorium, assuming radioactive equilibrium and no losses.
In contrast to the above, many more workers (131) showed detectable amounts of thoron in their exhaled breath.
Future Work
_The results of the mortality study underscore the importance of the information Questionnaires have been returned by to be obtained from the morbidity study.
physical examinations 300 of the 356 men who were located while still living,and radioac eventually all remaining members of the sub-group will be examined.
Conclusions and Recomendations The observed higher mortality ratios involving cancer of the lung or pancreas in a few of the male thorium-workers suggest possible effects due to thorium Attribution is not straightforward because at least part or other chemicals.
of the lung cancer excess mortality could have been related to cigarette The findings were not consistent with a strong relationship between The results to smoking.
length of employment and mortality from respiratory disease.
date offer no evidence that present standards for occupational exposure to Any large excesses of deaths due to exposure thorium require modification.
The morbidity to thorium would have been detected by the mortality analyses.
analysis to be performed will provide a better understanding,of the small Additionally, increase in cancer incidence among the workers being studied.
the breath, bioassay and whole body radioactivity measurements will provide l
l much valuable information on thorium metabolism.
For further information on this research program, please contact Dr.' Judith Foulke, Environmental Effects Research Branch (427-4358).
hd 0 TWf j
Robert B. Minogue, D'irector l
Office of Nuclear Regulatory Research i
_