CA: A Cancer Journal for Clinicians, Vol 48, Issue 5 285-298, Copyright © 1998 by American Cancer Society
Perspective: National Cancer Institute summary report about estimated exposures and thyroid doses received from iodine 131 in fallout after Nevada atmospheric nuclear bomb tests
S. A. Hundahl
Queens Medical Center, Honolulu, HI, USA.
Environmental 131I contamination from atmospheric nuclear bomb tests
conducted at the NTS from 1951 to 1958 exposed Americans nationwide to a
cumulative average dose of 1 to 4 rad to the thyroid gland. By comparison,
10 years of exposure to natural background sources of thyroid radiation
results in a cumulative dose of 1 rad. Americans living in certain
high-deposition areas received an average cumulative thyroid dose of as
much as 16 rad. Individual dose rates vary considerably as a function of
age at the time of exposure, site of residence, and dietary habits with
respect to milk consumption. The individual cumulative thyroid dose for
persons born between 1945 and 1958 may be significantly higher than the
reported averages for their locale. The NCI report contains voluminous data
tables permitting detailed calculations of individual dose. Additionally,
color-coded dose maps allow one to approximate individual dose
conveniently. Translation of cumulative thyroid dose attributable to 131I
to predictions of increased rates of thyroid cancer appears problematic and
is the subject of further study. In contrast to studies of patients
receiving external thyroid irradiation, existing studies of patients
treated with 131I for diagnostic and therapeutic medical purposes do not
document increased rates of thyroid cancer. An Institute of Medicine task
force is expected to issue a report on this subject in September 1998. This
review also briefly summarizes the evaluation, diagnosis, and treatment of
patients with papillary and follicular thyroid cancers. Data from 53,856
patients with thyroid cancer accessioned to the NCDB from 1985 to 1995
document extremely high survival rates for patients in the United States
with papillary and follicular thyroid cancer.