Hanford Congenital Malformation CaseControl Study
Description:
The purpose of the study was to investigate the association of
parental occupational exposure to low-level external whole-body
penetrating ionizing radiation and risk of congenital malformations in
their offspring. Cases and controls were ascertained from births in
two counties in southeastern Washington State, where the Hanford Site
has been a major employer. Twelve specific malformation types were
analyzed for evidence of association with employment of the parents at
Hanford and with occupational exposure to ionizing radiation. Two
defects, congenital dislocation of the hip and tracheoesophageal
fistula, showed statistically significant associations with employment
of the parents at Hanford, but not with parental radiation
exposure. Neural tube defects showed a significant association with
parental preconception exposure, on the basis of a small number of
cases. Eleven other defects, including Down syndrome, for which an
association with radiation was considered most likely, showed no
evidence of such an association. When all malformations were analyzed
as a group, there was no evidence of an association with employment of
the parents at Hanford, but the relation of parental exposure to
radiation before conception was in the positive direction. Given the
number of statistical tests conducted, some or all of the observed
positive correlations are likely to represent false positive
findings. In view of strong contradictory evidence, based on no
demonstrated effects in genetic studies of atomic bomb survivors in
Hiroshima and Nagasaki, it is unlikely that these correlations results
from a cause and effect association with parental radiation exposure.
The hfmcca02 data file set is comprised of five analytic files with
information on 672 malformation cases and 978 matched controls. The
first file (MALCCA_1) contains demographic data for the parents and
the reproductive history of the mother. The second file (MALCCA_2)
contains birth data for the infant. The third file (MALCCA_3) contains
malformation data for cases, and additional medical data for the
infant and mother. If the parents worked at Hanford prior to the
infant's date of birth, the fourth file (MALCCA_4) contains employment
data, and the fifth file (MALCCA_5) contains radiation exposure
data. There is one record in each file for each of the cases and
controls.
A unique feature of this study was the linking of quantitative
individual measurement of external radiation exposures of Hanford
employees and the disease outcome, congenital malformations. The
population at risk, from which cases and controls were ascertained,
consists of live births and fetal deaths occurring in three local
hospitals during 1957 through 1980, the study ending date. 146 fathers
and 48 mothers of the 672 cases were employed at Hanford prior to
conception. 22 mothers of cases were employed at Hanford during
gestation. 125 fathers and 28 mothers of the cases had positive
recorded doses prior to conception. Only 1 mother of a case received
more than 1 mSv during gestation. Information on internal radionuclide
depositions was also obtained. However, only 1 father of a case had
evidence of a deposition, and it was determined to be less than 1% of
the applicable maximum permissible body burden.
Radiation exposure data routinely collected at Hanford includes the
doses from external sources to the whole body, the skin of the whole
body, and the extremities, for each employee working with or near
radiation sources. Because exposure to the gonads was the primary
interest of this study, analyses were limited to consideration of
exposure to external whole-body penetrating radiation. Dose estimates,
presented in units of millisieverts, were obtained primarily from
personal dosimeter measurements. A sievert is numerically equivalent
to the absorbed dose in gray multiplied by a quality factor expressing
the biological effectiveness of the radiation type. Factors of 10 for
fast neutrons, 3 for slow neutrons and 1 for photons were used to
convert external exposure measurements to dose estimates. Workers who
are considered at risk for internal depositions also undergo routine
bioassays and in vivo tests to determine such radiation exposure.
Citations:
Sever, Lowell E., Ethel S. Gilbert, Nancy A. Hessol and James
M. McIntyre. 1988. "A Case-Control Study of Congenital Malformations
and Occupational Exposure to Low-Level Ionizing Radiation." American
Journal of Epidemiology 127:226-42.
Notes:
Dr. Lowell E. Sever was employed by the Pacific Northwest Laboratory
and the Centers for Disease Control during the course of this
study. He is currently employed by the Pacific Northwest Laboratory.
Earliest exposure: 12/31/1899
Latest exposure: 12/31/1899
Latest Followup: 12/31/1899
Contacts:
Principal Investigator: Lowell E. Sever, Phone (206) 528-3348, FAX
(206) 528-3553, email LE_Sever@pnl.gov
Principal contact: Jeff A. Buchanan, Phone (509) 376-4308, FAX (509)
376-4533 , email JA_buchanan@pnl@gov
Agencies performing study:
Division of Birth Defects and Developmental Disabilities Center for
Environmental Health, Centers for Disease Control, Atlanta, GA 30333
Hanford Environmental Health Foundation, P.O. Box 100 Richland, WA
99352 (509) 376-8500
Pacific Northwest Laboratory, P.O. Box 999 Richland, WA 99352 (509)
376-4308
Agency Funding Study:
Office of Health and
Environmental Research, U.S. Department of Energy