radiation risks low dose linearity data, science, regulation and liability
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Radiation RisksLow Dose Linearity
Data, Science, Regulation and Liability
Talk at Association of Physicists in Medicine
San Diego
10:00 a.m. Monday, August 11th, 2003
by
Richard WilsonMallinckrodt Research Professor of Physics
Harvard University
We should start with DataThen use theory (Science)
to fill in gaps
Decide on Aims of Regulation
Discuss Science Policy to meet these aims
Address implementation
DATA comes fromSocietal Mistakes
Atom Bomb (RERF)Excessive medical exposures
industrial exposuresanimal data
Do they fit environmental observations?
These were follow up to 1990. A threshold at 0.1 Sv
(= 10 Rems) is possibleDose was in < a second.
Less effect if dose spread in time
DRRF = 10 (animals)3 (Techa River and Mayak)
2 NCRP and ICRP
Techa River (Kossenko); Sr 90 dose
50 leukemias observed102 expected from RERF
29 backgroundMAYAK workers
early period (Koshurnikova)
“Leukemia” mortality1/3.5 RERF
Could the effect at low doses be worse than
linear?
It was so claimed for the Hanford workers
by Mancuso Stewart and Knealebut
Look at the DATA
Acute Effects
Characteristics• One dose or dose accumulated in a
short time KILLS
• 1/10 the dose repeated 10 times DOES NOT KILL
LINEARITY AT LOW DOSES
IS USUAL!!
Walking blindfold across Michigan Avenue
is safe: (Risk (R) = 0)
IF THERE ARE NO CARS!
The risk (R)
increases roughly in proportion
to the number of cars.
CHRONIC EFFECTS including CANCER
Characteristics
A dose just sub-acute can give effects if repeated.
Usually not all people affected - dose response is flatter
• Low dose linearity is common in societal risks
• Contrast Acute and Chronic Effects
• Radiation Cancers look like other cancers
• 30% of people get cancer
These are enough to set LINEARITY as the DEFAULT
(but only for that cancer)
Some believe in a beneficial effect or radiation at low doses
cf. Low doses of alcohol reduce risk of stroke.
High doses give cancer and narcosis
This is controversial but cannot be excluded
No one knows at low doses
Logical StepsDATA
Scientific Interpretation:APS/ANS/HPS/AAPM
Science policyUNSCEAR/ICRP/NCRPM
Federal RegulatorsDOD/DOE/NRC/EPA/OMB
State RegulatorsPublic Concern
Courts (toxic tort cases)Plaintiff’s Bar/ALF/etc
Legitimate aims (RW)Doses to be less than acute doses
Worker Risk comparable to other worker risks
Public Exposure no larger than accepted fluctuation in BackgroundCost per life in all cases
$200,000 per person Sv (Public)$2,000 per person Sv (worker)
Establish “de minimis” levels 10 (0.1Sv/yr)
Any Firm Limits enough to avoid Legal Liability
ALARA dates from 1928Originally:
“No one should be exposed without expectation of benefit”
(Implicit risk-benefit analysis)
Doses must be reduced: As Low As Practicable (ALAP)
As Low As Reasonably Achievable (ALARA)
As Low As Reasonably Practicable (ALARP)
(note word change without change in understanding)
Assumed whole body dose effects (risk)~ 1965 1 fatal cancer per 10,000 Man - Rems~ 1991 1 fatal cancer per 2,500 Man-Rems
per 25 Person-Sv
Recommended Dose Limits (ICRP; NCRP similar)
When? Public Workers ~1965 500 mR/yr 5 R/yr(expected public average 170 mR/yr)~1991 (guidance) 100 mR/yr 5 R/yr~ 1991 500 mR/5yr 5 R/yr 10 R/5 yr‘91 NCRP 1R x age
Note that if a large group of workers received the maximum, effects would just be detectable (above background) at age 80
Conservatisms
Theory for low doses (<10 rems in RERF)
Dose Rate Response Factor = 2
(data on leukemia says 3;
animal data range to 10)
Cost to reduce a risk used as a minimum not a maximum
‘de Minimis” guidelines used as regulation
Radiation Risk should be comparable to other Occupational Risks
Annual Risk per 100,000Actual (av over all workers):
All Industries 7manufacturing 3Coal mining 24
Maximum (theory): ICRP 5 yr av. 80
but average worker gets about 1/5 of ICRP maximum
What Dose Parameter?Average over 1/4 to full lifetimeWhy regulate over 1/4 year?
What about contract workers?
Worker should control his exposure
Public? Liability for LawsuitsRemember old rule: Average
over public is what matters most
Be Prepared!If someone sues you:
Have all data and justification readyHelp stop frivolous
lawsuits
No. 98-56157 In the Supreme Court of the United States
JOE KENNEDY, et al. Plaintiffs-Appellantsv.
SOUTHERN CALIFORNIA EDISON COMPANY and COMBUSTION ENGINEERING
On Writ of Certiorari to the United States Court of Appeals for the First Circuit
BRIEF OF AMICI CURIAE
ROBERT K. ADAIR, BRUCE N. AMES, D. ALLAN BROMLEY, PATRICIA A.
BUFFLER, BERNARD COHEN, BERNARD GITTELMAN, SHELDON LEE GLASHOW,
MICHAEL GOUGH, RONALD HART, DUDLEY HERSCHBACH, LAWRENCE
LITT, A. ALAN MOGHISSI, RODNEY W. NICHOLS, ROBERT V. POUND, NORMAN RAMSEY, JOSEPH P. RING, FREDERICK SEITZ, EDWARD THORNDIKE, LYNN H.
VERHEY and JAMES D. WATSON
IN SUPPORT OF DEFENDANTS-APPELLEES' MOTION FOR REHEARING AND REHEARING EN BANC
Kennedy worked at San Onofre Nuclear plant
Some workers brought “fuel fleas” homeKennedy claimed his wife got Leukemia
from a fuel flea he brought home.No evidence he brought one homeUncontroverted evidence that the
maximum dose from the largest possible fuel flea gave a risk of 10-7
(Probability of Causation 10-5) 3 week trial
Appeal originally allowed by 3 judge panel.
The appeal was reversed, and the plaintiffs blamed it on ALF!
(Where was AAPM? Health Physics Society? NCRPM)
My website:http://phys4.harvard.edu/~wilson/
Page on radiation references/resource_letter.html
pages on Russian Chernobyl dataradiation/radiation_and_risk.html
Techa Riverpublications/pp747/techa_cor.htm
Wilson and CrouchRisk Benefit Analysis
Riskad.html
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