Health Risks of Ionizing Radiation: - Clark University

11
NUCLEAR POWER ACCIDENTS
The two nuclear power accidents eligible for this
review are not the only two in human history, but they
are the only two with substantial epidemiological
analysis of health outcomes in surrounding
populations. The Three Mile Island (TMI) accident
in Pennsylvania was relatively low-level, although
it was the largest accidental release of radiation
from a commercial power facility in the US, but
the Chernobyl accident was a major catastrophe.
This section begins with a short review of the TMI
accident and goes on to explore in some depth the
follow-up of the effects of Chernobyl.
11.1 Three Mile Island
The partial meltdown at TMI on March 28, 1979
released several million curies of xenon and iodine
isotopes into the air. The average whole-body
gamma dose for a person within 5 miles of TMI was
estimated to be about 0.1 mSv (Hatch, et al. 1990;
Talbott, et al. 2000; see Figure 11-1). This amount
of radiation is low, and detecting risks at this level is
not likely using standard epidemiological methods.
On the other hand, there were problems with dose
estimation, including legal restrictions on how the
doses could be estimated and missing data for critical
periods immediately after the accident (Wing et al.
1997). Based on the official dose estimates, an early
report from a President’s Commission concluded
that the only possible health impact would be mental
distress 1 , but several cancer outcomes appear to have
been elevated as described below.
Hatch et al. (1990) analyzed cancer incidence
according to levels of dose, comparing incidence
among those in the highest quartile to incidence
among those in the lowest quartile 2 . Incidence
was further broken down in according to years of
observation. 1975-1979 was the pre-accident period;
1981-1985 and 1984-1985 are periods defined
according to the assumed latency of various cancers
(2 or 5 years). Non-Hodgkin’s lymphoma and lung
Figure 11-1. Radiation emissions and incidence of lung
cancer, 1981-1985, in the TMI 10-mile area (http://ehp.niehs.
nih.gov/members/2003/6200/6200.html#accci).
1 JG Kemeny et al. 1979. Report of the President’s Commission on the Accident at Three Mile Island – The Need for
Change: The Legacy at TMI. ISBN 0-93578-003. Washington, DC: Govt. Printing Office.
2 Dividing a group into quartiles means creating four groups; the lowest 25% of dose, the highest 25% of doses, and
two groups in the middle (25-50% and 50-75%).
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