ML19224B379
| ML19224B379 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/16/1979 |
| From: | Ellett W ENVIRONMENTAL PROTECTION AGENCY |
| To: | Hironori Peterson NRC OFFICE OF STANDARDS DEVELOPMENT |
| Shared Package | |
| ML19224B374 | List: |
| References | |
| TM-0507, TM-507, NUDOCS 7906150020 | |
| Download: ML19224B379 (5) | |
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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WASHINGTON. D.C.
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APR 161979 Mr. Harold T. Peterson, Jr.
Health Physicist Nuclear Regulatory Cc=missico 5650 Nicholson Lane, Room 209 Rockville, MD 20852
Dear Mr. Petersen:
As agreed in our phene discussica April 12, 1979, I am forwarding copies of the risk esti=ates made by BAB during the Three Mile Island Nuclear E=ergency.
'n using the risk estimates, please remember:
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Socatic and genetic risk coefficients are derived from the BEIR Report, p. 171.,
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The socatic risk esti=ates were derived frem a modified
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versica of the CAIRD co=puter code.
2he modificatico makes it possible to perform individual analysis of each cohort in an exposed g
population. Each cohort is followed until its extinction and all deaths fmm radiation exposure enumerated.
A weighted sum of the deaths from each of these analyses i& then calculated. The teights
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are determined by the age distribution of the exposed populatica at I
the time of exposure.
In this particular analysis, each individual in every cohort was assumed to receive a single one rem dose.
The total exposed population was assumed to be 100,000 persons and distributed in age like the 1970 U.S. population. Numbers therefore will rese=ble BEIR estimates but not be identical.
3 Estimates of thyroid risk were developed outside of BEIR estic.ates. The esti=ates are for 131I specifically and are about a facter of 10 lower than would be estimated for x-ray or some other (short half life) radiciodines.
We did not atte=pt to estimate risk to other specific crgans since there were no apparent crgan exposures as such.
Likewise, we did not attempt to esti= ate skin cancer risk because the variance of
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2 the risk estimate is so great that no realisti, esti= ate can be made at this time.
In addition, the uncertainty in incidence as compared to the risk of fatal skin cancer further complicates the picture.
Sincerely yours, i
L William H. E11ett, Ph.D.
Chief, Bioeffects Analysis Branch Criteria and Standards Divisica (ANR-460)
Office of Radiation Pmgra=s 2 Enclosures
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Ap ril 2, 1979
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Risk Associated with the PAGs In ter=s cf the average adult individual, a 1 rem whole body exposure carries with it a lifetime cancer risk of between 10 ta 20 fatal cancers per 100,000 adults exposed, and there is an equivalent level of risk of a ocnfatal cancer and of an associated serious genetic effect. For children less than ten years of age, the risk of this exposure is highly uncertain rari,ing frem 10 to liOO fatal cancers per 100,000 children exposed. A 1 re u thyroid exposure due to radiciodine has a corresponding potential thyroid cancer risk of about 2 cases per 100,000 for children and about 1 case per 100,000 for adults.
Perhaps 10% to 20% of these thyroid cancers would be fatal.
Based en 1970 U.S. population statistics, about 20% of the general
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population is less than ten years of age.
For internr.1 organs other than thyroid,1 res of organ exposure has a potential lifetime cancer risk of about 4 per 100,000. The mortality rate of these cancers varies as a function of the specific organ; for lung and bone marrow the mor.-lity is assu=ed to be 100 per cent; for i
t different organs it may be less.
I These cancer risks for me=bers of the general population represent the chance that a cancer will occur in the individual's lifetime.
If the cancer is fatal, the individual lifespan is shortened by an amount ranging from 14 to 30 years depending en the risk model assumed.
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Prepared by:
W. H. Elle t and N. S. Nelsen Criteria & Standards Division
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Office of Radiatica Programs U.S. Environ = ental Protec ticn Agency
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EPA Risk Estimates for Three Mile Island--April 3,1979 These risk estimates are based on the linear non-threshold assumption that any dose of ionizing radiation increases the probability of cancer induc-tion.
The ages and sex distribution of the population at risk are assumed-to be similar to those in the 1970 U.S. population.
As of April 3, 1979, whole body doses to the Pennsylvania population residing in the Three Mile Island area have been estimated as no more than
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2,000 person-rem.
Using the risk coefficients developed by the 1972 BEIR Committee and published by EPA, the estimated lifetime risk of fatal cancer among exposed adults ranges from 0.16 to 0.32 depending on the specifics of 23 4
the risk model employedI~For children less than ten years of age the risk estimates are more uncertain.
Assuming 20 percent of the exposed population is this young, then lifetime risk of fatal cancer ranges from 0.04 to 0.8.
In addition to the estimated risk of fatal cancer discussed above, the estimated incidence of non-fatal cancers would also be increased by a like amount.
Estimates of risk due to possible genetic effects vary widely and cannot be estimated with any certainty.
Genetic risks, based on the 1972 BEIR 5
Committee Report, average about 20 effects per 10 erson-rem with a range of 4 to 100 effects per 10 person-rem.
About 20% of the effects would be expected to occur in the first generation post exposure.
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The 2000 person-rem exposure in the Pennsylvania populatior. might thus lead to 0.4 genetic effects (range 0.08 to 2.0) with 0.08 effects (range 0.025 to 0.4) in the first generation post-exposure.
Prepared by:
W. H. Ellett and N. S. Nelson Criteria & Standards Division Office of Radiation Programs U. S. Environmental Protection Agency
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