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OCR for page 489
APPENDIX V
Nonmalignant Respiratory and Other
Diseases Among Miners Exposed to Radon
Epidemiological evidence on radon progeny as a potential risk factor
for nonmalignant respiratory diseases is restricted to uranium miners. As
discussed in Appendix III, animal studies are consistent with an associ-
ation between exposure to radon progeny and nonmalignant respiratory
diseases. Animals so exposed develop emphysema and interstitial fibro-
sis. Pulmonary fibrosis and, to a lesser extent, emphysema are common
findings in hamsters, rats, and dogs exposed to radon progeny alone and
in mixtures with uranium-ore dust.7-9 t~ These effects are not produced
to any appreciable extent in groups of animals until exposures to radon
daughters exceed several thousand working-level months (WLM). Thus,
the clinical diseases of interest are chronic obstructive pulmonary disease,
in which airflow obstruction results from emphysema and airway changes,
and interstitial processes such as pulmonary fibrosis.
The occurrence of nonmalignant respiratory diseases has been exam-
ined in miners from the Colorado Plateau region and from Ontario, Canada.
Several reports from the U.S. Public Health Service study described excess
mortality from nonmalignant respiratory diseases.4 26 Between 1950 and
1977, a fivefold excess of death occurred from nonmalignant respiratory
diseases, exclusive of tuberculosis, bronchitis, influenza, and pneumonia.26
Causes of death were primarily emphysema, fibrosis, and silicosis. The
effects of cigarette smoking were not considered.
In the Ontario miners, mortality from influenza, pneumonia, bron-
chitis, and asthma was not increased. However, mortality from silicosis
and chronic interstitial pneumonia was significantly elevated (11 deaths
observed, with 2.14 expected).
489
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490
HEALTH RISKS OF RADON AND OTHER ALPHA-EMITTERS
As part of the U.S. Public Health Service study of Colorado Plateau
miners, physical examinations and lung function testing were performed
in 1957 and 1960.2 Data were collected for 2,349 white males, but only
277 participated in both years. Spirometry was carried out at both exam-
inations, and the peak expiratory flow rate was measured in 1960. Three
different measures of radiation exposure were used: (1) years of under-
ground uranium mining, (2) a radiation index based on the working level
at the time of examination, and (3) a cumulative, ordinal measure of expo-
sure. The analyses were interpreted as showing loss of ventilatory function
with increasing cumulative exposure. However, the data were neither col-
lected nor analyzed with techniques that are currently accepted for lung
function parameters. Further, the accuracy of the exposure measures that
were used is uncertain.
In a later paper, Archer et al.3 used the same U.S. Public Health Ser-
vice study data and demonstrated an increasing prevalence of emphysema,
as diagnosed by a physician's examination, with increasing WLM. How-
ever, the diagnosis of emphysema, a histopathologically identified disease,
cannot be established by physical examination. Knapp et al.23 performed
more detailed studies on Colorado Plateau uranium miners and found ev-
idence of pulmonary dysfunction, both restrictive and obstructive. The
design of the investigation did not permit assessment of exposure-response
relationships with lung function measures.
More recently, Samet et al.20 surveyed 192 long-term New Mexico
uranium miners. The survey procedures included spirometry, completion
of a respiratory symptoms questionnaire, physical examination of the chest,
and interpretation of chest x rays. Total duration of underground uranium
mining, not WLM, was used as the exposure index. The design of the
investigation did not permit assessment of the effects of each potentially
hazardous agents as radon daughters, silica, and diesel exhaust. With
linear multiple-regression analysis that controlled for cigarette smoking,
duration of mining was associated with reduction of the forced expiratory
volume in 1 s and reduction of the midmaximum expiratory flow rate, but
not with reduction of the forced vital capacity. Chest x-ray abnormalities
compatible with silicosis were found in 9% of the uranium miners examined
for this survey.
These investigations have not separated the effects of radon-daughter
exposure from those of other atmospheric contaminants, such as silica,
diesel-engine exhaust, and blasting fumes, found in a uranium mine. Given
the inadequacies of available exposure data, epidemiological methods can-
not assess the individual contributions of all harmful agents to which
uranium miners are exposed or are potentially exposed.
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NONMALIGNANT RESPIRATORY AND OTHER DISEASES
OTHER DISEASES AMONG MINERS EXPOSED TO
RADON PROGENY
491
Mortality from selected causes among miners exposed to radon daugh-
ters Is detailed in Appendix IV, Table IV-16. In addition to the excess
risk from lung cancer, a number of the mining cohorts have experienced
an excess rick of mortality due to tuberculosis and to Other nonmalignant
respiratory diseases, (ICD Code 510-527, 7th revision). Because of the
past levels of silica in the mine atmospheres, most of these excesses are
believed to be due, in fact, to silicosis, which has been often diagnosed
on death certificates as silicotuberculosis, tuberculosis, or other forms of
nonmalignant respiratory disease.
Results from many studies of the mining populations have suggested
that there is a slight excess risk of stomach cancer, which has an el-
evated incidence among other mining groups, including gold miners in
Ontario without uranium mining experienced and coal miners in the
United States. Among the Ontario uranium miners, no excess risk ex-
isted for those without prior gold mining experience (9 observed versus
9.55 expected).~7 The cases are few, and the risks are low in most studies,
but the occurrence of this excess risk in eight different mining populations
lends credibility to the causation hypothesis that the excess has resulted
from a common occupational risk factor. From the reported analyses,
however, it is difficult to determine if that risk factor is radon progeny
because exposure-response analyses have not been reported.
Two studies, both based on small numbers, have found nonsignificant
excesses of skin cancer. While Sevcova et al.2i found that basal cell
carcinomas predominated, four of the five miners in the Colorado Plateau
study who died of skin cancer had melanomas.26 Since the other mortality
studies have not shown any significant skin-cancer excess, it is unlikely that
alpha radiation in the mines accounted for these excesses. However, the
occurrence of skin cancers, particularly nonmelanomas, cannot readily be
evaluated with a mortality study. Most skin cancers other than malignant
melanoma can be readily cured and rarely lead to death. No other sites
of malignancy appear to be consistently elevated among these mining
populations. Despite the fact that airborne radon daughters deposit in the
nasal passages, no cases of nasal cancer have been reported in any of the
epidemiological studies. Only Muller et al.~7 reported an expected value
of 0.8 for nasal cancer mortality among all Ontario uranium miners.
Excess risk of mortality due to nonmalignant renal disease was found
in a recent analysis of the Colorado Plateau study.26 In that survey,
chronic and unspecified nephritis was particularly elevated after 10 yr
latency (7 observed versus 1.9 expected; standardized mortality ratio,
362~. The committee considered that this excess may be either a chance
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492
HEALTH RISKS OF RADON AND OTHER AWHA-EAiITTERS
finding or indicative of an occupational risk factor, possibly alpha radiation
or uranium. The nephrotoxicity of soluble uranium in animals is well
documented in the experimental literature,24 but most of the uranium in
mines occurs as less soluble oxides.
Findings from relevant animal experunents should also be consid-
ered in interpreting the epidemiological data. In radon-daughter-exposed
animals, lesions observed in organs other than the lung are considered
spontaneous, or only indirectly exposure-related, in contrast to the case
for most alpha-emitters, which translocate Tom the lung to irradiate other
organs. Because of the extremely short half-life of the radon daughters,
their alpha emissions occur before they move to other organs. In animals
exposed to high concentrations of uranium-ore dust alone (and presumably
to radon daughters and uranium-ore dust mixtures) sufficient long-lived
radioactivity from the precursors of radon can concentrate in the kid-
neys to impair their function. However, direct evidence of renal function
impairment from exposure to radon daughters alone is lacking.
GYTOGENETIC STUDIES
The frequency of chromosome aberrations in blood cells has been ex-
amined in uranium miners and other underground workers as a marker
of injury due to ionizing radiation. Brandom and colleagues have re-
ported on chromosome aberrations in uranium miners from the Colorado
Plateau region of the United States. In their 1972 report,5 cytogenetic
abnormalities in peripheral lymphocytes from 15 miners were compared
with the findings in 15 age-matched nonminer controls; 5 of the miners
had lung cancer at the time of the study. Most of the aberrations were
more prevalent in the miners, and many of the differences between the two
groups attained statistical significance.
A subsequent report by Brandom et al.6 included 80 underground
uranium miners and 20 controls, frequency-matched for age and smoking
habits. Again, the various types of chromo~omal aberrations were more
prevalent in the uranium miners than in the controls. Exposure-response
relationships were evident up to a cumulative exposure of 3,000 WLM;
however, chromosonal abnormalities were less frequent in those with greater
than 3,000 WLM than in those with 1,74~2,890 WLM, the next lowest
exposure category.
Badgastein is a spa in Austria with thermal springs that discharge
water with a high concentration of radon. At Badgastein, patients are also
treated in a former gold mine that has a mean radon concentration of 3,000
psi/liter. Pohl-Ruling and Fischer evaluated cytogenetic abnormalities
in inhabitants of the community, bath attendants, and personnel exposed
underground. The investigators estimated blood doses from alpha and
OCR for page 493
NONMALIGNANT RESPIRATORY AND OTHER DISEASES
493
gamma radiation and used the dose estimates for assessing dose-response
relationships. The analyses did not provide a clear estimate of the effect
of alpha radiation, though they concluded that occupational alpha doses
flattened the dose-response relationships for radiation.
Relevant data are also provided by a study of cytogenetic abnormalities
in persons presumed to be exposed to high concentrations of radon in
household water.22 Chromosome aberrations were evaluated in 18 exposed
persons and 9 controls. Dicentrics, chromosome breaks, and cells with
chromosome change were significantly more frequent in the 18 exposed
subjects. However, exposures to radon daughters were not estimated, and
the suitability of the control group was not satisfactorily established.
To date, only the above-mentioned limited data are available on
cytogenetic abnormalities in radon-daughter-exposed populations. The
study of Colorado Plateau uranium miners indicates exposure-response
relationships for chromosome aberrations. However, confirming evidence
is not available from other populations, and the biological significance of
these observations has not been established.
EFFECTS ON REPRODUCTIVE OUTCOME
Recent and primarily descriptive data have renewed speculation that
uranium mining is associated with adverse reproductive outcomes. Muller
and colleagues~3~4~6 made the first reports on this subject in a series of
papers on Czechoslovakian uranium miners that were published during the
1960s. For 1,000 underground male workers, the numbers of children in
relationship to age did not deviate from that expected from nationwide
data.~3 However, in this sample and in another with 415 uranium miners,
the secondary sex ratio (male to female births) declined following the start
of underground employment from 1.08 to 0.85 in the former sample and
from 1.18 to 0.99 in the latter.
Potential reproductive effects of uranium mining received little further
evaluation until the early 1980s. At that time, descriptive datafrom New
Mexico were interpreted as suggesting the adverse reproductive effects
caused by uranium mining, by affecting either uranium miners or those
living in the vicinity of mines and mills.27
This more recent interest in reproductive effects caused by uranium
mining followed reports of high rates of congenital malformations and spon-
taneous abortion at the Shiprock Indian Health Service Hospital, located
in San Juan County, New Mexico, which serves Navajos in the north-
eastern portion of the Navajo nation. Goodman subsequently examined
the secondary sex ratio in New Mexico and Navajo births. His analyses
showed a temporal decline in the secondary sex ratio for New Mexico,
in comparison with nationwide data, that occurred during the period of
OCR for page 494
494
HEALTH RISKS OF RADON AND OTHER ALPHA-EMITTERS
extensive uranium mining in the state. The decline in secondary sex ratio
was greatest for counties with mining activity; further, the Navajo Area
Indian Health Service units with the lowest sex ratios also encompassed
areas of mining. A preliminary study of Grants, New Mexico, area miners
also suggested effects on the secondary sex ratio, and a study of 11 min-
ers showed distribution of Y bodies in their semen different from that in
control populations.~°
Waxweiler and Roscoe25 reviewed the results of a 1965 questionnaire
survey of Colorado Plateau miners; overall, the secondary sex ratio did not
vary with cumulative WLM. When the participants were stratified at the
population's median age of 24, the secondary sex ratio was significantly
increased in the highest exposure category. This observation could not be
readily explained.~25
Two studies were implemented to follow-up on these hypothesis-
generating observations: a survey of reproductive outcomes in wives of
Navajo uranium miners and a case-control study of births at the Shiprock
Hospital. Wiese and Skipper28 have recently reported preliminary findings
of the survey of reproductive outcomes. Questionnaires were distributed
to uranium miners in the Grants, New Mexico, area and to potash miners
employed in the southeastern portion of New Mexico. The study nonula-
_ ~ ,
. . ~ . ~ . _
tenon included 491 uranium and 226 potash miners. The investigators did
not find significant differences between the two groups in the frequency
~ . . . . . . .
or ~ow-olrtn-we~gnt Infants, sex ratio, miscarriages, or infertility. Birth
weights were lower in children born after the men began underground
mining, but the effect was present only in those births after 1970, when
average exposures to radon daughters were lower in the mines. Findings
from the case-control study in Shiprock have not yet been reported. To
date, the evidence on the possible reproductive effects of uranium mining
is largely descriptive and preliminary. The studies of uranium miners do
not show a consistent and readily interpretable pattern of effect. The data
related to possible effects of the uranium mining industry on the general
population are fragmentary at present.
REFERENCES
1. Archer, V. E. 1981. Discussion of secondary sex ratio of first-born offspring of
U.S. uranium miners. In Birth Defects in the Four Corners Area, W. H. Wiese,
ed. Transcript of a meeting. Albuquerque, N.M.: University of New Mexico
School of Medicine.
2. Archer, V. E., H. P. Brinton, and J. K. Wagoner. 1964. Pulmonary function of
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Archer, V. E., J. K. Wagoner, and F. E. Lundin, Jr. 1973. Lung cancer among
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4. Archer, V. E., J. D. Gillam, and J. W. Wagoner. 1976. Respiratory disease
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495
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Representative terms from entire chapter:
radon daughters
