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

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