Summary of Results of the U.S. Commercial Nuclear Plant Worker IARCStudy

[John_Sukosky@DOM.COM]

FAQ'S

United States Commercial Nuclear Power Plant Worker

Cancer Mortality Study Report,

part of the

Ongoing Collaborative Cancer Mortality Study

Conducted by the

International Agency for Research on Cancer (IARC)



IARC Study manuscript published in Radiation Research November 1, 2004:

Howe, G. R., Zablotska, L. B., Fix, J. J., Engel, J., and Buchanan, J.,

Radiation Research 162, 000-000(2004), Analysis of the Mortality Experience

amongst U.S. Nuclear Power Industry Workers after Chronic Low-Dose Exposure

to Ionizing Radiation



The cohort studied consisted of 53,698 workers who were followed for up to

18 years between 1979 and 1997.  The mean total cumulative equivalent dose

for the whole cohort was 25.7 millisievert (i.e., an average of 2.57 rem

career dose for the study period).



Comparison of mortality rates of the cohort members to the gender, age,

calendar year, and cause-specific U.S. population mortality rates showed

that they were considerably lower (60 percent lower for all-cause

mortality, 35 percent lower for all cancers, and 66 percent lower for all

non-cancer mortality, including deaths from heart, respiratory and

circulatory system disease).



The workers included in the study exhibited a very substantial healthy

worker effect, i.e., there were considerably lower cancer and noncancer

mortality rates than the general population.



Internal comparisons within the cohort were made to quantify the

relationship between risk of cancer and radiation dose.  Positive, though

statistically non-significant, associations were seen for mortality from

leukemia (excluding chronic lymphocytic leukemia) and all solid cancers

combined.  These estimates were very similar to those extrapolated from the

study of the Japanese Atomic Bomb survivors.



The researchers reported a strong positive and statistically significant

association between radiation dose and death from arteriosclerotic heart

disease, including coronary heart disease.  The authors of the study noted,

however, that this association is stronger than that found in other studies

and cautioned that the "somewhat contradictory results suggest cautious

interpretation of these observations."  They suggested that this finding

merits further investigation.



Current radiation dose limits for workers are based on cancer risk

estimates obtained by extrapolating data from epidemiological studies of

individuals exposed on average to much higher doses at higher dose-rates,

such as the survivors of the atomic bombings in Japan.  This study of U.S.

commercial nuclear workers is an important contribution to the

understanding of these risks, since it allows a direct estimate of the

risks from low doses of radiation and allows a comparison to risks

extrapolated from the higher-dose studies.



Overall, the researchers noted that the study's strengths included the

availability of several sources of dose records, the precise estimates of

these doses, and the "sizable" cohort.  The study's most significant

limitation, on the other hand, was a "lack of statistical power" due to the

relatively low doses of radiation involved and wide "confidence intervals"

of the risk estimate.



This cohort is still relatively young (mean age at end of follow-up is 45

years) which explains the small number of deaths.  Further follow-up and

the inclusion of the present data in an ongoing





John M. Sukosky, CHP

Dominion

Surry Power Station

(757)-365-2594 (Tieline: 8-798-2594)



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